Drove roads as local biodiversity reservoirs: Effects on landscape pattern and plant communities in a Mediterranean region

Question: What are the effects of traditional drove roads on landscape pattern and plant communities? Location: Madrid Autonomous Region, Central Spain. Methods: We selected four study localities in different landscape units. Within each locality, we selected eight sites and within each site, we established three 1-ha plots, each corresponding to one of three situations: drove road, adjacent matrix or distant matrix. The landscape pattern of each plot was characterized by the cover of the different patch types, the patch type richness ha-1 and the patch type evenness ha-1. At one site per locality, we also recorded vegetation by randomly distributing twenty 20 cm × 20 cm quadrats per plot. We characterized each quadrat by its species richness, plant species composition and plant functional composition. We also analysed species richness by constructing rarefaction curves for each plot. Results: In the localities situated in croplands, sub-mediterranean forests and coniferous forests, drove roads were found to be an important source of spatial heterogeneity and a reservoir for a large number of plant species. In contrast, drove roads did not differ from the matrix habitats in rangelands, suggesting that the processes shaping drove road vegetation are similar to the general processes that shape grazed systems. Drove roads did not imply a significant increase in functional diversity. Our results were heavily scale-dependent: while drove roads provided heterogeneity at the local scale, they showed a remarkable similarity at the large scale. Conclusions: Drove roads act as authentic local biodiversity reservoirs, especially in environments with low grazing levels. At the same time, drove roads imply structural and functional continuity on a large scale, increasing potential connectivity at the regional level. We recommend the preservation of drove roads in a functional state, because of their benefits to plant biodiversity conservation, and claim that these benefits should be considered when designing livestock policies with different intensification scenarios. © 2012 International Association for Vegetation Science.