Site-Related Biocoenotic Dynamics
The dynamics of biota are largely dependent on the available habitats in a landscape while the heterogeneous distribution of resources is an essential reason for the constitution of ecological niches and for the structure and composition of communities. Vertical structures are marked within forest ecosystems with several strata, i.e. floor ground, herb, bush, and tree layers, which are reflected in the stratification of the animal community (Overgaard Nielsen 1987). Dead logs in the treetops offer other living conditions than dead wood lying on the ground. Animals that use different heterogeneously distributed resources must exhibit a high amount of spatial flexibility (Weidemann 1986).
The spatial distribution of habitats and microhabitats is the result of local relief and related soil texture, water and nutrient cycles, and the influence of light. A heterogeneous environment has different effects depending on the size of the organisms. Thus, it is better suited to small species than to large ones since it fosters the coexistence of small species more than that of larger ones (Levin 1974). Giller (1996) focused on fractal geometry for elucidating the differences in the niche structure of soil animals. Besides the environmental factors organisms themselves produce a plenitude of further structures.
A major part of the biocoenotic investigations, therefore, focused on the influence of the irregularly distributed habitats and on the dynamics of organisms (cf. Chapter 7). The dynamics of biota follow mostly seasonal dynamics, e.g. the leaf development of plants and the generation cycles of species, or long-term non-seasonal fluctuations. Animals in particular show seasonally controlled movements. Many animal species living in the vegetation during summer retreat into the soil in autumn or winter. Others migrate from agrarian ecosystems to forests for hibernating purposes. Seasonal movements are particularly wide-spread in a heterogeneous landscape. Long-term fluctuations may depend on successional changes of resources, i.e. the degradation of woody debris or leaf litter, or the succession of the vegetation after changing management practices.
KeywordsSpecies Richness Microbial Biomass Dead Wood Litter Layer Beech Forest
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