Conclusion
By analysing a comprehensive dataset of key belowground taxa, we show that cessation of grazing on montane grasslands with a long history of extensive sheep grazing leads to significant declines in ɑ-diversity of soil organisms, while β-diversity of soil fauna and soil microbes show a contrasting response. This illustrates that extensive grazing plays a key a role in regulating biodiversity of belowground communities, and highlights that the removal of grazing can result in a range of deleterious effects, much in line with recent work on aboveground invertebrate communities (Van Klink & WallisDeVries 2018). Large swarths of Europe are currently being subjected to ‘rewilding’, an approach to nature conservation that involves the cessation of historic livestock grazing. Our results suggest that such a ‘rewilding’ approach to nature conservation might not lead to an associated increase in the diversity of belowground organisms. Rather, given that current densities of natural grazers and browsers in historically grazed systems are low, particularly compared to previous interglacial periods (Sandom et al. 2014), we expect profound negative impacts of instantaneous cessation of grazing on belowground diversity. This suggest that there is a need for a gradual reduction of extensive grassland management and a gradual increase of natural grazers when aiming to conserve belowground biodiversity.
AcknowledgementsWe are extremely grateful to all landowners for allowing us to sample their sites and Jerry Tallowin for providing help in finding suitable research locations. Professor Rob Marrs is gratefully acknowledged for his assistance during the work at the various locations in the Peak District and Moor House, and we thank Aidan Keith, Centre for Ecology and Evolution, Lancaster, for granting access to the Tullgren extractors. Furthermore, we are grateful to all the people that assisted with field work: Ciska Veen, Eva Thuijsman, Jan Degenaar and all students from the HAS Hogeschool. MS was supported through an NWO Rubicon grant (2014.08) and facilitated by an International Exchange Award from the UK Biotechnology and Biological Sciences Research Council (BBSRC) (Grant BB/L026406/1) to RDB and NF.
Table 1. Site details for all 12 locations; numbers correspond to Fig. 1