Species richness of vascular plants along the climatic range of the Spanish dehesas at two spatial scales

Abstract

Aims of study: The goals of this paper are to summarize and to compare plant species richness and floristic similarity at two spatial scales; mesohabitat (normal, eutrophic, and oligotrophic dehesas) and dehesa habitat; and to establish guidelines for conserving species diversity in dehesas.Area of study: We considered four dehesa sites in the western Peninsular Spain, located along a climatic and biogeographic gradient from north to south. Main results: Average alpha richness for mesohabitats was 75.6 species, and average alpha richness for dehesa sites was 146.3. Gamma richness assessed for the overall dehesa habitat was 340.0 species. The species richness figures of normal dehesa mesohabitat were significantly lesser than of the eutrophic mesohabitat and lesser than the oligotrophic mesohabitat too. No significant differences were found for species richness among dehesa sites. We have found more dissimilarity at local scale (mesohabitat) than at regional scale (habitat). Finally, the results of the similarity assessment between dehesa sites reflected both climatic and biogeographic gradients.Research highlights: An effective conservation of dehesas must take into account local and regional conditions all along their distribution range for ensuring the conservation of the main vascular plant species assemblages as well as the associated fauna.Keywords: Agroforestry systems; mesohabitat; non-parametric estimators; alpha richness; gamma richness; floristic similarity; climatic and biogeographic range.

Which Factors Favour Biodiversity in Iberian Dehesas?

“…Diversity values in eutrophic communities on valley bottoms were much lower, as expected due to the negative effect of grazing pressure, and maximal diversity values are associated with intermediate levels of grazing pressure. López-Carrasco et al [38] found a different pattern in same-sized plots (0.50 × 0.50 m): sites in valley bottoms had higher species richness values than higher zones on hilltops, while del Barrio et al [64] obtained similar results on large plots (1000 m 2 ). Here, grazing intensity plays an important role in the variation of species richness, which reaches a maximum with intermediate levels of disturbance; this factor may predominate over topography and the fertility gradient.…”