Advertisement

The Lowlands and Midlands of Northwestern Atlantic Iberia

  • Javier Amigo
  • Manuel Antonio Rodríguez-Guitián
  • João Jose Pradinho Honrado
  • Paulo Alves
Chapter
Part of the Plant and Vegetation book series (PAVE, volume 12)

Abstract

The Iberian Cantabrian Atlantic biogeographical territory is a narrow strip of land, fallen L-shaped, which runs parallel to the coast from Pamplona (Spain) to near Aveiro (north Portugal), characterized by a wet and warm climate, with smooth winters and slight or absent drought in summer. Its relief is very varied and includes from coastal and inland plains to mountainous terrains with altitudes up to 1700 m. Homo sapiens has been present in this territory since the Upper Pleistocene but its influence on vegetation cover seems to have been very low until the Climate Optimum of the Holocene. Since this period human activities increased progressively and led to a wide deforestation of the territory, the expansion of non-arboreal seral communities and, during the last century, the introduction of a great variety of alien species for timber production and ornamental use. In spite of this great influence of man on the vegetal cover of the territory, some facts reveal its similarity to the rest of Atlantic Europe: (1) Supremacy of deciduous forests dominated by pedunculate oak and beech which are replaced by ash, maple, elm and linden trees in mixed forests, or alder, birch and willow in alluvial forests. (2) Replacing forests, seral scrub of thorny bushes or broom scrub (Cytisus sp. pl.) occur, with further degradation giving way to heathlands dominated by ericoid species but also with gorses (Ulex sp. pl.) and other thorny leguminosae (Genista sp. pl.). (3) Several types of meadows and other grasslands play a relevant role in the landscape and in traditional agricultural systems. (4) Different vegetation complexes typical of sandy deposits, rocky coasts and saltmarshes merge along its extensive shoreline. Nevertheless, there is a particular fact that differentiates these Atlantic territories from others located further north: the existence of many examples of evergreen vegetation, such as forests of holm oak (Quercus ilex, Q. rotundifolia), cork oak (Quercus suber) and laurel tree (Laurus nobilis), or scrub dominated by Arbutus unedo or Phillyrea sp. pl., due to their proximity to the Mediterranean Region.

6.1 Introduction

The territory described in this chapter is a land strip with a varying width, running parallel to the north and northwest coast of the Iberian Peninsula. Overall, it covers about 55,000 km2, including the following administrative regions and provinces, from east to west (Fig. 6.1)
  • Navarre, approximately its northwest corner until its capital Pamplona;

  • Basque Country: the whole provinces of Guipúzcoa and Vizcaya, and roughly half the province of Álava;

  • Cantabria and Asturias: the northern areas (60–70%) of these two regions, both holding only one province; the southern areas correspond to the mountains of the Cantabrian Range, which are included in a distinct biogeographic unit (see Chap.  7);

  • Galicia, with roughly 26,000 km2, is the region contributing the largest area, including two full provinces (A Coruña and Pontevedra) and a large part of the provinces of Lugo and Ourense; the highest mountains of these two provinces, at the borders with Asturias and Castile, are excluded and are also treated in Chap.  7;

  • Portugal is represented by its northwest corner, including the whole provinces of Minho and Douro Litoral, a small neighbouring part of Trás-os-Montes, and part of Beira Litoral down to Serra do Buçaco, which is considered the southern limit of the European-Atlantic biogeographic province.

Fig. 6.1

Delimitation of administrative territories included in this chapter

This land extension is shaped like a capital “L”, rotated clockwise by 90°, with the shortest arm wider than the longest one. However, the linear distance to the Atlantic shoreline is hardly larger than 120 km.

6.1.1 Geomorphology and Soils

The geological substrates that characterize this territory include rocks of a rather variable age (>1100–2 million years). From a lithological perspective, this land mass is characterised by: the predominance of carbonate-rich rocks (limestones, dolomites, marls), alternating with siliceous metamorphic substrates (shales, slates, sandstones, quartzites) and some granite outcrops of various ages, in the centre-eastern half (centre-eastern Asturias, Cantabria, Basque Country and northern Navarre); the massive presence of palaeozoic metamorphic rocks (phyllites, slates, sandstones, quartzites, gneisses) in western Asturias and eastern Galicia; and the dominance of schists, gneisses and granitoids (leucogranites, diorites, syenites), along with several outcrops of alkaline (amphibolites, gabbros, eclogites) and ultramaphic (peridotites, granulites) rocks, in some cases serpentinized rocks, in western Galicia and northern Portugal (Vera 2004).

The topography is closely linked to this distribution of bedrock types, resulting from the collision of the Iberian and European tectonic plates during the Alpine orogeny. This process has deformed and raised palaeozoic substrates, already deformed by the Variscan orogeny and multiple erosive cycles. Later, several distensive phases have created numerous depressions within the mountainous ranges. Those depressions were filled with sediments during the second half of the Mesozoic and the Cenozoic. Examples of these are located south of the Basque-Cantabrian mountains (Llanada de Álava), the endorheic basin of Oviedo, and the depressions of inland Galicia (Terra Chá, Terra de Lemos, Val de Maceda). This territory has been affected by nival and periglacial phenomena, also in the coastal lowlands, during the cold periods of the Pleistocene. Glaciers were even formed in the main mountain ranges. During interglacial periods sea level rise allowed the formation of large marine deposits (rasas), currently located at a certain elevation above sea level.

Overall, the terrain morphology is more complex in the eastern half of the territory, due to the highest intensity of crustal deformations and to the largest variety of bedrock types with different resistance to erosive processes. In northern Navarre and eastern Basque Country there is the contact between the Pyrenees and the Basque-Cantabrian mountain range. The latter are oriented east-west and are considered the connection between the Pyrenees and the Cantabrian mountain range, with summits of over 1500 m (Ortzainzurieta 1570 m, Castro Valnera 1696 m). The Cantabrian Range dominates western Cantabria and Asturias, with many summits over 2000 meters. From the Cantabrian Range, several minor mountain ranges extend towards the north and into the Cantabrian Atlantic territories, often with summits above 1000 meters. The morphology of this sector includes sub-coastal hills and mountains, and coastal flatlands alternating with capes of resistant substrates (quartzites, marbles). When it reaches Galicia, the Cantabrian Range splits into two ridges. The northern one develops towards NNW, reaching the northern Galician mountains. The southern ridge, already outside Cantabrian Atlantic territories, surrounds the western part of the El Bierzo depression. The mountains of northern Galicia hold summits between 600–1000 m, close to the coast, and from their central sector a succession of north-south oriented mountains, known as the Dorsal Gallega, develops down to the valley of the river Miño. Southwards, at the border with Portugal, several mountains occur, from the Xurés/Gerês range (1538 m) to the Peneda, Alvão and Marão mountains, also reaching 1300–1400 m elevation. The Atlantic coast of Galicia is characterised by several “rías”, separated by hill ranges (500–600 m) extending into the sea through a series of prominent capes and small archipelagos (Sisargas, Lobeiras, Sálvora, Ons, Cíes) (Fig. 6.2).
Fig. 6.2

Lower areas close to sea have supported for centuries high population levels not compatible with a well conserved vegetation cover. North side of Ría de Arousa from A Curota (A Coruña, Galicia)

The boundaries of the main fluvial basins follow the divides of the Basque Mountains, the Cantabrian Mountains and the Galician-Portuguese Mountains. Between the Bidasoa River, ending at the border between Spain and France, and the Sor River, ending at the border between the provinces of A Coruña and Lugo, the rivers run to the Gulf of Biscay over short distances (the longest one, the Nalón River, is the only one over 100 km long). Towards the west, the main rivers draining into the Atlantic Ocean (Tambre, Ulla, Limia/Lima) are more than 100 km long, with the Miño/Minho reaching 350 km and the Duero/Douro 897 km. The Cantabrian Atlantic territories draining towards the Mediterranean comprise only small areas in the heads of the rivers Ebro and Zadorra.

The main processes of soil formation under the wet temperate climate that prevails in most of the territory are leaching of base cations, due to abundant rainfall, and organic enrichment on the upper layers resulting from the abundant biomass decaying from vegetation every year. For these reasons, the soils are usually acidic, especially when soils are formed from siliceous metamorphic materials, granitic rocks, or sediments derived from these. Often, soils formed on these materials in the highest mountains show a limited development and signs of podsolization, especially if developed on quartzites, sandstones, or leucogranites. In these areas, peatlands are frequent whenever topographic and moisture conditions are favourable. Nonetheless, in the less evolved soils (leptosols, umbrisols) on bedrocks providing abundant Ca or Mg, such as limestone, carbonated clays or serpentine rocks, pH values in the upper layers are kept close to neutral, even at locations with an annual rainfall above 1500–1700 mm. The soils of flat areas often present features derived from seasonal flooding (gleysols), especially when developed on fine textured sediments (vertisols).

6.1.2 Climatic Conditions

Due to the geographic rationale described above, climatic conditions throughout the area can be described based on two words: atlanticity and oceanity. This translates into climates with abundant rainfall, even in summer, due to the dominance of northern winds, and a narrow yearly temperature range. According to the bioclimatic classification of Rivas-Martínez, most of the Cantabrian Atlantic territory is included in the thermotemperate, mesotemperate and supratemperate climatic belts.

The mesotemperate is clearly the predominant belt, whereas the two other temperate belts are unequally distributed towards east and west. In the Cantabrian and Basque and North Galicia and Asturias sectors, the supratemperate is the second most frequent belt, with the thermotemperate limited to a very narrow strip along the coast and to isolated patches towards the east. Inversely, in the Galician and North Portugal sector, the second most widespread belt is the thermotemperate, whereas the supratemperate is limited to the scattered mountain ranges. The supratemperate belt again becomes remarkable in the North Lusitania Sierran sector.

In terms of ombroclimate, the most widespread regime is the humid belt, followed by the hyperhumid. Again, hyperhumid areas are more common towards the east. Nonetheless, in all four sectors there are records of mountain areas in the hyperhumid and even ultrahyperhumid belts. But there are also areas with lower rainfall values, in the subhumid belt, in the southern part of the Cantabrian and Basque sector and in inland stretches of wide fluvial valleys of the Galician and North Portugal sector.

The position of a bioclimatic border with the Mediterranean climate that characterizes most of this Atlantic territory, explains the fact that different parts of it hold some deficit in terms of summer rainfall. This shortage may last for two or even three consecutive months in summer, but in most cases it is compensated by spring rainfall and so the level of drought is not as high as the one recorded under the Mediterranean climates. This climatic peculiarity is called the Submediterranean variant of the Temperate climate, and it is quite widespread throughout the North Lusitania Sierran and Galician and North Portugal sectors, gradually disappearing towards the northern and eastern sectors. This variant also occurs in the southernmost subsector (Navarre and Álava área) of the Cantabrian and Basque sector. There are small portions of the territory that do hold a Mediterranean bioclimate (specifically in the mesomediterranean belt), in the Sil valley of inland Galicia and in the southern lowlands of the Galician and North Portugal sector. There are several publications with detailed maps of the thermo- and ombroclimatic belts for most of the territory (Loidi and Báscones 2006; Rodríguez-Guitián and Ramil-Rego 2007; Loidi et al. 2011; Monteiro-Henriques et al. 2015).

The oceanic character is another climatic peculiarity of all this territory, increasing towards areas that are located closer to the sea and at lower elevations. In fact, there are very few climatic stations along the coast between A Coruña and Guipúzcoa holding continentality indices above 10 units (measured as annual temperature ranges, according to the models of Rivas-Martínez), which are the lowest values across all of the Iberian Peninsula.

6.1.3 Biogeography

All the area is included in the Atlantic European province and, within it, in the Cantabrian Atlantic and Atlantic Orolusitania subprovinces. This is the southwest limit of the Eurosiberian region. This territory, stretching towards the north through French Aquitaine, is limited in the east, in its Spanish part, by another large biogeographic unit, the Cévennean-Pyrenean province, which begins in northeast Navarre. Towards the north and west, the limit is defined by the Atlantic Ocean throughout 2560 km of coastline. The southern limits are defined by its contact with the Mediterranean region in the eastern part (Navarre, Basque Country and Cantabria) and with the Orocantabric subprovince and the Galician-Leonese mountains (Chap.  7), from western Cantabria to eastern Galicia, from where the limit is again defined by the Mediterranean region, through northern Portugal down to the southwestern end of the province.

Together, the geomorphologic, climatic and biogeographic features define a favourable territory for hosting a flora with evident similarities to that of the remaining Atlantic and Central-European areas. The floristic peculiarities that discriminate these Iberian Cantabrian Atlantic lowlands from those territories north of the Pyrenees can be summarized as follows:
  • It has a remarkable component of the Iberian endemic flora, especially in two environments: the coastal habitats with taxa that became specialized to ecologically demanding biotopes, such as cliffs and dunes; and the supratemperate areas that provide habitats for the Pyrenean-Cantabrian flora.

  • The proximity to the Mediterranean region has allowed the occurrence of numerous taxa with that origin among the Cantabrian Atlantic flora, taking advantage of favourable biotopes.

The biogeographic subdivision that will be used here is based on the proposals by Rivas-Martínez in their most recent version (Rivas-Martínez et al. 2014). Accordingly, we divide the territory into four sectors, from east to west: Cantabrian and Basque, North Galicia and Asturias, Galician and North Portugal and North Lusitania Sierran. In turn, for greater precision in the distribution of plant communities and their vegetation series, we divide these sectors into subunits, as already used by Rivas-Martínez in previous classifications (Rivas-Martínez 2007) with the rank of sub-sector; these subunits in the most recent proposal are classified in the category of “territories”.
  • The Cantabrian and Basque sector, which includes the eastern one-third of the total area and includes three subunits: the East Basque territory, including the western peaks of the Pyrenees down to the coast and most of Guipúzcoa from the coast up to the Basque Mountains; the Santanderian-Biscayan territory, corresponding to the lowland and coastal areas of Vizcaya and Santander; and the Navarran and Alavese territory, south of the two previous ones and less oceanic since it does not reach the Cantabrian coast.

  • The North Galicia and Asturias sector, subdivided in: the Central-East Oviedo territory, covering the eastern half of Asturias (starting in the catchment of the river Narcea) and western Cantabria; and the North Galician-Asturian territory, which includes northern Galicia and the northern Atlantic catchments down to the river Eume.

  • The Galician and North Portugal sector, including three subunits: the North Galician-Portuguese territory, covering most of Galicia draining to the Atlantic ocean, the South Galician-Portuguese territory, from the valley of the river Miño/Minho, at the border between Portugal and Spain, south to the vicinity of Aveiro, at the southwestern end of the Eurosiberian region; the Inner Galician territory, partially under mediterranean bioclimate, which includes two stretches of river valleys particularly interesting for their special thermal conditions: the Sil river which flows east-west until its junction with the Miño and supports mostly a Mediterranean-type bioclimate, and the Navia river representing a refuge for thermo-xericity despite emptying into the Cantabric Sea.

  • The North Lusitania Sierran includes the mountains with the highest altitudes of northwest Portugal and some bordering with Galicia: Peneda, Gerês-Xurés, Larouco, Cabreira, Alvão and Marão. All these serras, previously considered within the Galician and North Portugal sector, form the Eurosiberian/Mediterranean chorologic border.

6.2 Human Influence

The European landscape has been conditioned since antiquity by the biological and cultural development of men. While during the Paleolithic those changes were mainly located along the Cantabrian Atlantic coast, with the use of fire and the predation on certain species. In the Holocene various agricultural and pastoral techniques were adopted. The footprint on the vegetation and landscape became increasingly clear: new species previously domesticated in Fertile Crescent were introduced and spread, while the destructive action on pristine ecosystems increased by the use of fire, land ploughing and extensive use of livestock. (Fig. 6.3)
Fig. 6.3

Deforestation of more fertile lands is a consequence of human activities since Neolithic times. The “Alsasua corridor” from Puerto de Pagoeta (Álava). The arboreal vegetation in the foreground is a basophilous beech woodland (Carici sylvaticae-Fagetum sylvaticae). Down slope it borders on mesophytic Navarran-Alavese pedunculate oak woodlands (Crataego laevigatae-Quercetum roboris). In the background, extensive crop fields occupy lands covered by these latter oak woodlands many centuries ago

Possibly these practices favoured the expansion of nitrophilous communities associated with roads in shady environments (alliances Aegopodion podagrariae, Galio aparines-Alliarion petiolatae, Balloto foetidae-Conion maculati, Bromo ramosi-Eupatorion cannabini from the class Galio aparines-Urticetea maioris) and cleared areas subject to regular trampling of human beings and livestock (alliances Arction lappae, Onopordion acanthii, Cirsion richteriano-chodati, class Artemisietea vulgaris). At the same time there was the expansion of nitrophilous shady communities associated with forest clearings caused by logging and wildfires (alliances Atropion belladonae and Carici piluliferae-Epilobion angustifolii, class Epilobietea angustifolii).

Approximately 5000 years ago, semi-nomadic groups of humans began to organize in villages initiating the process of ruralizing the territory. There was an increase of land devoted to cultivation and livestock grazing at the expense of the area occupied by the original vegetation. There was a loss of woodlands, especially in territories near the coast, resulting in an open landscape where cultivated and managed areas were more common. This was the landscape that the Romans found upon arrival in these territories and that stayed during their rule.

In this period there was an expansion of plant communities adapted to certain recurring disturbances caused by human activities, such as those associated with rainfed cereal crops cultivation, road verges communities (alliances Scleranthion annui and Sisymbrion officinalis, class Stellarietea mediae) or nitrophilous communities growing in places of accumulation of organic litter (alliance Saginion procumbentis, class Polygono-Poetea annuae). The most characteristic species of this type of vegetation would be present in the different territories where human groups settled, but others quite possibly were introduced. It is very difficult to exactly establish now what the original source of this flora was.

The collapse of the Western Roman Empire (476 AD) marked the beginning of a period of strong political instability, in which these territories were overrun by various Germanic groups and then by the Muslims, and later by the Christian kingdoms. In some cases, those periods of instability led to the recovery of forest cover, but afterward, human actions increased in those territories and agricultural and pastoral activities had an important development at that time, generating cultural landscapes that persisted for centuries. At that historic moment we would have to place the establishment of numerous meadow plant communities (alliances Arrhenatherion elatioris and Cynosurion cristati of the class Molinio caeruleae-Arrhenatheretea elatioris) and the expansion of grasslands through extensive grazing of pastures in low (alliance Lolio perennis-Plantaginion majoris) and mountain areas (alliances Violion caninae and Campanulo herminii-Nardion strictae, class Nardetea strictae).

In the late fifteenth century, the Portuguese and Spanish began the exploration and colonization of the northern coasts of Africa and the East and West Indies. As a result of these actions, new species were progressively introduced in the Cantabrian Atlantic area as food, fiber, beverages or wood sources, as healing medicines or for ornamental purposes. The effects of this neophyte contingent are now evident either by replacing in many areas the floral elements coming from the Fertile Crescent, or affecting the many naturalized species of flora and fauna that have adapted successfully to the native natural and semi-natural habitats.

The course of action of human communities in nature was also modified with the development of the Industrial Revolution, by the mechanization of many activities previously done manually or with the help of animal power, with the emergence and use of agrochemicals such as fertilizers, and finally with the incorporation of genetically engineered organisms transformed by hybridization, artificial selection, transgenesis and cisgenesis.

As a result of the cultural changes mentioned, the current characteristics of the vegetation cover of the Cantabrian Atlantic territories can be summarized as:
  • A significant reduction in the area covered by forests (Fig. 6.4) in the lowlands and less remote areas and a floristic and structural simplification of the woodland communities in the areas with a more intensive management. (Fig. 6.5)
    Fig. 6.4

    Remains of xerophilous holm oak woodlands (Genisto hystricis-Quercetum rotundifoliae) and its mantle vegetation (Erico scopariae-Arbutetum unedonis) growing between vineyards on steep slope terraces in a mesomediterranean valley of Inner Galicia. Ribeira Sacra, Valle del Sil (Lugo)

    Fig. 6.5

    Ancient management of woodlands to gather timber and fruits has led frequently to simplified (often monospecific) canopy woodlands, with a cleared up understory dominated by trivial species. Old chestnut (Castanea sativa) woodland at Torbeo (Lugo, Galicia)

  • The regional extinction in some cases and a range reduction in others, of different tree species by anthropic causes.

  • A remarkable expansion of the area occupied by shrub seral communities.

  • The emergence and spread of segetal and ruderal communities related to agro-pastoral activities and road verges.

  • The either conscious or casual introduction of a large set of plant invasive species. (Fig. 6.6)
    Fig. 6.6

    Land uses in oceanic Cantabrian-Basque mountains. Gentle slopes near the villages are covered by alien conifer plantations (Pinus radiata, Larix kaempferi, etc.); far and less accessible terrains are still covered by deciduous woodlands, mainly dominated by beech (Fagus sylvatica). The tops of the mountains have grasslands grazed by sheep flocks in summer. North slope of the Sierra de Aralar (Guipúzcoa, Basque Country)

  • A substantial increase in the area occupied by forest plantations of exotic species of rapid growth and intensive management which causes serious ecological problems and modifications in ecosystems services (increased erosion, soil depletion, hydrological alterations, changes in composition and diversity in animal and plant species, etc.).

6.3 Native Forests and Mantle Vegetation

In the following description of forests occurring in this biogeographic unit, we distinguish between climatophilous forests and edaphohygrophilous forests.

6.3.1 Climatophilous Forests

These forests grow on well drained soils and their floristic composition is mainly determined by climate (thermotypes, ombrotypes), topography (aspect and solar radiation) and soil nutrient content (nutrient-poor soils derived from granites or siliceous metamorphic substrates vs. more fertile soils derived from carbonated rocks or, less often, from basic and ultrabasic bedrocks).

The macroclimatic conditions prevailing in this biogeographical unit favour the predominant development of forests belonging to class Querco-Fagetea sylvaticae, with a canopy dominated by deciduous species of the genera Quercus and Fagus. In certain situations, other genera that include deciduous species (Betula, Castanea, Acer, Fraxinus, Ulmus, Prunus, Tilia, Carpinus, Celtis) or mesophytic evergreen species (Ilex aquifolium, Taxus baccata, Prunus lusitanica) can reach considerable abundances in the canopy. Still, local factors such as a reduction in summer rainfall or the occurrence of soils with little development and water retention capacity will favour the presence of forests dominated by marcescent species (Q. pyrenaica, Q. faginea, Q. pubescens) or even by xerophytic evergreen species (Q. ilex, Q. rotundifolia, Q. suber, Arbutus unedo).

The elevation sequence of the main thermotypes (from the upper thermotemperate to the upper supratemperate) has a related diversity of forest types. The areas along the Cantabrian and Atlantic coasts (thermotemperate and lower mesotemperate thermotypes) host forests of a thermophilous nature, rich in evergreen species (Arbutus unedo and Laurus nobilis throughout the territory; Quercus suber, Myrtus communis or Phillyrea angustifolia toward its southwest end) as well as climbers (Clematis vitalba, Hedera hibernica, H. helix, Lonicera periclymenum, Smilax aspera, Tamus communis), that can penetrate through the valleys up to elevations of 400/500 m in coastal areas, or even 700/800 m in the inland flatlands and valleys. The native forest communities most frequent on siliceous soils of these bioclimatic belts are oak forests of Quercus robur, often with chestnut (Castanea sativa) and birch (Betula pubescens subsp. celtiberica) (alliance Quercion pyrenaicae). The associations with the widest occurrence in this territory are the Hyperico pulchri-Quercetum roboris in the Cantabrian and Basque sector, the Blechno spicant-Quercetum roboris in the North Galicia and Asturias sector, and the Rusco aculeati-Quercetum roboris in the thermo-mesotemperate, North Galician-Portuguese areas of Galicia and northern part of northwest Portugal (Izco et al. 1990a; Díaz-González and Fernández-Prieto 1994; Loidi et al. 1997a; Honrado 2003) (Fig. 6.7). In the South Galician-Portuguese territory, the Viburno tini-Quercetum roboris represents the transition between the Atlantic oak forests and the Mediterranean sclerophyllous forests (Rivas-Martínez 2011; Costa et al. 2012).
Fig. 6.7

Deciduous oak forests only cover wide surfaces in the least disturbed Cantabrian Atlantic landscapes. Acidophilous Cantabrian-Basque oak woodland (Hyperico pulchri-Quercetum roboris) at Iribas (Guipúzcoa, Basque Country)

Within this same thermoclimatic belt, oak forests developed on fertile soils hold a higher canopy diversity, due to varying abundances of other meso-hygrophilous tree species, such as ash (Fraxinus excelsior, Fraxinus angustifolia), hazel (Corylus avellana), maple (Acer pseudoplatanus, Acer campestre), Carpinus betulus (exclusively at a few East Basquean locations), Alnus glutinosa, Ulmus minor or Celtis australis. In the eastern half of the territory these forests are included in two main associations: the Polysticho setiferi-Fraxinetum excelsioris in the Central-East Oviedo surroundings and in the Cantabrian-Basque areas draining to the Cantabrian Sea, and the Crataego laevigatae-Quercetum roboris in the Navarran-Alavese areas (Díaz-González and Fernández-Prieto 1994; Loidi et al. 1997a, 2011). In the western areas, a single association has been described so far, distributed across the hilly and mountainous areas of the South Galician-Portuguese territory (Hyperico androsaemi-Quercetum roboris, Honrado et al. 2002); however, forests with this type of ecology occur in several areas of northern and central Galicia (Rodríguez-Guitián 2005). All these community types are included in the alliance Pulmonario longifoliae-Quercion roboris, vicarious of the centre-european Carpinion betuli.

Spread among these predominant forest types, others can be observed at locations with specific climatic or edapho-topographic conditions: holm oak forests of Quercus ilex on carbonated lithosols close to the coast and of Q. rotundifolia in the inland sheltered valleys (alliance Quercion ilicis, class Quercetea ilicis); beech forests on steep slopes facing north, at locations with a high cloudiness and summer rainfall, especially in the eastern half of the territory (Ilici aquifolii-Fagion sylvaticae); and oak forests of Q. pyrenaica on siliceous sandy soils (Melampyro pratensis-Quercetum pyrenaicae, Lonicero periclymeni-Quercetum pyrenaicae; alliance Quercion pyrenaicae), or when on calcareous soils, dominated by Q. faginea (Pulmonario longifoliae-Quercetum fagineae) or Q. pubescens (Roso arvensis-Quercetum pubescentis), included in the alliance Quercion pubescenti-petraeae, in areas with some summer drought at some distance from the coast (Díaz-González and Fernández-Prieto 1994; Loidi et al. 1997a, 2011; Díaz-González 2010a).

The Cantabrian Atlantic areas with the lowest rainfall values are located in the mid and lower segments of the river Sil, the main tributary of the river Miño, where total annual rainfall is not higher than 800 mm. Here, the steepest and sunniest slopes host holm oak woods (Genisto hystricis-Quercetum rotundifoliae) and cork oak forests (Physospermo cornubiensis-Quercetum suberis), which become more widespread towards the east, in the municipalities of Valdeorras and El Bierzo, with a pronounced rain shadow effect (Rivas-Martínez et al. 1984; Rivas-Martínez 1987; Romero-Buján 1993; Izco et al. 1990b). Cork oak forests are also present, although less frequently, in the valley of the river Navia (Asturias/Galicia) and in several localities of inland Cantabria and coastal Basque Country (Aedo et al. 1991; Aseginolaza et al. 1989; Díaz-González 2010a). Nonetheless, all these evergreen forests are under strong oceanic (atlantic) influence, as revealed by the presence of species such as Quercus robur, Glandora prostrata, Daboecia cantabrica, Holcus mollis, Stellaria holostea, Teucrium scorodonia, etc. (Figs. 6.8 and 6.9)
Fig. 6.8

Even though the Cantabrian Atlantic territories of Iberia are affected by a pre-eminent oceanic climate, many “islands” of woodlands dominated by different typical Mediterranean Fagaceae can be found. Marcescent basophilous Quercus faginea woodland (Pulmonario longifoliae-Quercetum fagineae) on limestone; south facing slope at the Sierra de Aralar (Navarra)

Fig. 6.9

Another example of Mediterranean woodland vegetation, the mesophytic cork-oak woodland (Physospermo cornubiensis-Quercetum suberis) at the river Sil valley in Valdeorras (Ourense, Galicia)

Throughout this territory with low elevations and close to the coast it is possible to find fragments of other types of forests, often in mosaic with the previous ones. Those forests develop at sites with soil conditions that are not adequate for deciduous oaks (Quercus robur, Q. petraea) or for beech (Fagus sylvatica): sheltered, shady slopes with rocky soils or abundant rock outcrops. These biotopes are occupied by a wide set of tree species that are infrequent in the previous forest types, such as limes (Tilia platyphyllos, T. cordata), wych elm (Ulmus glabra), maples (Acer pseudoplatanus, A. platanoides), wild cherry (Prunus avium) and ashes (Fraxinus excelsior, F. angustifolia). In recent years several types of these mixed forests occurring on slopes or cliffs in the northern Iberian Peninsula have been described (Rivas-Martínez 2002a; Costa et al. 2012; Biurrun et al. 2011), and included within the alliance Tilio platyphylli-Acerion pseudoplatani, revealing their highly variable floristic composition throughout the territory. The Hyperico androsaemi-Ulmetum glabrae occurs in Cantabrian-Basque siliceous areas (Biurrun et al. 2011), whereas the Fraxino angustifoliae-Ulmetum glabrae is found in inland mountainous areas of northern Portugal included in the North Lusitania Sierran sector (Monteiro-Henriques et al. 2010). Other authors have published data on similar communities from several locations in Galicia (Amigo et al. 1994; Rodríguez-Guitián et al. 2000; Rodríguez-Guitián 2005).

The areas located in the upper mesotemperate and supratemperate thermotypes host a lower diversity of forest types due to the colder temperature regimes. Beech forests are remarkable for their ecological amplitude and vitality, occurring on siliceous (alliance Ilici aquifolii-Fagion sylvaticae) as well as limestone soils (alliance Fagion sylvaticae), and being dominant in mountain areas above 800/900 m in the eastern part of the territory. Toward the west, beech forests become increasingly less frequent in the Cantabrian Atlantic territories, although along the Orocantabrian mountain range they maintain their continued presence until its western end. The current western limit of these forests in the Atlantic fringe of Europe is represented by the beech woods in the upper catchment of the river Eo (Lugo, Galicia) (Rodríguez-Guitián et al. 2001). The diversity of beech forests has been described as follows:
  • association Saxifrago hirsutae-Fagetum sylvaticae: Cantabrian and Basque sector on siliceous substrates (Loidi 1983; Loidi et al. 1997a)

  • association Saxifrago spathularis-Fagetum sylvaticae: Central-East Oviedo and North Galician-Asturian territories on siliceous substrates (Rodríguez-Guitián et al. 2003; Rodríguez-Guitián 2005, 2006)

  • association Carici sylvaticae-Fagetum sylvaticae: Cantabrian and Basque sector on limestone/carbonated substrates (Loidi et al. 1997a, 2011)

  • association Carici caudatae-Fagetum sylvaticae: Central-East Oviedo territory on limestone/carbonated substrates (Rivas-Martínez 2011)

  • association Epipactido helleborines-Fagetum sylvaticae: Navarran-Alavese and East Basque territories on limestone/carbonated substrates (Berastegi et al. 1997a; Loidi et al. 1997a, 2011). (Figs. 6.10 and 6.11)
    Fig. 6.10

    Common beech woodlands are more frequent and extensive in the central-eastern part of the territory but still are present as small woods in NE Galicia. Calcicolous beech woodlands (Carici sylvaticae-Fagetum sylvaticae) on limestone (foreground) and silicicolous beech woodlands (Saxifrago spathularis-Fagetum sylvaticae) on slates and quartzites (background); Saja Valley (Cantabria)

    Fig. 6.11

    Fern-rich understory in a mesotemperate acidophilous North Galician-Asturian beech woodland (Saxifrago spathularis-Fagetum sylvaticae); Belmonte (Asturias)

As the importance of beech forests decreases in the landscapes of meso-supratemperate areas, that of oak forests increases, especially in the case of Quercus robur. Typical sub-associations of both the Blechno spicant-Quercetum roboris and Rusco aculeati-Quercetum roboris, and the association Vaccinio myrtilli-Quercetum roboris occupy these belts in siliceous areas of the North Galician-Asturian, North Galician-Portuguese and North Lusitania Sierran sectors, respectively (Izco et al. 1990a; Costa et al. 1998a). The mountains of inner Cantabria and Álava host forests of Quercus petraea on siliceous soils (association Pulmonario longifoliae-Quercetum petraeae, alliance Ilici aquifolii-Fagion sylvaticae) (Loidi et al. 1997a).

With a much wider distribution, short-sized forests of Ilex aquifolium (alliance Ilici aquifolii-Fagion sylvaticae) occur at the edges of beech and oak forests, in areas that are grazed by cattle and sheep (Aseginolaza et al. 1989; Aedo et al. 1991; Rodríguez-Guitián 2005). Also scattered throughout the mountains in the territory are the small woodlands of Taxus baccata, which hold a remarkable biogeographic significance (Fernández-Prieto and Díaz-González 2003; Díaz-González 2010b; Ihobe 2011; Rodríguez-Guitián et al. 2010).

With a very localized and fragmented distribution, in the highest mountains with edaphic conditions unsuitable for beech or oaks, forests can be dominated by birch (Betula pubescens subsp. celtiberica) and rowan (Sorbus aucuparia), related to frequent snowfall (Herrera 1995; Rodríguez-Guitián 2005). These forests resemble those that are common in the upper supratemperate areas of the Orocantabrian siliceous mountains, which are included in the alliance Ilici aquifolii-Fagion sylvaticae.

When the forests described above suffer regeneration processes, opening of clearings due to natural phenomena (storms, avalanches, landslides, etc.) or to human logging, woody formations dominated by fast-growing tree species can develop (pre-climax forests and edge woodlands). These formations maintain the nemoral conditions required by the flora typical of mature forests while such mature forests do not regenerate at those spots. Under certain conditions, similar formations can occur spontaneously, as permanent communities, at the edges of forest patches when these reach areas that are not suitable for their characteristic dominant trees, such as soils with abundant rocks or low water retention capacity. They can also develop on former farmland that has suffered abandonment.

Similar to the mature forests they replace, these pre-climax forests and edge woodlands hold physiognomic and floristic features that differ depending on whether they occur on climatic or topo-edaphic conditions. In general, pre-climax forests on siliceous soils are dominated by heliophilous species with low nutrient demands (Salix atrocinerea, Betula pubescens subsp. celtiberica, Sorbus aucuparia) or by species with a high capacity to resprout (Corylus avellana, Ilex aquifolium). These communities are included in the Betulion fontqueri-celtibericae alliance, such as the Cantabrian-Basque association Rhamno frangulae-Betuletum celtibericae or the North Galician-Asturian and North Galician-Portuguese Holco mollis-Betuletum celtibericae (Amigo and Romero-Buján 1998; Berastegi et al. 1997b). Often the regeneration of Cantabrian Atlantic silicicolous forests over heathland and broom scrub includes a community dominated by Frangula alnus and Pyrus cordata (Frangulo alni-Pyretum cordatae association), included in the alliance Frangulo-Pyrion cordatae (class Rhamno cathartici-Prunetea spinosae) (Herrera et al. 1991). On limestone soils, the elimination of the dominant trees (ash, oak, maple, beech, lime) favours the formation of small, closed woodlands dominated by Corylus avellana and Crataegus monogyna (Betulion fontqueri-celtibericae alliance) (Amigo et al. 1994). These pre-climax forests can be replaced by thorn scrub which most often include Crataegus monogyna and Prunus spinosa, as well as several species of the genera Rubus and Rosa (alliance Pruno-Rubion ulmifolii, class Rhamno-Prunetea) (Arnáiz and Loidi 1983; Giménez de Azcárate et al. 1996; Costa et al. 2012).

Finally, one should mention the existence of pre-climax forest communities dominated by small evergreen trees (laurel, strawberry tree, holly). The dominant species include Laurus nobilis, Rhamnus alaternus, Arbutus unedo, Olea europea var. sylvestris, Phillyrea latifolia, Ph. angustifolia, Prunus lusitanica, etc., which occur scattered along those bioclimatic belts that are dominated by thermophilous deciduous forests (thermotemperate oak forests) and by xeric-evergreen woodlands (of cork oak or holm oak). Roughly ten associations have been described to include this type of formations, on siliceous as well as limestone soils, within the alliance Arbuto unedonis-Laurion nobilis (class Quercetea ilicis) (Bueno and Fernández-Prieto 1991; Aguiar and Capelo 1995; Loidi et al. 1997a; Costa et al. 2001; Rodríguez-Guitián et al. 2007; Pulgar and Manso 2010).

6.3.2 Edaphohygrophilous Forests

These are forests developed on soils that are saturated with moisture through most of the year. Their physiognomic and floristic features depend upon a large variety of environmental factors, such as air content in the soil, distance to river courses, or river turbulence regimes. Despite the fact that most of the catchments in this territory develop over small distances, as described above, they usually exhibit large variations in terms of flow, with maxima following the autumn rainfall and the snowmelt in spring, and relatively sharp low flows in summer, especially towards the west. This explains, together with the variety of thermotypes and bedrock types, the diversity of these forest types in the territory.

The distribution of these communities does not follow a simple pattern throughout the territory. In the eastern part of the Cantabrian Atlantic subprovince, the upstream segments (upper mesotemperate and supratemperate belts) of rivers draining into the Cantabrian Sea usually flow under a canopy of beech forests, which produce dense over-shading and prevent the formation of real riparian forests. Where the rivers leave the beech forests and enter the domain of the oak forests, their edges carry forests dominated by ash or alder (Hyperico androsaemi-Alnetum glutinosae). These forests occur almost continuously downstream until the river mouth (Amigo et al. 1987). The abundance of carbonated substrates favours the occurrence of many species of the order Fagetalia sylvaticae inside these forests, which are therefore included in the alliance Alnion incanae (class Salici purpureae-Populetea nigrae). Riparian communities dominated by large willows (Salix alba, Salix fragilis) (alliance Salicion albae, class Salici-Populetea) are only found on flood banks of the downstream segments of the largest rivers in this sector (Asón, Pas, Miera, Sella, Deva, Nalón, Narcea) (Díaz-González and Fernández-Prieto 1994; Loidi et al. 1997a).

In northwest Asturias and northern Galicia, the scarcity of beech forests allows a higher diversity of these riparian forests along stream banks. The upstream segments are occupied by woodlands dominated by hazel (Corylus avellana) and grey willow (Salix atrocinerea) (association Hyperico androsaemi-Coryletum avellanae). These are replaced downstream by ash forests with Fraxinus excelsior and Acer pseudoplatanus (association Valeriano pyrenaicae-Fraxinetum excelsioris) or by birch forests of Betula pubescens subsp. celtiberica with Corylus avellana and Frangula alnus (association Violo palustris-Betuletum pubescentis), and further downstream by silicicolous alder forests with ash (Fraxinus excelsior) of the association Valeriano pyrenaicae-Alnetum glutinosae (Amigo et al. 1987; Rodríguez-Guitián 2010; Díaz-González 2010a). All these communities are included in the alliance Alnion incanae.

The rivers of Galicia and Northern Portugal that drain into the Atlantic Ocean run through hilly landscapes that favour the development of silicicolous alder forests on river banks as from the upstream areas of their catchments (Senecioni bayonnensis-Alnetum glutinosae) (Amigo et al. 1987). In the mid and lower segments of the largest rivers (Minho, Lima, Douro) there are communities dominated by shrubby willows (Salix alba, Salix eleagnos subsp. angustifolia, Salix salviifolia, Salix neotricha) that develop along the alder forests and towards the riverbed on the pebble accumulations that are above the water surface during summer (alliance Salicion salviifoliae, class Salici-Populetea). In the mountains of Peneda and Gerês, stream banks are colonized by birch forests (Carici reuterianae-Betuletum celtibericae) (Honrado et al. 2003). This wide set of riparian forests hosts a number of endemic plant species (Omphalodes nitida, Narcissus cyclamineus, Senecio nemorensis subsp. bayonnensis) that are characteristic of the alliance Osmundo regalis-Alnion glutinosae, just as Fraxinus angustifolia among the tree species.

Finally, the segment of the river Ebro between Reinosa and Valle de Sedano (at the southern end of Cantabria), as well as its tributaries running through the Navarran-Alavese territory, host a peculiar set of woody riparian vegetation which includes alder forests of the association Humulo lupuli-Alnetum glutinosae (alliance Populion albae) on the river banks and willow scrub dominated by Salix neotricha (Salicetum neotrichae) (alliance Salicion discoloro-neotrichae) in the flood channel and on pebble islets that stay above the water level during summer (Biurrun 1999).

Altogether, riparian forests of the Cantabrian Atlantic subprovince are richest in species of vascular plants, especially in nemoral specialists. In addition to this remarkable floristic value most of the known Cantabrian Atlantic populations of several macaronesian ferns (Culcita macrocarpa, Dryopteris guanchica, Vandenboschia speciosa, Woodwardia radicans) and of the tertiary relict Prunus lusitanica are found in these forests, especially in their sheltered and hardly accessible segments.

Due to the abrupt topography of the majority of catchments in this territory, large alluvial flatlands submitted to seasonal flooding are scarce. Moreover, due to their high soil fertility and accessibility, these flatlands preserve only a very small fraction of their primeval forest cover, which has been replaced for centuries by croplands, and more recently by urban and industrial areas. The scarce data available from these forest types describe woodlands dominated by mixtures of oaks (Quercus robur, Q. pyrenaica), ashes (Fraxinus excelsior, F. angustifolia), alder (Alnus glutinosa), grey willow (Salix atrocinerea) and smooth-leaved elm (Ulmus minor), with abundant climbers and hygrophilous plants (Loidi et al. 1997a; Biurrun 1999; Amigo et al. 2009; Costa et al. 2012). The best representations of this group of forests are found in the Navarran-Alavese territory (associations Carici pendulae-Fraxinetum excelsioris and Viburno lantanae-Ulmetum minoris), in the Galician catchments of the rivers Miño and Sil (association Hedero hibernicae-Fraxinetum angustifoliae) and in northern Portugal (association Omphalodo nitidae-Fraxinetum angustifoliae). The first of these communities is included in the alliance Alnion incanae, whereas all the others belong to the alliance Populion albae (class Salici-Populetea).

The flatlands that are more prone to flooding promote the formation of marsh and mire environments, in the margins of which one can find forests that are developed on more or less acidic, highly organic substrates (alliance Alnion glutinosae, class Alnetea glutinosae). The situations where these forests are more frequent are located in the landward parts of estuaries, floodplains, and ancient meanders of the main rivers and lagoon systems on the coast and also inland on sedimentary environments. These forests are dominated by alder (Alnus glutinosa) with variable abundance of willow (Salix atrocinerea), thermophilous plants (Calystegia sepium, Laurus nobilis), large sedges (Carex paniculata subsp. lusitanica, Carex pendula) and ferns typical of these environments (Athyrium filix-femina, Dryopteris carthusiana, Osmunda regalis, Thelypteris palustris). The association Carici lusitanicae-Alnetum glutinosae is found from the Basque Country down to southern Galicia and northern Portugal, where it is gradually replaced toward the south by the association Carici lusitanicae-Salicetum atrocinereae. In some areas with a colder climate (e.g. in the mountains of northern Galicia), alder and many of the above-mentioned vascular plants disappear from these marsh forests, being replaced by birch (Betula pubescens subsp. celtiberica) and Myrica gale, with an herbaceous undergrowth of Deschampsia cespitosa subsp. subtriflora, Carex laevigata or Molinia caerulea and bryophytes of the genus Sphagnum at ground level (Izco et al. 2001b).

Edge communities of edaphohygrophilous forests differ depending on climate and topo-edaphic conditions. In the upstream areas, communities dominated by Erica arborea and Frangula alnus are common throughout all the Cantabrian Atlantic territories. Where rivers run through flatlands, thorn scrub usually develops, recognisable by the abundance of Prunus spinosa, Crataegus monogyna and Frangula alnus (class Rhamno-Prunetea). The association Rubo ulmifolii-Rosetum corymbiferae occurs at forest edges of floodplains in the Inner Galician territory (Giménez de Azcárate et al. 1996; Amigo et al. 2009). In the case of marsh and mire forest dominated by birch, their degradation is usually followed by the development of tall scrub with Myrica gale and heather species typical of damp soils (Erica mackaiana, Erica tetralix, Erica ciliaris) (Izco et al. 2001b).

6.4 Seral Scrub

The succession stages of different climax woodlands depend on the degree of disturbance that affects those formations. The regressive succession of the different broad-leaved woodlands can be synthesized considering two levels of disturbance in these forests: a moderate level at which most of the soil conditions are maintained and a severely degraded level wherein there is a loss of organic material from the top horizons, and nutrient depletion caused by erosion.

6.4.1 Shrubby Formations After Moderate Disturbance

Where there has been a total or partial deforestation in a woodland area but the soil characteristics have not been excessively deteriorated, the open spaces allow the development of thickets. These formations of small phanerophytes quickly become dense and will rapidly succeed in restoring the forest if the disturbance ceases to exist. These thickets of early-stage seral shrubs can be classified into two major types: prickly thickets on meso- to eutrophic soils that correspond to the Rhamno catharticae-Prunetea spinosae class and heliophytic thickets formed by retamoid shrubs of the Cytisetea scopario-striati class. Often the species that form these communities occur as isolated individuals within forests, as a result of clearings caused by falling trees or other occasional disturbances. They are more often displayed as woody fringes, creating a buffer zone between the forest and the other vegetation. They also appear as linear features outside the forest ecosystems, used by farmers to create boundaries between farmland and grassland where the livestock grazes.

Meso-eutrophic woodlands developed on base-rich soils originating from limestone have Rhamno catharticae-Prunetea spinosae thickets. In the Navarran-Alavese, Santanderian-Biscayan and Central-East Oviedo territories, those communities are dominated by thorny deciduous shrubs with seeds dispersed mainly by birds (Prunus spinosa, Cornus sanguinea, Ligustrum vulgare, Crataegus monogyna, Euonymus europaeus, Rosa sp. pl., etc.). The most common association is the Tamo communis-Rubetum ulmifolii which also reaches the North Galicia and Asturias and even the Galician and North Portugal sectors (Fig. 6.12). In the Navarran-Alavese area there is another association exclusively related to mesophytic oak woods, called Rhamno catharticae-Crataegetum laevigatae, with shrubs such as Rhamnus cathartica, Viburnum lantana or Crataegus laevigata. Both associations belong to the alliance Pruno spinosae-Rubion ulmifolii, occurring in thermotemperate and mesotemperate, but reaching even mesomediterranean thermotypes (Berastegi et al. 1997a; Loidi et al. 1997a). These formations, dominated by thorny shrubs, can sometimes reach the supratemperate belt, where they might include some characteristic species of the Rhamno alpini-Berberidion vulgaris alliance, such as Berberis vulgaris, Rhamnus cathartica or Rosa villosa, as has been reported from the Santanderian-Biscayan territory (Onaindía 1986). They can also form less dense thickets belonging to the Rhamno catharticae-Prunetea spinosae but with a low proportion of spiny shrubs, being part of the seral stages of oligotrophic temperate woodlands. Such formations are known from the Cantabrian and Basque to the Galician and North Portugal sectors and form the association Frangulo alni-Pyretum cordatae (Herrera et al. 1991). It is worth mentioning that often in the Galician and North Portugal sector, the Frangulo alni-Pyretum cordatae is replaced by similar communities dominated by brambles (Rubus spp.), and in the North Lusitania Sierran sector those communities are enriched by several endemic species of brambles in the mountain areas, such as Rubus vagabundus, Rubus lainzii, Rubus brigantinus and Rubus henriquesii.
Fig. 6.12

Thorny scrub (Tamo communis-Rubetum ulmifolii) on deep limestone soils used as boundary between pastures and arable lands. In the background, holm oak (Quercus rotundifolia) woodland on stony limestone soil. Becerreá Valley (Lugo, Galicia)

As part of the seral stages of acidophilous Quercus robur, Quercus pyrenaica or Fagus sylvatica woodlands, there are other types of thickets from Navarre to Portugal formed by retamoid species (non-leafy evergreen shrubs with flexible photosynthetic branches) such as Cytisus commutatus, Cytisus scoparius, Cytisus cantabricus, Cytisus grandiflorus, Adenocarpus lainzii, Genista florida subsp. polygaliphylla in communities that belong to the Cytisetea scopario-striati class; most of the broom species are non-leafy evergreen, an adaptation to exposed environments which allows controlling water loss by evapotranspiration. In the Cantabrian and Basque sector these broom formations belong to the Ulici europaei-Cytisetum commutati association, and in the Santanderian-Biscayan territory to the Cytiso scoparii-Genistetum polygaliphyllae. In the western areas of the North Galician-Asturian territory they are the most conspicuous and common type of heliophilous seral formations. There are several examples of communities dominated by different species of Cytisus: the Cytisetum striati, which is most widespread from the Central-East Oviedo area to the South Galician-Portuguese territories; the Ulici europaei-Cytisetum ingramii in the North Galician-Asturian territory; and even the Lavandulo sampaioanae-Cytisetum multiflori in the Inner Galicia territory with a mesomediterranean climate. In areas with less oceanic influence (again in the same Inner Galicia or North Lusitania Sierran sector) there are broom communities of the Cytiso striati-Genistetum polygaliphyllae association and in the lowland areas of the South Galician-Portuguese territory the Cytisetea communities can incorporate thermophilic Cytisus species such as Cytisus grandiflorus. In this Galician and North Portugal sector, on heavily mobilized anthrosols derived from granites, the Cytisus communities can be replaced by Adenocarpus lainzii, which appears to be more competitive there. The class Cytisetea scopario-striati also encompasses other communities which are not dominated by retamoid species but by white heather (Erica arborea), such as the Avenello flexuosae-Ericetum arboreae in hyperhumid areas, or the Genisto falcatae-Ericetum arboreae under temperate sub-Mediterranean climate. Those original tall heather formations are also present in the Cantabrian and Basque sector where the Pteridio aquilini-Ericetum arboreae is one of the successional stages of acidophilous Fagus-woodlands. By contrast, in the westernmost sectors the occurrence of thorny formations of the Pruno-Rubion ulmifolii is scarce and fragmented, which is consistent with the shortage of basic or ultrabasic substrates (Díaz-González and Fernández-Prieto 1994; Loidi et al. 1997a; Izco et al. 1999; Costa et al. 2000; Rodríguez-Guitián et al. 2003; Costa et al. 2004).

6.4.2 Shrubby Formations After Prolonged Disturbance

Anthropogenic pressure caused by the removal of large areas of forest and the prevention of progressive succession by fire and grazing leads to the formation of woody seral stages dominated by low shrubs, denoting a substantial change in soil quality: the upper organic horizons are lost by erosion and high rainfall causes the migration of nutrients to the lower layers, so that the soil will lose fertility and become more acid. This process has resulted in the proliferation of a peculiar type of scrublands throughout Atlantic Europe: heathlands. They are the result of man-vegetation interaction over the last 4000 years, which resulted not only in a particular and very recognizable type of plant communities, but also in similar forms of exploitation and management of the vegetation by repeated logging or burning (Diemont et al. 1996; Webb 1998).

These heathlands are named as such because of the abundance of different species of the heather family (Erica, Calluna, Daboecia). In the Cantabrian Atlantic territories these species co-dominate with species of thorny woody shrubs of the genus Ulex; depending on their respective dominance they are commonly called heath-gorse formations or just gorse formations (Fig. 6.13). These communities belong to the class Calluno vulgaris-Ulicetea minoris and achieve in this territory the highest richness of associations throughout Europe (Díaz-González 1998; Izco et al. 2007, Loidi et al. 2007, 2010). The diversification of the Calluno-Ulicetea class in our study area assumes the presence of two major alliances: heath-gorse formations under humid and hyperhumid ombrotypes, and dynamically related to oligotrophic forests, which is present throughout the territory, and belongs to the alliance Daboecion cantabricae; and another subhumid to humid acidophilous scrub, that is well adapted to the sub-Mediterranean climate of most of the Galician and North Portugal and North Lusitania Sierran sectors, and is classified as the Ericion umbellatae alliance. The dominant species of the Daboecion cantabricae are Daboecia cantabrica, Erica vagans, Ulex gallii subsp. breoganii, Erica mackaiana, Erica ciliaris and Thymelaea coridifolia. This alliance includes up to 18 different associations in the Cantabrian Atlantic area that result from different combinations of biogeographic units and a variation of ombrotypes, substrates, etc. In the Cantabrian and Basque and Central-East Oviedo territories, the Erico vagantis-Ulicetum europaei association is very common on decarbonated basic substrates. Also the Daboecio cantabricae-Ulicetum cantabricae is common, thriving best under colder conditions and reaching higher altitudes. In the North Galician-Asturian territory the endemic association Ulici breoganii-Ericetum mackaianae occurs, and in the Galician and North Portugal sector the association Ulici izcoi-Ericetum cinereae is very conspicuous in the landscape. In both territories the gorse may disappear with the decrease of oceanity, and is being replaced by communities dominated by heather and forming the Pterosparto cantabricae-Ericetum aragonensis association (a very abundant association in supratemperate territories of the Orocantabric subprovince), or the Carici asturicae-Ericetum aragonensis, typical of the Serra do Gerês in the North Lusitania Sierran sector (Díaz-González and Fernández-Prieto 1994; Herrera 1995; Loidi et al. 1997b; Izco et al. 1999; Honrado et al. 2004). (Figs. 6.14 and 6.15)
Fig. 6.13

Heath (Erica cinerea) and gorse (Ulex latebracteatus subsp. izcoi) as main floristic components of an acidophilous Cantabrian Atlantic seral scrub. Galician and North Portugal heathland (Ulici izcoi-Ericetum cinereae) at Bueu (Pontevedra, Galicia). (Photo by M.I. Romero-Buján)

Fig. 6.14

Hyperhumid heath-gorse community (Gentiano pneumonanthes-Ericetum mackaianae) on peaty soils in a supratemperate area of the northern Galician-Asturian mountains. Xistral Range (Lugo, Galicia)

Fig. 6.15

Flowering heathland colours: red (Erica australis subsp. aragonensis) and yellow (Pterospartum tridentatum subsp. cantabricum) at the Leboreiro Range (Galicia/Portugal). Heath communities like this occur widespread on granitic Inner Galician and North Lusitania Sierran territories

On the other hand, the alliance Ericion umbellatae comprises mainly associations present in the Mediterranean area of West Iberia with a humid ombrotype and penetrating into some temperate areas (sub-Mediterranean variant) of the northwest quadrant, particularly in the Galician and North Portugal and North Lusitania Sierran sectors. Their communities are characterized by the presence of Ulex minor, Ulex micranthus, Ulex latebracteatus, Pterospartum tridentatum subsp. lasianthum, Genista triacanthos, Cistus psilosepalus or Thymelaea broteriana. The Pterosparto lasianthi-Ericetum cinereae and Ulici micranthi-Pterospartetum lasianthi can be considered the most widespread associations within this biogeographic unit (Pulgar 1999; Honrado et al. 2004; Costa et al. 2008); in the South Galician-Portuguese territory the latter occurs with the endemic gorse Ulex micranthus and prickled broom (Pterospartum tridentatum s.l.) on schist substrates with an Atlantic influence, but on granites the Ulicetum latebracteato-minoris association dominates areas with an oceanic influence and is also dominated by an endemic gorse (Ulex latebracteatus).

Among the diversity of the Cantabrian Atlantic heath-gorse communities we must consider other associations specialized in highly selective ecological environments. This is the case with the weakly halophytic (splashed by marine salt spray) heath-gorse of the coastal cliffs that belongs to the alliance Dactylo maritimae-Ulicion maritimi; or the hydrophilic heathlands included in the Genistion micrantho-anglicae alliance. Both cases must be interpreted as permanent communities (permaseries) and not as seral heaths, and shall be addressed in Sect. 6.6.

In the eastern territories beyond Central-East Oviedo the dominance of calcareous substrates favours the presence of other shrubs that have a similar ecologic role as heathlands of the neutral-basophilic series. There is no strong acidification of the soil and loss of cations as in the case of the heathlands, but the loss of soil in the top layers by erosion can be similar. The presence of cushion chamaephytes gives a characteristic physiognomy to these scrub formations classified in the Festuco hystricis-Ononidetea striatae class. Two associations are recognized within this class, both dominated by a shrubby, cushion-shaped legume, Genista hispanica subsp. occidentalis: in the East Basque and Navarran-Alavese territories these spiny formations, belonging to the Helictotricho cantabrici-Genistetum occidentalis association, can be considered a successional stage towards mesotrophic Fagus sylvatica and Quercus robur woodlands in both sectors, or of the holm oak woodlands (dominated by the evergreen Quercus ilex) in the Cantabrian and Basque sector. In the Central-East Oviedo area and Santanderian-Biscayan territories these spiny formations have gorse (Ulex europaeus) in their composition, forming the Ulici europaei-Genistetum occidentalis association. Both associations are belong to the alliance Genistion occidentalis (Díaz-González and Fernández-Prieto 1994; Loidi et al. 1997a; Loidi and Báscones 2006).

Besides those communities widely distributed in the temperate Cantabrian Atlantic territories (thorny scrub, broom formations and heathlands), we should mention the singular and sporadic presence of acidophilous shrubs dominated by rock-roses (Cistus sp. pl.); they are the ecological vicariant of heathlands in the Mediterranean territory, with subhumid to semi-arid ombrotypes. These communities are concentrated in the Galician-Portuguese mesomediterranean part and the subhumid part of the Sil river valley, with evergreen forests as potential vegetation (Quercus rotundifolia, Quercus suber), although its extension in terms of area does not exceed 300 km2. They are dominated by Cistus ladanifer or Cistus populifolius and there are at least two associations within the alliance Ulici argentei-Cistion ladaniferi of the typical Mediterranean class Cisto-Lavanduletea stoechadis (Izco and Ortiz 1985).

There are other examples of shrub communities dominated by species of undeniable Mediterranean character that can be found from the Basque Country to Portugal, as seral stages of xero-thermophilic forest formations (acidophilous Quercus pyrenaica, and Quercus suber, and calcareous Quercus ilex woodlands) or as permanent communities on rocky outcrops of various kinds. Those are recognized by the dominance of Arbutus unedo, or sometimes by Phillyrea latifolia, and form a group of Cantabrian Atlantic associations that fall in the Arbuto unedonis-Laurion nobilis alliance of the Quercetea ilicis class (Díaz-González and Fernández-Prieto 1994; Loidi et al. 1994).

6.5 Herbaceous Vegetation

The abundance of precipitation and generally mild temperatures that characterize the Cantabrian Atlantic territory are especially favourable for the development of perennial herbaceous plant communities. However, on the long term vegetation dominated by herbaceous plants is less competitive than woody vegetation, so the presence of herbaceous communities at a particular location corresponds to one of the following circumstances: it can be a seral stage resulting from the removal of forest or shrub cover and will eventually be replaced by those types of vegetation, except in the case of secondary succession that is blocked by anthropic pressure, or it is a permanent community that represents the most stable situation in a specific biotope subject to very limiting ecological factors (pioneer communities on soils in their early stages of formation, mountain tops affected by wind and cryoturbation, permanently flooded areas, cracks in rock walls with little weathering, etc.). Some of this vegetation is associated with stressful environments such as sand dunes, coastal salty habitats, or peatlands. This will be discussed in a later Sect. 6.6. In this section we will address grasslands communities that are very noticeable in the landscape because their maintenance is associated with agricultural and pastoral practices. We shall also describe some of the rupicolous communities in the end.

6.5.1 Semi-natural Managed Grasslands

Perennial grasslands periodically mown to provide hay for livestock are one of the most characteristic elements of the Cantabrian Atlantic landscape. The diversity of grasslands results from the different lithological conditions from which the soil is derived. Topographic variability (in valleys but also on steep slopes) and the water regime of the soils (natural or managed) also contribute to shape this variety. These factors influence the type of existing herbaceous vegetation more profoundly than biogeographic and bioclimatic conditions affecting the flora of such habitats. Additionally, we should consider the intensity of man’s management practices such as mowing, planting, adding depleted nutrients, selecting the type of livestock that grazes those grasslands, etc.; all of those contribute to the variety in semi-natural grassland communities comprised within the Molinio caeruleae-Arrhenatheretea elatioris class.

Throughout the entire Cantabrian Atlantic area hay meadows have been described from non-hydromorphic soils, with periodical hay cutting and in some cases with subsequent manuring, which are part of farming practices undertaken for centuries (Tüxen and Oberdorfer 1958; Rivas Goday and Rivas-Martínez 1963; Braun-Blanquet 1967; Bellot 1968; Teles 1970; Díaz-González and Fernández-Prieto 1994; Berastegi 2013). Examples are the meadows belonging to the Arrhenatherion elatioris alliance: those of the Malvo moschatae-Arrhenatheretum elatioris association, existing all over the Cantabrian and Basque and North Galicia and Asturias sectors, can be considered as meadows with a relatively great diversity of herbaceous species per unit area (Izco and Guitián 1984). The North Galician-Asturian territory, and especially the Galician and North Portugal and North Lusitania Sierran sectors, harbours another association, the Agrostio castellanae-Arrhenatheretum elatioris, which is somewhat less rich in species but it behaves like the vicarious version of the previous association in the occidental Cantabrian Atlantic (Teles 1970); for their persistence in the North Lusitania Sierran sector (where the sub-Mediterranean climatic influence is more pronounced) these managed grasslands are irrigated by very small canals during part of the year and are never grazed during winter.

Other semi-hygrophilous grasslands, resulting from a combined management of mowing and grazing by cattle, are found throughout the territory, and are included within the alliance Cynosurion cristati. They are usually less diverse in species richness than the previous alliance and show a greater dominance of grass species. This alliance contains at least four associations: the Lino biennis-Cynosuretum cristati on deep soils in the thermotemperate and mesotemperate thermotypes from Navarre to Galicia; the Merendero pyrenaicae-Cynosuretum cristati in the Cantabrian and Basque and North Galicia and Asturias sectors but in the supratemperate thermotype; the Caro verticillati-Cynosuretum cristati also in the thermo/mesotemperate thermotype but on oligotrophic soils of the North Galician-Asturian territory and Galician and North Portugal sector; and the Anthemido nobilis-Cynosuretum cristati in meso/supratemperate thermotypes in the North Lusitania Sierran sector and South Galician-Portuguese territory (Bellot and Casaseca 1956; Tüxen and Oberdorfer 1958; Teles 1970). (Figs. 6.16 and 6.17)
Fig. 6.16

Hay meadows (Molinio-Arrhenatheretea) were a common element of the Cantabrian Atlantic landscape since the Middle Ages, but nowadays their extension and use have been reduced considerably. Cynosurion cristati meadow at late spring time in Friol (Lugo, Galicia) (Photo by M.I. Romero-Buján)

Fig. 6.17

Mown meadows (Lino biennis-Cynosuretum cristati) at different stages of hay collection at Abadín (Lugo, Galicia)

Since the middle of last century it has been found that the abandonment of traditional forms of management in the grasslands of the Arrhenatherion elatioris has led to their transformation into Cynosurion cristati pastures. This transformation has affected more strongly the territories with basic-neutral soils, where Arrhenatherion elatioris meadows were more common, such as in the Cantabrian and Basque sector and the Central-East Oviedo territory. In the South Galician-Portuguese territory and in the North Lusitania Sierran sector there were recent changes in landscape management and most of the Cynosurion cristati meadows have disappeared due to the abandonment of the practice of closing off the pastures before spring begins, following the cattle grazing season in winter.

6.5.2 Poorly Managed Wet Meadows

The presence of hygrophilous meadows, in many cases exploited for hay, is common throughout the territory. These grasslands are located in areas of high rainfall, little or no summer drought and gentle topography, conditions involving a prolonged waterlogging of the soils. The floristic composition of these meadows shows a relatively high frequency and even dominance of species of the genera Juncus and Carex, grasses (Deschampsia, Molinia) and other hygrophilous and meso-hygrophilous forbs. Up to six different thermo/meso/supratemperate associations of oligotrophic grasslands belonging to the alliance Juncion acutiflori have been described. But in the Cantabrian and Basque sector and Central-East Oviedo territory there are also examples of hygrophilous grasslands on base-rich neutral soils, belonging to the alliance Molinion caeruleae, and even Calthion palustris, which are indicators of a lesser degree of oceanity.

Among the wide variety of hygrophilous meadows in our territory there are dense grasslands of tall sedges and rushes (Schoenus nigricans, Scirpoides holoschoenus or Juncus acutus) developed on soils with marked temporal hydromorphism, typical of the alliance Molinio caeruleae-Holoschoenion vulgaris. Although this alliance mainly occurs in the Mediterranean region, it may be present in several sectors along the Cantabrian Atlantic subprovince at particular sites with heavy clay soils, and in coastal dune slacks.

6.5.3 Other Grasslands

The pastures addressed so far, despite their response to certain habitat conditions, have been maintened over time due to human activities which mainly focused on the harvest and use of biomass to sustain livestock combined with possible direct grazing. But throughout the territory we find other communities, belonging to the same class Molinio-Arrhenatheretea, that respond to conditions of increased supply of nutrients such as nitrogen or phosphorus, combined with trampling as a result of greater grazing pressure (Loidi et al. 1997a; Biurrun 1999; Honrado 2003; Berastegi 2013). The floristic differences produced in grasslands under such conditions have given rise to other community types:
  • From the entire Cantabrian Atlantic subprovince some grasslands of the Lolio perennis-Plantaginion majoris have been described. They formed under strong trampling conditions that led to soil compaction and nitrification by cattle, and that resulted in an increase of rosette hemicryptophytes (Plantago sp. pl., Hypochaeris radicata, Bellis perennis, Chamaemelum nobile, etc.).

  • Potentillion anserinae communities are known from the East Basque to the South Galician-Portuguese territories. They occur as nitrified hygrophilous meadows, and are often rich in rushes that colonize river channels that are subject to regular flooding which results in sediment deposition.

  • There are also perennial grasslands on loamy nitrified soils, belonging to the alliance Paspalo distichi-Polypogonion viridis. Although these communities are more common in the Mediterranean region, in the Cantabrian Atlantic territory they have been reported from estuaries with regular tidal debris deposition.

  • Occurring in small areas in the territory, but with a very distinct physiognomy, are Trifolio fragiferi-Cynodontion dactyli pastures, grassland communities dominated by Cynodon dactylon. Although the optimum bioclimate of these communities is Mediterranean, they appear rather frequently on compacted sandy soils with temporal hydromorphy, such as stabilized dune systems and areas close to the coast, predominantly in the thermotemperate belt.

  • Even though dry grasslands are very common in Mediterranean territories, several associations can be found in sub-Mediterranean climates. Most of these communities belong to the class Stipo giganteae-Agrostietea castellanae, and incorporate associations typical of deep soils, while others can occur on shallow soils or outcrops. Several grassland communities occurring on deep soils are dominated by Agrostis castellana, and belong phytosociologically to the Agrostion castellanae alliance. They can be found in the South Galician-Portuguese territory.

6.5.4 Calcareous Meso/Xerophytic Grasslands

The grassland communities referred to above generally thrive on moist, deep soils, sometimes even temporary waterlogged. But there are also many natural mesophytic or xerophytic grasslands with dense swards, occurring on soils without temporal hydromorphy. They belong to the Festuco valesiacae-Brometea erecti class and are abundant in subsectors dominated by calcareous substrates (Central-East Oviedo territory and Cantabrian and Basque sector), occurring sporadically in western subsectors. Although such grasslands belonging to various associations are known from the neighboring Pyrenean and Orocantabrian subprovinces, in the Cantabrian Atlantic territory two main associations occur: the most widely represented is the Seselio cantabrici-Brachypodietum rupestris, usually characterized by the dominance of Brachypodium pinnatum subsp. rupestre; and on loamy soils in the Navarran-Alavese territory the Calamintho acini-Seselietum montani association is found (Loidi et al. 1997a; Berastegi 2013). Both associations belong to the alliance Potentillo montanae-Brachypodion rupestris. (Fig. 6.18)
Fig. 6.18

Calcareous grassland (Calamintho-Seselietum montani) in the foreground; along with hay meadows (Cynosurion cristati, in the background) they have been the traditional way of human exploitation of the potential area of mesophilous and calciphilous Navarran-Alavese oak woodlands (Roso-Quercetum pubescentis and Crataego-Quercetum roboris). Arbizu, Urbasa-Andía Range (Navarra) (Photo by Monika Janišová)

In the Cantabrian and Basque territory dry, calcareous grassland communities also occur. Their typical floristic composition consists of a mixture of caespitose hemicryptophytes and dwarf chamaephytes that are adapted to environments subjected to cryoturbation on high mountain tops. These formations belong to the Festuco hystricis-Ononidetea striatae class, often characterized by the abundance of endemic species. In the Cantabrian and Basque sector they occur in at least two associations in the thermo and mesotemperate belts. Another association within this class, the Helictotricho cantabricae-Seslerietum hispanicae, is not linked to cryoturbation but occurs on slopes and rocky surfaces with large crevices and shallow soils. And in the supratemperate belt the association Carici ornithopodae-Teucrietum pyrenaici, adapted to mountain ridges with heavy snowfall, occurs (Loidi 1983; Loidi et al. 1997a).

6.5.5 Hygrophilous Caespitose Acidophilous Grasslands

We now address other communities of dense but low-growing grasslands, typical of acid soils in areas that remain cool in summer. They are included in the Nardetea strictae class and grow on both siliceous and calcareous substrates, but in the latter case only if rainfall is so intense that the cations are leached to deeper soil levels. Such grasslands have a high regional diversity dependent on several factors, such as altitude, radiation, and soil composition. Although the greatest diversity of grasslands of the Nardetea strictae class in the Iberian Peninsula is found in the orotemperate and oromediterranean areas of all mountain ranges, in the Cantabrian Atlantic areas they are quite frequent at meso- and supratemperate levels, which have high rainfall values. Up to six associations have been described from the four sectors of the territory concerned here (three Cantabrian Atlantic sectors plus North Lusitania Sierran), all belonging to the alliance Violion caninae (Darquistade et al. 2004; Izco et al. 2009). They are characterized by an abundance of grass or graminoid species, including Nardus stricta, Danthonia decumbens, Agrostis curtisii, Agrostis hesperica, Carex binervis, Carex pilulifera and Juncus squarrosus, and are accompanied by small forbs such as Potentilla sterilis, Pedicularis sylvatica, Galium saxatile, Carum verticillatum, Serratula tinctoria subsp. seoanei and Gentiana pneumonanthe.

6.5.6 Rupicolous Vegetation

This type of vegetation does not strictly consist of herbaceous plants, but also contains dwarf chamaephytes, some of which especially grow in small cracks and crevices. The endemic component of the flora typical of these habitats is very significant. Much of the rupicolous vegetation belongs phytosociologically to the class Asplenietea trichomanis. Within the Cantabrian Atlantic territories calcareous rocks have bigger dimensions in both length and height, than those of the siliceous type, and thus are more favourable for the development of communities that colonize crevices. Therefore, the Central-East Oviedo territory and the Cantabrian and Basque sector are the main areas with a great variety of communities in this category (Rivas-Martínez et al. 1984; Díaz-González and Fernández-Prieto 1994; Loidi et al. 1997a).

In the granitic outcrops of the Serra do Gerês (North Lusitania Sierran sector) the association Phalacrocarpo oppositifoliae-Silenetum acutifoliae appears in the supratemperate belt under sub-Mediterranean climate; within the humid ombrotype and extending from thermotemperate to mesomediterranean the association Linario glabrescentis-Cheilanthetum tinaei occurs. These silicicolous associations are classified in the Saxifragion willkommianae and Cheilanthion hispanicae alliances, respectively. These two alliances have a distinct Iberian Mediterranean distribution, but are represented in sub-Mediterranean territory in specific areas of the Galician and North Portugal and North Lusitania Sierran sectors, in xeric biotopes (Fernández-Areces et al. 1987; Honrado et al. 2012).

The calcicolous communities are much more adapted to humid and hyperhumid ombrotypes. In the Navarran-Alavese territory an association, the Violo biflorae-Saxifragetum paucicrenatae occurs. It belongs to an alliance (Violo biflorae-Cystopteridion alpinae) typical of cracks in the humid orotemperate ombrotypes with prolonged snow cover in Pyrenean and Orocantabrian territories. But the most diversified alliance is the Saxifragion trifurcato-canaliculatae, endemic to the South European Atlantic territory (sensu Rivas-Martínez et al. 2014) and represented by up to five associations: the Centrantho lecoqii-Phagnaletum sordidae is located in the mesotemperate part of the Santanderian-Biscayan territory, while the Dethawio tenuifoliae-Potentilletum alchimilloidis and Drabo dedeanae-Saxifragetum trifurcatae have supratemperate distributions throughout the Cantabrian and Basque sector (Loidi et al. 1997a). Finally, there are two associations that are best represented in Orocantabrian subprovince, but occur here and there also in the Central-East Oviedo territory: the Crepido asturicae-Campanuletum legionensis and the Saxifragetum paniculato-trifurcatae; both include specialists plants of vertical limestone walls, namely Saxifraga trifurcata, Crepis albida subsp. asturica, Campanula arvatica, Agrostis schleicheri and Antirrhinum braun-blanqueti.

The Petrocoptidetum glaucifoliae association can be found in the Central-East Oviedo territory as well, although its optimum is Orocantabrian, and it encompasses calcicolous rupicolous communities growing on calcareous vertical walls many times exceeding 90 degrees; this habitat of overhang limestone crags (balmes in Spanish) is more restrictive than the previous, and provides a refuge for highly specialized communities included in a different class: the Petrocoptido pyrenaicae-Sarcocapnetea enneaphyllae (Rivas-Martínez et al. 2002).

6.6 Littoral Zone and Peatlands

Considering the geomorphological and climatic characteristics of this geographical territory, there are two major types of azonal vegetation that are particularly remarkable in terms of presence in the various coastal landscape types, each of them with its own characteristic floristic and phytocoenotical diversity: coastal vegetation in all its forms and peatland environments.

6.6.1 Coastline: Three Kinds of Habitats Present

The length of the Cantabrian Atlantic coast is over 2500 km long and consists of a succession of three major ecological environments with different balances of erosion/sedimentation: the cliffs, sand beaches and saltmarshes. Each of these three environments offers ideal conditions for highly specialized types of vegetation: the halochasmophytic vegetation on the cliffs and rocky shores, the psammophilous vegetation on sandy coasts, and halophytic vegetation in river estuaries and other areas with brackish water. On all these environments there are quite a few studies about their vegetation types (Loriente 1974; Fernández-Prieto and Loidi 1984; Izco et al. 1993a, 2001a; Díaz-González and Fernández-Prieto 1994; Izco and Sánchez 1996; Bueno 1997; Loidi et al. 1997a; Costa et al. 1998b; Neto et al. 2007; Díaz-González 2009).

6.6.1.1 Rocky Shores

On rocky shores the processes of marine abrasion or deposition of large boulders are the dominant ones. Although the Cantabrian Atlantic rocky shores are formed by various lithological materials whose resistance to erosion is variable, the appearance of the vegetation that colonizes the cliffs is mainly due the dynamics of waves, usually stronger during the winter, and the salty spray splash. Both factors combined make a series of vegetation zones that indicate different levels of exposure to the mechanical action of waves and wind force charged with salts. There is a first line of discontinuous vegetation consisting mainly of chasmophytic hemicryptophytes and some succulent or suffruticose plants; various species of the Plumbaginaceae are part of those communities (genera Armeria and Limonium) some of them endemic to the territory. At least five different associations were recognized from northern Portugal to the Basque coast, all belonging to the alliance Crithmo maritimi-Armerion maritimae (Crithmo maritimi-Limonietea class). A second strip on the cliffs, that is safe from the mechanical action of waves, allows the establishment of a soil layer that can accommodate a dense graminoid cover, despite the salt spray. These grasslands are often dominated by the grass Festuca pruinosa, and are described in 4 different associations that are classified in the same phytosociological alliance referred to earlier (Fig. 6.19). Finally, at the top of the cliffs, where the rock weathering is more advanced, a type of shrubland, formed by cushion chamaephytes and dominated by gorse (Ulex sp. pl.) and heather (Erica sp. pl.) is present, being included in the Calluno vulgaris-Ulicetea minoris class (see Sect. 6.4). The presence in those communities of a unique set of genotypes and endemic species, adapted to aerohaline environments (Rumex acetosa subsp. biformis, Angelica pachycarpa, Daucus carota subsp. gummifer, Leucanthemum crassifolium), reveals that they are not part of seral shrub formations but are permanent communities (permaseries). This set of peculiar plants justifies their inclusion in a distinctive alliance, which also comprises five different associations ranging from the Cisto salviifolii-Ulicetum humilis in the Galician and North Portugal sector to the Ulici humilis-Ericetum vagantis in the Cantabrian and Basque one. (Fig. 6.20)
Fig. 6.19

Halophytic plant communities of Cantabrian cliffs (Crithmo maritimi-Armerion maritimae) include small cushion-shaped chamaephytes and dense grassland dominated by Festuca pruinosa. Both communities at Cabo Peñas (Asturias)

Fig. 6.20

Heather-gorse scrub, hemisphaerically shaped by marine wind (Dactylo maritimae-Ulicion maritimi). Cisto salviifolii-Ulicetum humilis at Cabo Vilán (A Coruña, Galicia) (Photo by M.I. Romero-Buján)

6.6.1.2 Sandy Shores

In the coastal sections where the deposition of coarse to medium-sized materials is predominant (pebbles or sand), sandy beaches are built. Here, the wind often carries sand particles inland, which form a dune system when they encounter an obstacle. These environments are well known for their difficulty in terms of colonization by plants, since to the selective factors already mentioned (waves, salt spray and sand burial caused by the wind) we must add an unstable and very low water holding capacity of the substrate. A distinct group of habitats are recognized universally in these dune systems dividing them into vegetation belts parallel to the tide line depending on wind action and the distance to the sea: embryonic dune, moving dune (or front dune) and fixed dune (or grey dune), with the possibility of having a fossilized dune further inland (brown dune). With the exception of fossil dunes, which can support a higher biomass and woody vegetation, the various communities that colonize the dune strips are highly specialized and integrated into the Euphorbio paraliae-Ammophiletea australis class. The embryonic dune corresponds to a single graminoid community with discontinuous coverage along the entire coast: the Euphorbio paraliae-Elytrigietum boreo-atlanticae. Behind this community, a distinct frontal dune stands out conspicuously, formed by the perennial grass Ammophila arenaria subsp. australis. This plant has a notable root system that possesses vertical rhizomes and can resist sand mobility and consequent burial. Also in this case the association that is recognized is the same for all Iberian Cantabrian Atlantic beaches: the Otantho maritimi-Ammophiletum australis. Finally, in the space behind the front dune, in which the decrease of the selective stress caused by wind allows the establishment of an environment with a greater plant diversity (grey dune), the communities are dominated by hemicryptophytes and chamaephytes. In the grey dunes of the Galician and North Portugal sector grow communities of the Helichrysion picardii alliance with suffruticose Iberian endemics of western Mediterranean origin (Iberis procumbens, Helichrysum picardii, Artemisia crithmifolia, Scrophularia frutescens, Alyssum gallaecicum); however, from the North Galician-Asturian territory to the Cantabrian and Basque sector, the vegetation of these grey dunes is somewhat poorer, and is placed in the alliance Euphorbio portlandicae-Helichrysion maritimi.

6.6.1.3 Salt Marshes

These are low muddy areas with a predominance of sedimentation of fine particles (silt and clay) carried by slow-flowing river water. They are much less exposed to wind and salt spray in comparison with the two previous cases, and are daily flooded by brackish water, mostly associated with rivers estuaries, with acid sulfate soils. Where the tide rises and falls they are usually traversed by numerous channels. The continuous mixing in different proportions of freshwater and saltwater, with daily and seasonal variations and various degrees of oxygenation of the soil, are the key factors that influence the distribution of plant communities in these environments.

There are several detailed studies on the diversity of plant communities in a great number of Cantabrian Atlantic saltmarshes (Izco et al. 1993b; Herrera 1995; Izco and Sánchez 1996; Bueno 1997). A simplified model should distinguish at least two different ecological positions:
  • An external halophytic saltmarsh subjected to a greater influx of salt water that floods the vegetation twice a day. Following a high to low tidal flooding gradient, we can distinguish this sequence of communities: the Zosteretum noltii submerged beds, grass formations of the Spartinetum maritimae, succulent chamaephytes communities of the Puccinelio maritimae-Sarcocornietum perennis and, in less flooded zones, the Halimionetum portulacoidis shrubland. All these associations are present from the Basque Coast to Portugal. Where the influence of flooding becomes smaller, the phytocoenotical biodiversity can increase because of the presence of succulent therophytic communities that normally occupy small areas, such as the Salicornietum fragilis or Salicornietum dolichostachyae. (Fig. 6.21)
    Fig. 6.21

    Saltmarshes at Corrubedo Natural Park (A Coruña, Galicia) showing dominant chamaephytes such as Halimione portulacoides and Sarcocornia perennis

  • An internal sub-halophytic saltmarsh, where the river inputs are predominating compared with seawater entry, and thus less salty water (brackish). These environments are common in all estuaries, often dominated by rush beds such as the Junco maritimi-Caricetum extensae or Agrostio stoloniferae-Juncetum maritimi or reeds/tall sedges communities of the Armerion maritimae alliance. Communities with much lower biomass can also occur in those mosaics, such as the Enteromorpho intestinalidis-Ruppietum maritimae present in channels and small ponds with slow water evaporation, or the four associations of the alliance Limonio ovalifolii-Frankenion laevis, which occur on sandy soils that drain easily at low tide.

6.6.2 Peatlands

The warm and humid climate that characterized the Cantabrian Atlantic territories throughout the Holocene has favoured the formation of a large number of peat wetlands. The variety of geomorphological environments that currently characterizes these ecosystems can be summarized as: blanket bogs, slope raised bogs, large depressions and valley peatlands and corrie bogs.

The variety of climatic and pedo-topographical conditions where these wetlands appear influences their extent, complexity and number of ecological environments represented (bogs, swamp forests, wet heaths and grasslands, communities of clear running waters, ponds, lagoons, etc.). Presently, the Cantabrian Atlantic territory of Galicia and the west part of Asturias are the areas with the greatest number and diversity of peaty areas in the Iberian Peninsula (Ramil-Rego et al. 1996; Izco et al. 2001b).

Traditionally the vegetation of the peat areas has been divided into two types of vegetation classes based on floristic criteria and degree of mineralization of the water that goes through these systems: the Oxycocco palustris-Sphagnetea magellanici (very acidic bog vegetation, with or without tall hummocks) and the Scheuchzerio palustris-Caricetea nigrae (peatland vegetation from acidic to basic substrates, with generally a flat topography). However, there are intermediate situations in which the inclusion in one of the two classes mentioned is difficult from a phytosociological point of view. When peat systems cover large areas they often form complex mosaics with other vegetation types (classes Alnetea glutinosae, Molinio-Arrhenatheretea, Littorelletea uniflorae, Calluno-Ulicetea, Montio fontanae-Cardaminetea amarae) whose diversification and local distribution is strongly influenced by various environmental factors (Moore 1968; Ellenberg 1988; Rivas-Martínez 2011; Costa et al. 2012).

6.6.2.1 Blanket Bogs

These bogs develop under very particular conditions: mountain tops of flat topography or with gentle slopes, on nutrient-poor rocks (quartzites, sandstones, granitic rocks) and subjected to a strong oceanic climate (hyperoceanic). Although in the early Holocene this type of wetland covered large areas of the Cantabrian Atlantic mountains, subsequent vegetation dynamics and human disturbance caused their disappearance or colonization by other vegetation (forests, wet heaths and grasslands, forest plantations). Today the Iberian active blanket bogs cover a few mountain ranges of northern Galicia (Xistral and Capelada mountain range, Montes do Buio) where they occupy a restricted area of about 2700 hectares (Izco et al. 2001b; Rodríguez-Guitián et al. 2009), and small pockets in some central-eastern mountain ranges such as the Monte Zalama from the Santanderian-Biscayan territory (Heras and Infante 2004). These active blanket bogs are the most southwestern ones on the European mainland, sustaining endemic vegetation types and containing valuable paleobotanic information concerning the environmental changes that occurred in the territory during the past 10,000 years (Ramil-Rego 1992; Muñoz Sobrino et al. 2005).

The Galician blanket bog vegetation develops over peat deposits that are generally 0.5 to 5.0 m thick (Izco et al. 2001b); the vegetation is mainly composed of Eriophorum angustifolium, Carex durieui, Molinia caerulea, Avenella flexuosa, Trichophorum cespitosum, etc., evidencing the limited role of bryophytes and heather (Erica mackaiana, Calluna vulgaris) unlike other types of blanket bog in western Europe (Fig. 6.22). The communities described in Galicia are assigned to the endemic Iberian alliance Erico mackaianae-Sphagnion papillosi (Rodríguez-Guitián et al. 2009). At Mount Zalama the active part of the blanket bog is covered by a floristically singular herbaceous-woody vegetation dominated by Calluna vulgaris, Erica tetralix, Eriophorum vaginatum, Molinia caerulea, Daboecia cantabrica, Hypnum cupressiforme and Dicranum scoparium (Heras and Infante 2004).
Fig. 6.22

Summertime appearance of NW Iberian active blanket-bog communities (Carici durieui-Eriophoretum angustifolii, Molinio caeruleae-Eriophoretum angustifolii) at the top of the Xistral Range (Lugo, Galicia)

6.6.2.2 Slope Peatlands

These are wetlands of small size but relatively frequent in the territory, particularly in the central-western Cantabrian Atlantic territories. Usually they form on the lower and middle slopes as a result of resurgences of subsurface waters, which favour peat formation processes, whose activity is maintained as long as there is a supply of water from the springs. Where the water is low in nutrients these wetlands usually consist of small ponds in their upper parts, feeding down-slope Sphagnum-rich raised bogs belonging to the alliances Ericion tetralicis and Erico mackaianae-Sphagnion papillosi (Figs. 6.23 and 6.24). There are variations of these acidic peaty systems that develop into forested peatlands dominated by Betula pubescens subsp. celtiberica, accompanied by Salix atrocinerea, Frangula alnus and Myrica gale in the North Galician-Asturian territory (Izco et al. 2001b) and by Osmunda regalis in the East Basque territory (Peralta et al. 2013).
Fig. 6.23

Different types of peatlands favour different plant communities. Sphagnum-rich cushion-shaped peatlands (Erico mackaianae-Sphagnion papillosi) at the Xistral Range (Lugo, Galicia) (Photo by M.I. Romero-Buján)

Fig. 6.24

Acidic valley bottom complex mire dominated by cotton sedge (Eriophorum angustifolium). Abadín (Lugo, Galicia) (Photo by M.I. Romero-Buján)

Herbaceous formations dominated by bryophytes appear in areas with gentle slopes with an abundant supply of mineral-rich water (Eucladium spp., Cratoneurion spp.), belonging to the alliance Cratoneurion commutati (class Montio-Cardaminetea). In permanent waterlogged areas with high ions concentrations, alkaline fens occur with Schoenus nigricans, Carex davalliana, etc. (alliance Caricion davallianae, class Scheuchzerio-Caricetea nigrae). When the water resurges on slopes of strong inclination or rocky walls, communities composed by brown mosses and ferns occur, being assigned to the alliance Adiantion capilli-veneris (class Adiantetea capilli-veneris) and characterized by the formation of carbonate precipitates (tufa or travertine).

6.6.2.3 Sedimentary Depressions and Valley Bogs

These wetlands are mainly associated with areas affected by regular fluctuations in their water tables as a result of changes in the flow of adjacent rivers. They typically cover large areas, although many of them have been transformed for centuries in areas of agricultural use or for livestock grazing by opening drainage channels. In the best preserved areas the majority of communities in these peat systems are similar to those described for mountain peatlands with the prominence of certain vegetation types linked to drainage channels (Eleocharition multicaulis), ponds and small lakes (Littorellion uniflorae, Utricularion vulgaris), and megaforbic communities (Filipendulion ulmariae, Magnocaricion elatae) together with bog woodlands (class Alnetea glutinosae).

6.6.2.4 Corrie Bogs

Corries (or tarns) are small pools placed in depressions originating from glacial plucking. This type of environment is relatively scarce in the Cantabrian Atlantic mountain ranges, especially when compared with the neighboring Orocantabrian subprovince. The best examples are found in the mountains of the North Lusitania Sierran sector as well as in the mountains along the boundary between Cantabria, Burgos and the Basque Country, although many of them have been much altered since antiquity, because of summer grazing by cattle. The corries are usually found in different stages of sedimentation; some of them may become dry during the summer, but others remain with open water throughout the year, with oligotrophic, floating communities (alliance Caricion nigrae) or transitional acid bogs with Sphagnum hummocks (alliance Ericion tetralicis) at their edges.

6.7 Vegetation Series

The idea of vegetation series originated from the notions proposed by Clements (1916), when exposing all the explanatory conceptual contributions regarding the replacement of plant communities in the same physical space in what is known as vegetation dynamism. More recently, as a result of the great development of Phytosociology as a method of analysis of vegetation, a precise definition was established: “A Vegetation Series or Sigmetum is a geobotanic notion that tries to express all the plant communities, or collection of stages, that can be found in similar tessellar places as a result of the succession processes” (Rivas-Martínez 2002b). This definition is based on the concept of “tessella”, a geographical territory of greater or lesser extent, environmentally homogenous, with one association as potential climax vegetation and therefore a certain sequence of communities of substitution (Rivas-Martínez 2005). The vegetation series (or sigmetum), besides being the basic unit of Dynamic Phytosociology, is an especially useful tool for mapping the natural environment and for interpreting landscape dynamics in areas, such as described here, where the interaction of human populations with their environment has been intense since prehistoric times.

In general the mature stage in ecological succession, also known as climax, is represented by a woodland association. Those are the vegetation types with more biomass and greater structural complexity towards which, over time, all seral communities of each tesela in a progressive succession evolve, in the absence of disturbances. Most of the vegetation series are named after the mature stage woodland association, which represents the Potential Natural Vegetation (PNV) for each particular series, commonly referred to as Cabeza de Serie in Spanish geobotanical literature.

Based on the response of the vegetation series to the environmental conditions provided by the territory’s macroclimate, or if the territory is submitted or conditioned by excess or shortage in terms of water availability (due to topography, a special geological substrate, proximity to watercourses, etc.), we can distinguish four different types of series (Loidi et al. 2011):
  • Climatophilous: series on mature soils with water intake only from rain.

  • Temporihygrophilous: edaphophilous series on wet soils but only for part of the year, well drained during the dry season.

  • Edaphohygrophilous: edaphophilous series on soils that are unusually wet or flooded most of the year, such as riverbanks, marsh areas, etc.

  • Edaphoxerophilous: edaphophilous series on especially dry or xeric soils.

Table 6.1 lists all series recognized in the Cantabrian Atlantic territory with climax woodlands as PNV, divided according to their presence in the different biogeographic subsectors.
Table 6.1

Biogeographical distribution (territories) of vegetation series with climax woodlands as PNV in the Cantabrian Atlantic territory

The abbreviation “-S.” at the end of every woodland community name, means Sigmetum. Columns correspond to: North Lusitania Sierra (NLS), South Galician-Portuguese (SG-P), North Galician-Portuguese (NG-P), Inner Galician (I G), North Galician-Asturian (NG-A), Central-East Oviedo (CEOv), Santanderian-Biscayan (Sa-Bi), East Basque (E B) and Navarran-Alavese (Na-Al). (Abbreviated names in italics: non-coastal territories)

Throughout the Cantabrian Atlantic subprovince it is very common that the woodlands which represent the PNV are much altered or completely gone from the territory and replaced most of the times by shrub stages (see Sect. 6.4). Although the diversity of seral shrub communities replacing mature woodlands in a territory is quite large, good correlations between them can be found when addressing this diversity at the level of phytosociological alliances, as shown in Table 6.2.
Table 6.2

Main seral corresponding stages of vegetation series present in the Cantabro Atlantic territory. Table A: Climatophilous series, temporihygrophilous & edaphoxerophilous series, and Table B: Edaphohygrophilous series & Woodland permaseries

A

Serie number

Mature woodland

Secondary woodland

Tall heath/scrub

Low heath/scrub

Herbaceous vegetation

1

Hyperico androsaemi-Quercetum roboris

Corylus avellana community

Ulici-Cytision striati

Ericion umbellatae +

Cynosurion cristati

Frangulo-Pyrion cordatae

Daboecion cantabricae

2

Rusco aculeati-Quercetum roboris

Betulion fontqueri-celtibericae

Ulici-Cytision striati + Arbuto-Laurion

Daboecion cantabricae

Cynosurion cristati

3

Viburno tini-Quercetum roboris

Cytiso grandiflori-Arbutetum unedonis

Ulici-Cytision striati

Ericion umbellatae

Cynosurion cristati

4

Vaccinio myrtilli-Quercetum roboris

Betulion fontqueri-celtibericae

Ulici-Cytision striati

Daboecion cantabricae

Cynosurion cristati

5

Blechno spicantis-Quercetum roboris

Betulion fontqueri-celtibericae

Frangulo-Pyrion cordatae

Daboecion cantabricae

Cynosurion cristati

Ulici-Cytision striati

6

Hyperico pulchri-Quercetum roboris

Betulion fontqueri-celtibericae

Frangulo-Pyrion cordatae

Daboecion cantabricae

Cynosurion cristati

Arbuto-Laurion nobilis

7

Crataego laevigatae-Quercetum roboris

Unknown

Pruno-Rubion ulmifolii

Unknown

Potentillo-Brachypodion Cynosurion cristati

8

Pulmonario longifoliae-Quercetum petraeae

Betulion fontqueri-celtibericae

Cytision multiflori

Daboecion cantabricae

Cynosurion cristati

9

Lonicero periclymeni- Quercetum pyrenaicae

Betulion fontqueri-celtibericae

Ulici-Cytision striati + Arbuto-Laurion

Daboecion cantabricae

Cynosurion cristati

10

Melampyro pratensis- Quercetum pyrenaicae

Betulion fontqueri-celtibericae

Frangulo-Pyrion cordatae

Daboecion cantabricae

Cynosurion cristati

11

Roso arvensis-Quercetum pubescentis

Pinus sylvestris community

Pruno-Rubion ulmifolii

Genistion occidentalis

Potentillo-Brachypodion

Arrhenatherion elatioris

12

Pulmonario longifoliae-Quercetum fagineae

Unknown

Pruno-Rubion ulmifolii

Genistion occidentalis

Potentillo-Brachypodion

13

Saxifrago spathularis-Fagetum sylvaticae

Betulion fontqueri-celtibericae

Ulici-Cytision striati

Daboecion cantabricae

Cynosurion cristati

14

Carici caudatae-Fagetum sylvaticae

Betulion fontqueri-celtibericae

Pruno-Rubion ulmifolii

Genistion occidentalis

Potentillo-Brachypodion

Rhamno-Berberidion

15

Saxifrago hirsutae-Fagetum sylvaticae

Betulion fontqueri-celtibericae

Cytision multiflori

Daboecion cantabricae

Violion caninae

16

Carici sylvaticae-Fagetum sylvaticae

Betulion fontqueri-celtibericae

Pruno-Rubion ulmifolii

Genistion occidentalis

Potentillo-Brachypodion Arrhenatherion elatioris

Rhamno-Berberidion

17

Epipactido helleborines-Fagetum sylvaticae

Betulion fontqueri-celtibericae

Pruno-Rubion ulmifolii

Genistion occidentalis

Potentillo-Brachypodion

18

Hedero hibernicae-Fraxinetum angustifolii

Unknown

Pruno-Rubion ulmifolii

Unknown

Cynosurion cristati

19

Omphalodo nitidae-Fraxinetum angustifolii

Unknown

Pruno-Rubion ulmifolii

Unknown

Cynosurion cristati

20

Fraxino angustifolii-Ulmetum glabrae

Unknown

Pruno-Rubion ulmifolii

Unknown

Cynosurion cristati

21

Polysticho setiferi-Fraxinetum excelsioris

Betulion fontqueri-celtibericae

Pruno-Rubion ulmifolii

Genistion occidentalis

Arrhentherion elatioris

Cynosurion cristati

22

Hyperico androsaemi-Ulmetum glabrae

Betulion fontqueri-celtibericae

Pruno-Rubion ulmifolii

Unknown

Unknown

23

Viburno lantanae-Ulmetum minoris

Unknown

Pruno-Rubion ulmifolii

Unknown

Brachypodion phoenicoidis

24

Eryngio juresiani-Betuletum celtibericae

Unknown

Cytision multiflori

Daboecion cantabricae

V iolion caninae

25

Physospermo cornubiensis-Quercetum suberis

Ericion arboreae

Pruno-Rubion ulmifolii

Ericion umbellatae

Agrostion castellanae

Ulici-Cytision striati

26

Genisto hystricis-Quercetum rotundifoliae

Non-existent

Ericion arboreae

Ulici-Cistion ladaniferi

Agrostion castellanae

27

Arenario montanae-Quercetum suberis

Non-existent

Ulici-Cytision striati

Daboecion cantabricae

Sedion anglici

28

Genisto falcatae-Quercetum rotundifoliae

Non-existent

Pruno-Rubion ulmifolii

Non-existent

Potentillo-Brachypodion

29

Lauro nobilis-Quercetum ilicis

Arbuto-Laurion

Pruno-Rubion ulmifolii

Genistion occidentalis

Potentillo-Brachypodion

B

Serie number

Mature woodland

Tall scrub

Herbaceous vegetation

30

Senecioni bayonnensis-Alnetum glutinosae

Pruno-Rubion ulmifolii

Cynosurion cristati, Juncion acutiflori

31

Carici lusitanicae-Alnetum glutinosae

Salix atrocinerea community

Magnocaricion elatae

32

Galio broteriani-Alnetum glutinosae

Pruno-Rubion ulmifolii

Cynosurion cristati, Juncion acutiflori

33

Valeriano pyrenaicae-Alnetum glutinosae

Pruno-Rubion ulmifolii

Filipendulion ulmariae, Cynosurion cristati

34

Hyperico androsaemi-Alnetum glutinosae

Pruno-Rubion ulmifolii

Filipendulion ulmariae, Calthion palustris

35

Lonicero xylostei-Alnetum glutinosae

Pruno-Rubion ulmifolii

Filipendulion ulmariae, Potentillion anserinae

36

Valeriano pyrenaicae-Fraxinetum excelsioris

Pruno-Rubion ulmifolii

Cynosurion cristati, Juncion acutiflori

37

Carici pendulae-Fraxinetum excelsioris

Pruno-Rubion ulmifolii

Filipendulion ulmariae, Potentillion anserinae

38

Violo palustris-Betuletum pubescentis

Erica arborea-Frangula alnus community?

Cynosurion cristati, Juncion acutiflori

39

Carici reuterianae-Betuletum celtibericae

Frangulo-Pyrion cordatae

Cynosurion cristati, Juncion acutiflori

40

Salicetum salviifoliae

Non-existent

Glycerio-Sparganion neglecti

41

Salicetum angustifolio-albae

Non-existent

Potentillion anserinae,

42

Salicetum discoloro-angustifoliae

Non-existent

Senecionion fluviatilis

43

Omphalodo nitidae-Lauretum nobilis

Non-existent

Unknown

44

Calluno vulgaris-Lauretum nobilis

Non-existent

Unknown

45

Holco mollis-Lauretum nobilis

Non-existent

Unknown

46

Tamo communis-Lauretum nobilis

Non-existent

Potentillo-Brachypodion

47

Hedero helicis-Lauretum nobilis

Non-existent

Potentillo-Brachypodion

48

Lithodoro diffusae-Oleetum europaeae

Non-existent

Potentillo-Brachypodion

Series numbers are the same as used in Table 6.1

Regarding the climatophilous series, two categories can be recognized associated with the richness and availability of nutrients in the soil where they thrive: the baso-neutrophilous series on base-rich substrates, and the acidophilous series on soils poor in cations. As a rule, the former ones have seral stages with spiny/thorny shrub communities (class Rhamno-Prunetea spinosae) belonging to the alliance Pruno spinosae-Rubion ulmifolii, or even the Rhamno alpini-Berberidion vulgaris in the supratemperate belt. By contrast, the acidophilic series usually have as a first seral stage a broom formation (class Cytisetea scopario-striati, alliance Ulici europaei-Cytision striati or Cytision multiflori); but they can also be replaced by more oligotrophic shrub formations of the Rhamno-Prunetea class, such as the thickets of the alliance Frangulo alni-Pyrion cordatae. Naturally, most of the baso-neutrophilous series occur in the central-eastern territories where calcareous substrates are abundant: the Navarran-Alavese, East Basque, Santanderian-Biscayan and Central-East Oviedo territories. In both types of climatophilous series, either acidophilous or baso-neutrophilous, a pre-climax community may develop as a response to forest clearings resulting from natural or artificial causes, and in which there is no alteration in terms of soil conditions; such pre-climax communities are often dominated by Betula pubescens subsp. celtiberica and Salix sp. pl. in oligotrophic series and Corylus avellana in the meso-eutrophic ones, but in either case the communities described until recently were placed in the same alliance Betulion fontqueri-celtibericae. (Figs. 6.25 and 6.26)
Fig. 6.25

Different beech woodland series are derived from different geological substrates. Calcicolous beech woodland series (Carici sylvaticae-Fago sylvaticae sigmetum) with thorny scrub (Pruno-Rubion ulmifolii), grazed pastures (Potentillo-Brachypodion rupestris) and with visible hints of limestone at Llano de Urbasa (Navarra)

Fig. 6.26

Silicicolous beech woodland series (Saxifrago spathularis-Fago sylvaticae sigmetum) with the upper border of the forest mantled by birch prewoodland (Betulion fontqueri-celtibericae), shrubland of Erica arborea (Ulici-Cytision striati) and a mosaic of Erica mackaiana heathland (Daboecion cantabricae) and hygrophilous grassland (Violion caninae) where a cow is grazing in the foreground; Carondio Range (Allande, Asturias)

The Mediterranean evergreen and sclerophyllous forests communities can be considered as biogeographic singularities, occurring as edaphoxerophilous series (Lauro nobilis-Querco ilicis-S., Genisto falcatae-Querco rotundifoliae-S.) but also as climatophilous series associated with the exceptional mesomediterranean bioclimate (Genisto hystricis-Querco rotundifoliae-S., Physospermo cornubiensis-Querco suberis-S.) present only in the Inner Galician territory (Fig. 6.27). The seral shrub stages can range from thorny communities of the Pruno spinosae-Rubion ulmifolii on limestone substrates, to retamoid scrub of the Cytision multiflori and even shade-tolerant thickets of the Ericion arboreae under a mesomediterranean climate. In the holm oak calcareous woodlands of the Lauro-Quercetum ilicis we can find pre-climax arboreal formations of the Arbuto unedonis-Laurion nobilis alliance, from the Quercetea ilicis class.
Fig. 6.27

Edaphoxerophilous cork oak series (Arenario montanae-Querco suberis sigmetum) developed at rocky and southerly exposed slopes at the Navia river valley; Tamagordas (Asturias)

For identification and mapping of the different vegetation series and in the absence of the mature stage (the woodland community heading this series) or its pre-climax shrub mantles, the shrub communities replacing those referred to above in a situation of more intense anthropogenic degradation can be used as a diagnostic element. The baso-neutrophilous series have scrublands of the alliance Genistion occidentalis (class Festuco hystricis-Ononidetea striatae), which are completely absent in acidophilic series, where they are replaced by heathlands of the Daboecion cantabricae or, in areas with a temperate sub-Mediterranean climate, by heathlands of the Ericion umbellatae (class Calluno-Ulicetea). The original mesomediterranean series of Quercus rotundifolia woodlands are also an exception in this case, being replaced by scrub of a more sclerophyllous nature of the alliance Ulici argentei-Cistion ladaniferi (class Cisto-Lavanduletea stoechadis).

In many cases edaphohygrophilous woodlands have been replaced by meadows or other herbaceous communities, for agricultural and pastoral purposes; therefore, the identifiable replacement communities of those woodlands are woody shrub formations normally occurring in edges of the woodland or a seral stage of perennial grasslands (Molinio-Arrhenatheretea or Festuco-Brometea classes, see Sect. 6.5).

Riparian series with willows (Salix sp. pl.) woodlands as PNV, colonizing streambanks, often lack the shrub stage replacement, having only a perennial herbaceous community as substitute.

Just as in the edaphohygrophilous series, the climax woodlands of the temporihygrophilous series have been seriously affected by deforestation for the sake of croplands or permanent grasslands. In many cases this prevents the identification of the progressive seral stages and the dynamics of the whole series. In others, the PNV is only identifiable from scarce individuals of the association persisting in hedges inserted between extensive crop fields and grasslands for livestock grazing. This is a process which particularly affects the series dominated by Ulmus minor and Fraxinus angustifolia (Table 6.2-A, series 18, 19, 20 & 23).

6.7.1 Woody Permaseries

Throughout the entire Cantabrian Atlantic territory, especially near the shoreline and other thermoxerophilous environments, some communities have been located and studied whose origin and floristic affinities may relate them to the typical Mediterranean evergreen vegetation (class Quercetea ilicis) (Bueno & Fernández-Prieto 1991, Loidi et al. 1994, Honrado et al. 2003, Álvarez-Arbesú 2005, Rodríguez-Guitián et al. 2007). These are communities dominated by evergreen trees, mainly Laurus nobilis and exceptionally Olea europea var. sylvestris, in small patches of woodlands in particularly dry or steep and rocky biotopes. They behave as permanent communities, thus without any other woody seral stage than the present community. Although they are confined to small sporadic spots, their importance is enormous as they are relict vegetation reflecting paleoclimatic conditions dating back to the Pleistocene (Rodríguez-Guitián et al. 2007). All these associations belong to the alliance Arbuto unedonis-Laurion nobilis included in Table 6.2-B as permaseries (Permasigmetum). It should be noted that such relict formations occur in almost all coastal biogeographical units referred to as “territories” (Fig. 6.28). Several of these permaseries have been recognized and described in relatively recent times, so, understandably, only the composition of their mature formations has been studied and much is unknown about the seral herbaceous communities, as these biotopes are small and have very fragmented geographic distributions.
Fig. 6.28

Permaseries of laurel-tree woodlands (Calluno vulgaris-Lauro nobilis sigmetum) on a low siliceous littoral cliff at O Vicedo (Lugo, Galicia)

The set of woody Permaseries occurring in the form of very small patches of woodland can be completed with some, also evergreen, formations dominated by Arbutus unedo. They were described from the Basque Country to Portugal as more or less dense and frequent formations, constituting various associations integrated mostly in the alliance Arbuto unedonis-Laurion nobilis (Díaz-González and Fernández-Prieto 1994; Loidi et al. 1994; Aguiar and Capelo 1995; Rodríguez-Guitián et al. 2007). But in most cases such formations have been described as seral stages of mature forests and only exceptionally as permanent communities found on rocky outcrops and other geomorphologically particular positions.

References

  1. Aedo C, Diego C, García Codrón JC, Moreno G (1991) El bosque en Cantabria. Universidad de Cantabria. Asamblea Regional de Cantabria, SantanderGoogle Scholar
  2. Aguiar C, Capelo J (1995) Anotação sobre a posição fitossociológica dos medronhais do alto Minho. Silva Lusitana 3:123–125Google Scholar
  3. Álvarez-Arbesú R (2005) La cubierta vegetal de los acantilados asturianos. Publ. Dpto. Biol. Org. Sists. Universidad de Oviedo, p 199Google Scholar
  4. Amigo J, Romero-Buján MI (1998) Abedulares de origen antrópico en Galicia: caracterización fitosociológica. Studia Botanica 17:37–51Google Scholar
  5. Amigo J, Guitián J, Fernández-Prieto JA (1987) Datos sobre los bosques ribereños de aliso (Alnus glutinosa) cántabro-atlánticos ibéricos. Publ. Univ. La Laguna. Ser. Informes 22:159–176Google Scholar
  6. Amigo J, Giménez de Azcárate J, Romero-Buján MI (1994) Omphalodo nitidae-Coryletum avellanae, a new mesophytic woodland community of the northwest Iberian Peninsula. Botanica Helvetica 104:103–122Google Scholar
  7. Amigo J, Pulgar I, Izco J (2009) Evidence of riverside ash tree forests in southern Galicia (northwestern Spain). Lazaroa 30:181–189Google Scholar
  8. Arnáiz C, Loidi J (1983) Sintaxonomía de la Pruno-Rubion ulmifolii (Prunetalia) en España. Lazaroa 4:17–22Google Scholar
  9. Aseginolaza C, Gómez D, Lizaur X, Montserrat G, Morante G, Salaverria M, Uribe-Echebarria P (1989) Vegetación de la Comunidad Autónoma del País Vasco. Gobierno Vasco, Vitoria-Gasteiz, p 361Google Scholar
  10. Bellot F (1968) La vegetación de Galicia. Anal. Inst. Bot. Cavanilles 24:3–306Google Scholar
  11. Bellot F, Casaseca B (1956) Contribución al estudio fitosociológico de los prados gallegos. Trab. Jard. Bot. Santiago de Compostela 8:1–40Google Scholar
  12. Berastegi A (2013) Prados y pastizales en Navarra: descripción, tipificación y ecología. Guineana 19:1–505Google Scholar
  13. Berastegi A, Darquistade A, García-Mijangos I (1997a) Biogeografía de la España centro-septentrional. Itinera Geobotanica 10:149–182Google Scholar
  14. Berastegi A, García-Mijangos I, Darquistade A, Loidi J (1997b) Nuevos datos sobre los bosques secundarios (prebosques) del sector cántabro-euskaldún. Lazaroa 18:165–172
  15. Biurrun I (1999) Flora y vegetación de los ríos y humedales de Navarra. Guineana 5:1–338. Universidad del País VascoGoogle Scholar
  16. Biurrun I, Campos JA, García-Mijangos I, Herrera M, Loidi J (2011) Nuevos datos sobre los bosques de barrancos y pies de cantil (Tilio-Acerion) del País Vasco y regiones limítrofes. Actes del IX Col-loqui Internacional de Botànica Pirenaico-Cantàbrica a Ordino, Andorra, pp 64–74Google Scholar
  17. Braun-Blanquet J (1967) Vegetationsskizzen aus dem Baskenland mit Ausblicken auf das weitere Ibero-Atlantikum. II Teil. Vegetatio 14(1–4):1–126Google Scholar
  18. Bueno A (1997) Flora y vegetación de los estuarios asturianos. Cuadernos de Medio Ambiente, Naturaleza. Oviedo 3:1–334Google Scholar
  19. Bueno A, Fernández-Prieto JA (1991) Acebuchales y lauredales de la costa cantábrica. Lazaroa 12:273–302Google Scholar
  20. Clements FE (1916) Plant succession: An analysis of the development of the vegetation. Carnegie Institute, Publication n° 242. Washington DC, p 515Google Scholar
  21. Costa J C, Aguiar C, Capelo J, Lousã M, Neto C (1998a) Biogeografia de Portugal Continental. Quercetea 0:5–56Google Scholar
  22. Costa JC, Capelo J, Lousã M, Espírito Santo MD (1998b) Sintaxonomia da vegetação halocasmofítica das falesias marítimas portuguesas (Crithmo-Staticetea Br.-Bl. 1947). Itinera Geobotanica 11:227–247Google Scholar
  23. Costa JC, Capelo J, Lousã M, Antunes JH, Castro Aguiar C, Izco J, Ladero M (2000) Nota acerca os giestais da Ulici europaei-Cytision striati Rivas-Martínez, Díaz, Fernández-González & Loidi em Portugal Continental. Silva Lusitana 8(1):120–128Google Scholar
  24. Costa JC, López MC, Capelo J, Lousã M (2001) Sintaxonomia das comunidades de Prunus lusitanica L. subsp. lusitanica no ocidente da Península Ibérica. Silva Lusitana 8(2):253–263Google Scholar
  25. Costa JC, Aguiar C, Capelo J, Lousã M, Antunes J, Castro H, Honrado J, Izco J, Ladero M (2004) A clase Cytisetea scopario-striati em Portugal Continental. Quercetea 4:45–70Google Scholar
  26. Costa JC, Honrado J, Monteiro-Henriques T, Neto C, Aguiar C (2008) As comunidades de Pterospartum tridentatum sensu lato em Portugal Continental. Silva Lusitana 16(1):123–127Google Scholar
  27. Costa JC, Neto C, Aguiar C, Capelo J, Espírito Santo MD, Honrado J, Pinto-Gomes C, Monteiro-Henriques T, Sequeira M, Lousã M (2012) Vascular plant communities in Portugal (continental, the Azores and Madeira). Global Geobotany 2:1–180Google Scholar
  28. Darquistade A, Berastegi A, Campos JA, Loidi J (2004) Pastizales supratemplados cántabro-euskaldunes de Agrostis curtisii: caracterización y encuadre fitosociológico. Silva Lusitana 12(2):135–149Google Scholar
  29. Díaz-González TE (1998) Síntesis de la vegetación arbustiva de Europa Occidental. I: Brezales (Calluno-Ulicetea). Itinera Geobotanica 11:7–31Google Scholar
  30. Díaz-González TE (2009) Caracterización de los Hábitats de Interés Comunitario (Red Natura 2000) existentes en el Principado de Asturias. I: Hábitats litorales halófilos (dunas, acantilados y marismas). Bol. Cien. Nat. R.I.D.E.A. 50:223–280Google Scholar
  31. Díaz-González TE (2010a) Caracterización de los hábitats de interés comunitario (Red Natura 2000) existentes en Asturias. II: Bosques y arbustedas arborescentes. Bol. Cien. Nat. R.I.D.E.A. 51:213–276Google Scholar
  32. Díaz-González TE (2010b) Tejos y tejedas: un patrimonio natural y cultural que debemos conservar y proteger. Revista Peña Santa 6:72–82Google Scholar
  33. Díaz-González TE, Fernández-Prieto JA (1994) La vegetación de Asturias. Itinera Geobotanica 8:243–528Google Scholar
  34. Diemont WH, Webb NR, Degn HJ (1996) A pan-European view on heathland conservation. Proceedings of the National Heathland Conference 1996. English Nature, PeterboroughGoogle Scholar
  35. Ellenberg HH (1988) Vegetation ecology of Central Europe, 4th edn. Cambridge University Press, Cambridge, p 753Google Scholar
  36. Fernández-Areces MP, Pérez-Carro FJ, Díaz-González TE (1987) Estudio del Cheilanthion hispanicae Rivas Goday 1955 em. Sáenz de Rivas & Rivas-Martínez 1979 y comunidades afines, en el sector Orensano-Sanabriense (Provincia Carpetano-Ibérico-Leonesa). Lazaroa 7:207–220Google Scholar
  37. Fernández-Prieto JA, Díaz-González TE (2003) Las clasificaciones de los hábitats naturales de la Unión Europea y la Directiva Hábitats. Las formaciones leñosas altas atlánticas ibéricas. Naturalia Cantabricae 2:25–32Google Scholar
  38. Fernández-Prieto JA, Loidi J (1984) Estudio de las comunidades vegetales de los acantilados costeros de la cornisa cantábrica. Documents Phytosociologiques 8:185–218Google Scholar
  39. Giménez de Azcárate J, Romero-Buján MI, Amigo J (1996) Los espinales de la Pruno-Rubion ulmifolii en Galicia. Lazaroa 16:89–104Google Scholar
  40. Heras FT, Infante M (2004) La turbera cobertor del Zalama (Burgos-Vizcaya): un enclave único en riesgo de desaparición. Est. Mus.Cienc. Nat. de Álava 18-19:49–57Google Scholar
  41. Herrera M (1995) Estudio de la vegetación vascular de la cuenca del Río Asón. Guineana 1. Universidad del Pais Vasco, p 435Google Scholar
  42. Herrera M, Fernández-Prieto JA, Loidi J (1991) Orlas arbustivas oligotróficas cantábricas: Frangulo alni-Pyretum cordatae. Stvdia Botanica 9:17–23Google Scholar
  43. Honrado J (2003) Flora e Vegetação do Parque Nacional da Peneda-Gerês. Ph. Thesis. Faculdade de Ciências, Universidade do Porto, Porto, p 540Google Scholar
  44. Honrado J, Alves P, Nepomuceno-Alves H, Barreto-Caldas F (2002) Ten new syntaxa from the Miniensean biogeographic subsector (Northwestern Portugal). In: Notas do Herbário da Estação Florestal Nacional (LISFA). Silva Lusitana 10(2):247–259Google Scholar
  45. Honrado J, Alves P, Aguiar C, Ortiz S (2003) Juresian riparian birch woodlands: Carici reuterianae-Betuletum celtibericae ass. nova. In: Notas do Herbário da Estação Florestal Nacional (LISFA). Silva Lusitana 11:237–241Google Scholar
  46. Honrado J, Alves P, Nepomuceno-Alves H, Barreto-Caldas F (2004) A vegetação do alto Minho. Esboço fitossociológico da vegetação natural do extremo Noroeste de Portugal (sectores Galaico-Português e Geresiano). Quercetea 5:3–102Google Scholar
  47. Honrado J, Pulgar I, Alves P, Ortiz S (2012) Phalacrocarpo oppositifolii-Silenetum acutifoliae ass. nova hoc loco. In Costa JC Neto C Aguiar C, Capelo J Espírito Santo MD Honrado J, Pinto-Gomes C, Monteiro-Henriques T, Sequeira M, Lousã M (eds) Vascular plant communities in Portugal (continental, the Azores and Madeira). Global Geobotany 2:97–98Google Scholar
  48. Ihobe (Sociedad Pública del Departamento de Medio Ambiente, Planificación Territorial, Agricultura y Pesca del Gobierno Vasco) (2011) Primera evaluación del estado de conservación de los hábitats de bosque de interés comunitario en el País Vasco. BilbaoGoogle Scholar
  49. Izco J, Guitián J (1984) Los prados de siega con Malva moschata (Arrhenatherion elatioris) en Galicia. Pastos 12(2):255–264Google Scholar
  50. Izco J, Ortiz S (1985) El mosaico pastizal-esteval (jaral de Cistus ladanifer L.) en Galicia. Bol. Soc. Brot. 58:115–138Google Scholar
  51. Izco J, Sánchez JM (1996) Los medios halófilos de la ría de Ortigueira (A Coruña, España). Vegetación de dunas y marismas. Thalassas 12:63–100Google Scholar
  52. Izco J, Amigo J, Guitián J (1990a) Los robledales Galaico-Septentrionales. Acta Bot. Malacitana 15:267–276Google Scholar
  53. Izco J, Amigo J, Guitián J (1990b) Composición, relaciones y sistematización de los bosques esclerofilos del noroeste ibérico. Not. Fitosoc. 22:83–114Google Scholar
  54. Izco J, Guitián P, Sánchez JM (1993a) Análisis y clasificación de las comunidades vegetales vivaces de las dunas vivas gallegas. Rev. Acad Galega Ciencias 12:79–104Google Scholar
  55. Izco J, Guitián P, Sánchez JM (1993b) La marisma superior cántabro-atlántica meridional: estudio de las comunidades de Juncus maritimus y de Elymus pycnanthus. Lazaroa 13:149–169Google Scholar
  56. Izco J, Amigo J, García-San León D (1999) Análisis y clasificación de la vegetación leñosa de Galicia (España). Lazaroa 20:29–47Google Scholar
  57. Izco J, Amigo J, García San-León D (2001a) Análisis y clasificación de la vegetación de Galicia (España) II. La vegetación herbácea. Lazaroa 21:25–50Google Scholar
  58. Izco J, Díaz-Varela R, Martínez-Sánchez S, Rodríguez-Guitián MA, Ramil-Rego P, Pardo-Gamundi I (2001b) Análisis y valoración de la Sierra de O Xistral: un modelo de aplicación de la Directiva Hábitat en Galicia. Consellería de Medio Ambiente. Xunta de Galicia. Santiago de Compostela, p 162Google Scholar
  59. Izco J, Amigo J, Ramil-Rego P, Díaz-Varela R (2007) Brezales: biodiversidad, usos y conservación. Recursos Rurais 2:1–19Google Scholar
  60. Izco J, Amigo J, Pulgar I (2009) Violion caninae grasslands (Nardetea strictae) in the North and North-West of Spain. Acta Bot. Gallica 156(3):437–454CrossRefGoogle Scholar
  61. Loidi J (1983) Datos sobre la vegetación de Guipúzcoa (País Vasco). Lazaroa 4:63–90Google Scholar
  62. Loidi J, Báscones JC (2006) Memoria del Mapa de Series de Vegetación de Navarra. E 1:200.000. Departamento de Medio Ambiente, Ordenación del Territorio y Vivienda. Gobierno de Navarra.Google Scholar
  63. Loidi J, Herrera M, Olano JM, Silván F (1994) Maquis vegetation in the eastern Cantabrian coastal fringe. J. Veg. Sci. 5(4):533–540CrossRefGoogle Scholar
  64. Loidi J, Biurrun I, Herrera M (1997a) La vegetación del centro-septentrional de España. Itinera Geobotanica 9:161–618Google Scholar
  65. Loidi J, García-Mijangos I, Herrera M, Berastegi A, Darquistade A (1997b) Heathland vegetation of the northern-central part of the Iberian Peninsula. Folia Geobot. Phytotax. 32:259–281CrossRefGoogle Scholar
  66. Loidi J, Biurrun I, Campos JA, García-Mijangos I, Herrera M (2007) A survey of heath vegetation of the Iberian Peninsula and Northern Morocco: a biogeographic and bioclimatic approach. Phytocoenologia 37(3–4):341–370CrossRefGoogle Scholar
  67. Loidi J, Biurrun I, Campos JA, García-Mijangos I, Herrera M (2010) A biogeographical analysis of the European Atlantic lowland heathlands. J. Veg. Sci. 21:832–842Google Scholar
  68. Loidi J, Biurrun I, Campos J A, García-Mijangos I, Herrera M (2011) La vegetación de la Comunidad Autónoma del País Vasco. Leyenda del mapa de series de vegetación a escala 1:50.000. Ed. Universidad del País Vasco (electronic version).Google Scholar
  69. Loriente E (1974) Vegetación y flora de las playas y dunas de la provincia de Santander. Inst. Cul. Cantabria, Dip. Prov. Santander, p 287Google Scholar
  70. Monteiro-Henriques T, Costa JC, Bellu A, Aguiar C (2010) Fraxino angustifoliae-Ulmetum glabrae: an original endemic and extremely localized forest from mainland Portugal. Braun-Blanquetia 46:323–327Google Scholar
  71. Monteiro-Henriques T, Martins MJ, Cerdeira JO, Silva P, Arsénio P, Silva Á, Bellu A, Costa JC (2015) Bioclimatological mapping tackling uncertainty propagation: application to mainland Portugal. Int. J. Climatol. doi: 10.1002/joc.4357 Google Scholar
  72. Moore JJ (1968) A classification of the bogs and wet heaths of northern Europe (Oxycocco-Sphagnetea Br.-Bl. & Tx. 1943). Ver. Int. Symp. Pflanzensoz. Stolzenau/Weser 1964:306–320Google Scholar
  73. Muñoz Sobrino C, Ramil-Rego P, Gómez-Orellana L, Díaz-Varela RA (2005) Palynological data on major Holocene climatic events in NW Iberia. Boreas 34(3):381–400CrossRefGoogle Scholar
  74. Neto C, Costa JC, Honrado J, Capelo J (2007) Phytosociologic associations and Natura 2000 habitats of Portuguese coastal sand dunes. Fitosociologia 44 (2) suppl. 1:29–35Google Scholar
  75. Onaindía M (1986) Ecología vegetal de las Encartaciones y Macizo del Gorbea (Vizcaya). Tesis Doctoral, Univ. País Vasco, p 271Google Scholar
  76. Peralta J, Biurrun I, García-Mijangos I, Remón JL, Olano JM, Lorda M, Loidi J, Campos JA 2013 Manual de Hábitats de Navarra. Departamento de Desarrollo Rural, Medio Ambiente y Administración Local. Gobierno de Navarra, Pamplona, p 576Google Scholar
  77. Pulgar I (1999) La vegetación de la Baixa Limia y Sierras del entorno. Tesis Doctoral. Fac. Farmacia, Univ. Santiago de Compostela, p 369Google Scholar
  78. Pulgar I, Manso D (2010) Datos sobre Prunus lusitanica L. (Rosaceae) en Galicia. Nova Acta Cient. Comp. (Biol.): 33–47Google Scholar
  79. Ramil-Rego P (1992) La vegetación cuaternaria de las Sierras Septentrionales de Lugo a través del análisis polínico. PhD. Facultad de Biología. Universidade de Santiago de Compostela, p 356Google Scholar
  80. Ramil-Rego P, Rodríguez-Guitián MA, Rodríguez-Oubiña J (1996) Valoración de los humedales continentales del NW Ibérico: caracterización hidrológica, geomorfológica y vegetacional de las turberas de las Sierras Septentrionales de Galicia. In: Pérez-Alberti A & Martínez-Cortizas A (eds) Avances en la reconstrucción paleoambiental de las áreas de montaña lucenses. Monografías G.E.P. n°1:166–187. Diputación Provincial de LugoGoogle Scholar
  81. Rivas Goday S, Rivas-Martínez S (1963) Estudio y clasificación de los pastizales españoles. Publ. Ministerio de Agricultura, Madrid, p 269Google Scholar
  82. Rivas-Martínez S (1987) Memoria del Mapa de Series de Vegetación de España. Serie Técnica n°1:9–208. ICONA. Madrid.Google Scholar
  83. Rivas-Martínez S (2002a) High syntaxa of Spain and Portugal and their characteristic species. In: Rivas-Martínez S, Díaz-González TE, Fernández-González F, Izco J, Loidi J, Lousã M, Penas A (eds) Vascular plant communities of Spain and Portugal, Addenda to the syntaxonomical checklist of 2001. ItineraGeobotanica 15(2):434–922Google Scholar
  84. Rivas-Martínez S (2002b) Review of definitions. In: Rivas-Martínez (on-line) Worldwide Bioclimatic Classification System. http://www.globalbioclimatics.org/book/review.htm. Accesed on 14 Feb 2015
  85. Rivas-Martínez S (2005) Avances en Geobotánica. In: Rivas-Martínez (on-line) Worldwide Bioclimatic Classification System. http://www.globalbioclimatics.org/book/ranf2005.pdf. Accesed on 14 Feb 2015
  86. Rivas-Martínez S (2007) Mapa de series, geoseries y geopermaseries de vegetación de España. Memoria del mapa de vegetación potencial de España. Parte I. Itinera Geobotanica 17:5–435Google Scholar
  87. Rivas-Martínez S (2011) Mapa de series, geoseries y geopermaseries de vegetación de España. [Memoria del mapa de vegetación potencial de España] Parte II. Itinera Geobotanica 18(1,2):1–800Google Scholar
  88. Rivas-Martínez S, Díaz-González TE, Fernández-Prieto JA, Loidi J, Penas A (1984) La vegetación de la Alta Montaña Cantábrica. Los Picos de Europa. Ediciones Leonesas, León, p 300Google Scholar
  89. Rivas-Martínez S, Cantó P, Izco J (2002) Petrocoptido pyrenaicae-Sarcocapnetea enneaphyllae classis nova hoc loco. In: Rivas-Martínez S, Díaz-González TE, Fernández-González F, Izco J, Loidi J, Lousã M, Penas A (eds) Vascular plant communities of Spain and Portugal, Addenda to the syntaxonomical Checklist of 2001. Itinera Geobotanica 15(1):156–166Google Scholar
  90. Rivas-Martínez S, Penas A, Díaz-González TE, Del Rio S, Cantó P, Herrero L, Pinto-Gomes C, Costa JC (2014) Biogeography of Spain and Portugal. Preliminary typological synopsis. International Journal of Geobotanical Research 4:1–64Google Scholar
  91. Rodríguez-Guitián MA (2005) Avaliación da diversidade sílvica do subsector galaico-asturiano septentrional: tipos de bosques, valor para a conservación e principais ameazas. Recursos Rurais. Serie cursos e monografias do IBADER 2:23–44Google Scholar
  92. Rodríguez-Guitián MA (2006) Acerca de la identidad fitosociológica de los hayedos silicícolas sublitorales del centro de la cornisa cantábrica. Lazaroa 27:59–78Google Scholar
  93. Rodríguez-Guitián MA (2010) Temperate riverside forests without alder trees at the NW of the Iberian peninsula: ecology, phytosociological profile and interest for preservation policies. Lazaroa 31:9–37CrossRefGoogle Scholar
  94. Rodríguez-Guitián MA, Ramil-Rego P (2007) Revisión de las clasificaciones climáticas aplicadas al territorio gallego desde una perspectiva biogegráfica. Recursos Rurais 1(3):31–53Google Scholar
  95. Rodríguez-Guitián MA, Amigo J, Romero-Franco R (2000) Aportaciones sobre la interpretación, ecología y distribución de los bosques supratemplados naviano-ancarenses. Lazaroa 21:51–71Google Scholar
  96. Rodríguez-Guitián MA, Ferreiro J, Negral MA, Merino A (2001) Distribución y ecología del haya (Fagus sylvatica L.) en el Subsector Galaico-Asturiano Septentrional (NW Ibérico). Actas del III Congreso Forestal Español. Mesas 1 y 2:201–207. GranadaGoogle Scholar
  97. Rodríguez-Guitián MA, Real C, Amigo J, Romero-Franco R (2003) The Galician-Asturian beechwoods (Saxifrago spathularidis-Fagetum sylvaticae): description, ecology and differentiation from other Cantabrian woodland types. Acta Bot Gallica 200:15–36Google Scholar
  98. Rodríguez-Guitián MA, Ramil-Rego P, Romero-Franco R (2007) Caracterización ecológica y florística de las comunidades lauroides del occidente de la Cornisa Cantábrica. Lazaroa 28:35–65Google Scholar
  99. Rodríguez-Guitián MA, Ramil-Rego P, Real C, Díaz-Varela R, Ferreiro da Costa J, Cillero C (2009) Caracterización vegetacional de los complejos de turberas de cobertor activas del SW europeo. In: Llamas F, Acedo C (eds) Botánica Pirenaico-Cantábrica en el siglo XXI. Área de Publicaciones. Universidad de León, León, pp 633–653Google Scholar
  100. Rodríguez-Guitián MA, Ramil-Rego P, Díaz-Varela R, Pereira-Espinel J, Real C (2010) Los bosques dominados por Taxus baccata L. del extremo occidental de la Cordillera Cantábrica: caracterización, valor de conservación y amenazas. Botànica Pirenaico-cantàbrica. Actes del IX Col·loqui Internacional de Botànica Pirenaico-Cantàbrica: 367–378. Ordino. Andorra.Google Scholar
  101. Romero-Buján MI (1993) La vegetación del valle del río Cabe (Terra de Lemos, Lugo). PhD, Facultad Biología, Univ. Santiago de Compostela, p 279Google Scholar
  102. Teles AN (1970) Os lameiros de montanha do norte de Portugal. Subsídios para a sua caracterização fitossociológica e química. Agronomia Lusitana 31:5–132Google Scholar
  103. Tüxen R, Oberdorfer E (1958) Die Pflanzenwelt Spaniens. II Teil. Eurosibirische Phanerogamen-Gesellschaften Spaniens. Veröff Geobot Inst Rübel Zürich 32:1–298Google Scholar
  104. Vera JA (ed) (2004) Geología de España. Sociedad Geológica de España-Instituto Geológico y Minero de España, Madrid, p 890Google Scholar
  105. Webb NR (1998) The traditional management of European heathlands. J Appl Ecol 35:987–990CrossRefGoogle Scholar

Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  • Javier Amigo
    • 1
  • Manuel Antonio Rodríguez-Guitián
    • 1
  • João Jose Pradinho Honrado
    • 2
  • Paulo Alves
    • 2
  1. 1.Universidade de Santiago de CompostelaSantiagoSpain
  2. 2.Universidade de PortoPortoPortugal

Personalised recommendations