Land abandonment results in species richness loss and homogenization of belowground soil food webs

Land abandonment has been estimated to reach ~30 million hectares in 2030 in Europe. There is wide-spread concern that this will result in a further decrease in biodiversity and related loss in functioning, but the results to date are far from conclusive. Previous studies have shown that for aboveground communities, land abandonment can impact both alpha and beta diversity, but relative effects on alpha and beta-diversity (homogenization) of below ground communities have been poorly addressed. Here, we evaluate whether land abandonment leads to consistent changes in alpha diversity of belowground fauna across a wide range of soil fauna groups, using a range of molecular techniques. We sampled a series of paired grazed and ungrazed experimental sites that had been present between 10-85 years and were positioned along an 800-km long gradient in Britain. Our results indicate that grazers have consistent, positive effects on alpha diversity of all below ground groups, as well as vegetation, but a mixed effect on the homogeneity of microbial and soil fauna groups. Soil fauna groups exhibit a markedly different response to grazing as a homogenizing factor than microbial groups, thus emphasizing the need to increase variation in grassland management when aiming to conserve high biodiversity.