Short-term effects of non-grazing on plants, soil biota and aboveground-belowground links in Atlantic mountain grasslands

Mountain grasslands in the Iberian Peninsula are the result of extensive grazing. However, a progressive abandonment of grazing activity is currently observed in the study region. The objective of this work was to evaluate the short-term (2 years) effects of non-grazing on the diversity and composition of plants, soil microorganisms (prokaryotes, fungi, arbuscular mycorrhiza), mesofauna, macrofauna and aboveground-belowground links, through the study of 16 grazed vs. non-grazed areas in Atlantic grasslands located in the Basque Country (Spain). Sites were divided between 4 habitat types with different elevation, pasture productivity, vegetation type and parent material. Herbivores appeared to influence plant community composition, contributing to increase aboveground diversity, while having unequal effects on belowground communities depending on the organisms analysed. This may be explained by the different habitat and trophic level of each soil organism, which may be more or less affected by the predominating negative effects of grazing, such as soil compaction, and only partially compensated by other positive effects. Finally, habitat type appeared to be the strongest influence on both above-and belowground communities, also influencing the effect of the absence of grazing.