Interactions between aridity and land-use on ecosystem functioning
In this study, we observed significant synergistic effects of aridity and overgrazing on plant species richness and SOC, as well as of aridity and haying on aboveground biomass (Table 1, Fig. 4). These findings suggest that the effects of land-use on grassland diversity and functioning can be altered by climate. Overgrazing is a pervasive driver of soil function loss (Bridges & Oldeman 1999), resulting in reductions in SOC and aboveground biomass in arid lands, while detrimental effects may be less pronounced in semiarid lands (Eldridge et al. 2011; Anadón et al. 2014). In this study, grazing and haying effects on ecosystem functioning were greater at more arid sites than those at more humid sites. This may be due to the higher diversity and plant recovery capacity in humid environments. The present results highlight that it is more important to preserve biodiversity in arid regions to alleviate the negative effects of land-use on grassland structure and ecosystem functioning, while biodiversity may be particularly threatened in arid lands.
Although there have been several studies on effects of diversity, aridity, and land-use on grassland functioning at the global scale (Maestre et al. 2012; Delgado-Baquerizo et al. 2013; McSherry & Ritchie 2013; Petz et al. 2014; Ruppert et al.2015), the joint and synergistic effects of these factors have not been examined at such a large scale as this study. Implications of our study can provide guidelines for mitigating the impacts of global change and improving adaptive grassland management. In the future, multi-factor experiments with grazing or haying intensities at such large scale and on the above-belowground mechanisms underlying these effects would provide a more comprehensive understanding for sustainable grassland management.