Effects of land-use on ecosystem functioning through plant diversity
Partially consistent with our hypothesis, overgrazing reduced plant species richness and ecosystem functions, whereas haying increased species richness and reduced aboveground biomass, but had no significant effect on SOC (Fig. 2). Despite the plant’s capacity for compensatory growth, overgrazing has resulted in widespread decline in biodiversity and ecosystem functioning and services in grasslands worldwide (Milchunas & Lauenroth 1993; Díaz et al. 2007; McSherry & Ritchie 2013; Erb et al. 2017). As a consequence, overgrazing has been reported to decrease plant species diversity, productivity, and SOC, and to alter C, N, and P pools and stoichiometry of steppe ecosystems (Gallardo & Schlesinger 1992; Bridges & Oldeman 1999; Asneret al. 2004; Bai et al. 2007; Bai et al. 2012). In this study, the negative effects of grazing on plant species richness, aboveground biomass, and SOC may result from overgrazing for most sites of this region (Liu & Diamond 2005; Han et al. 2008; Yanet al. 2013), although we lack data on accurate grazing intensity for this study. The differential effects of grazing and haying can be attributed to their different influence on dominant perennial grasses in this region (Fig. S2), which is dominated by Stipasbaicalensis , S. grandis , S krylovii , Leymus chinensis etc. The hay harvest occurs every year over many years, which reduces the resource store of the perennial species for regeneration and aboveground biomass in the following growing season (Wyka 1999; Klimeš & Klimešová 2001; Klimešová et al. 2017). In addition, haying typically occurs during a time of the year, when most other species have reached their peak productivity and finished seed reproduction. As a consequence, haying may particularly reduce the biomass of dominant plant species, which resulted in a decrease on aboveground plant biomass and an increase in plant species richness. The little influence of haying on other species may explain the non-significant impact on SOC.