At which spatial scale are plant species composition and diversity affected in beech forests?

Abstract

Landscape structure is crucial for forest conservation in regions where the natural forest is fragmented. Practical conservation is currently shifting from local stands to a landscape perspective, although few studies have tested the relative effects of different spatial scales on plant species composition and diversity in forests. We studied vascular plants and 17 predictor variables related to landscape (i.e. patch size or the surrounding landscape matrix) and stand conditions (i.e. soil pH and stand structure) in 50 semi-natural beech (Fagus sylvatica L.) forests in the northern Iberian Peninsula. We analysed the effect of landscape heterogeneity and stand-associated environmental conditions on plant species composition and diversity. Moreover, we studied the influence of these scales on the diversity of different life forms. Plant species composition and diversity responded primarily to suitable habitat proportions in the surrounding landscape and secondarily to soil pH. The response to these factors differed among life forms. Species diversity, especially tree and shrub diversity, increased with increases in the proportion of ecologically similar habitat in the surrounding landscape (forests dominated by Quercus spp.). Species diversity (primarily herb diversity) also increased with increasing soil pH. Future landscape management should seek to produce a heterogeneous matrix comprising patches of natural, unmanaged and managed deciduous forest and including other traditional uses and forest plantations.