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.