Large Habitat Range But Low Floristic Variation: The Case of Festuco rubrae-Agrostietum capillaris Grasslands

Abstract

We attempted to classify 414 grassland stands dominated by Festuca rubra and Agrostis capillaris in the southeastern Carpathian region and to infer the main ecological factors underlying the observed floristic variation. Several internal criteria were employed to select the optimal number of clusters resulting from applying the fuzzy C-medians algorithm to the Bray-Curtis distance matrix. Species fidelity, non-metric multidimensional scaling and relative importance of four plant functional groups were subsequently used to validate floristically and ecologically the clusters of relevés distinguished.

Sixty-five relevés were excluded from the final classification as being boundary or outlying communities with respect to cluster medoids. The remaining 349 relevés were assigned to five facies: potentillosum aureae (PA), loliosum perennis (LP), violosum caninae (VC), typicum (T ) and succisosum pratensis (SP). The strongest gradient detected runs from acidophilous grasslands (PA and LP) to those formed on base-rich substrates (VC and SP). A much weaker eco-floristic differentiation is induced by elevation and the predominant management type, i.e. colline-submontane meadows (LP and SP) versus montane-subalpine pastures (PA and VC). Unlike mega-forbs, the proportion of tall herbs, graminoids and legumes differs significantly between certain facies but also tends to discriminate between mown and grazed grasslands.

The facies distinguished herein are fuzzier and differ more or less from the five subassociations recently acknowledged in the literature through an empirical phytosociological classification. Although we did not consider relevés in which third-party species were dominant, our data set contained some noise due to inconsistencies in the occurrence patterns of grazing-tolerant and ruderal species. The fuzzy clustering output is less useful as a typological reference but provides a good basis for unravelling successional pathways under different environmental conditions and grassland use modes.