Tree - open grassland mosaics drive the herbaceous structure and diversity in Mediterranean wood pastures

Abstract Mediterranean wood pastures are seminatural savannahlike agroecosystems that result from traditional silvopastoral practices, which shaped these systems into a mosaic of trees and open grassland. However, traditional silvo-pastoral uses are declining with the implications that this may have on the herbaceous layer, which is a very diverse and valuable resource. Here, we aim at assessing the influence of the tree – open grassland mosaic on the structure, diversity, and composition of the herbaceous layer. Specifically, assessing the canopy effect (a) under representative Iberian canopy types, considering traditional Quercus species stands and Pinus pinea plantations at different locations; and (b) along seasonality. For that purpose, we carried out vegetation surveys in Mediterranean wood pastures of the south SouthWest of the Iberian Peninsula. Our results show that the different components of the herbaceous layer performed differential responses to the presence/absence of tree canopies, as for instance shows the dominance of grasses under the canopy, while legumes and forbs were favoured in the open grassland. Also, the study plots differed in their composition of species and species richness, with a certain a reduction in the species richness in the plot dominated by P. pinea compared to plots dominated by Quercus species. The canopy effect was more pronounced at the more environmentally constrained location. Such canopy effects were generally more pronounced in spring than in autumn. In conclusion, it is highly advisable preserve the tree – open grassland mosaic and traditional Quercus species stands to maximize and preserve plant specific and functional diversity and ecosystem functionality.