Simulating long-term effects of abandonment on plant diversity in Mediterranean mountain farmland

<div><p>In this paper, long-term impacts of meadow abandonment scenarios on plant diversity were forecasted for high nature value farmland in northern Portugal, and implications for conservation planning and agri-environmental management are addressed. Vegetation patches representative of forests, meadows and edges, on mesic and wet soils, were surveyed for vascular plant diversity. Species richness and composition were compared across vegetation types, and additive partitioning was used to quantify hierarchic components of species richness. The implications of total and partial meadow abandonment were simulated according to landscape outcomes predicted for each scenario, and confirmed with a Monte-Carlo resampling. Forests hosted the highest number of species, as well as of exclusive species. Nonetheless, from the total pool (213), 21.6% were exclusive to meadows. Vegetation types generally shared small proportions of their species pools. With total meadow abandonment, a drastic decrease in total species richness (41.1%) and in endemic species richness (loss of 20.8%) was forecasted. However, only 12.3% of all species were forecasted to disappear under scenarios of partial abandonment. Landscape-level plant diversity can, therefore, be maintained by promoting farmland mosaics, even if the loss of scattered meadows in favour of native forests could be acceptable. Agri-environmental schemes should thus prioritize the maintenance of landscape heterogeneity.</p>