Response of plant species richness and ecosystem functioning to aridity and land-use
Plant species richness, aboveground biomass, and SOC decreased with increasing aridity (Table 1, Figs. 1, 2). Grazing reduced plant species richness, aboveground biomass, and SOC (Fig. 2), and the negative effects on species richness and SOC were greater at dry sites (aridity × grazing interaction effect in Table 1). Haying increased species richness and reduced aboveground biomass, but did not affect SOC (Fig. 2). Haying had a greater negative effect on aboveground biomass at dry sites (aridity × haying interaction effect in Table 1).
Plant species richness was positively associated with aboveground biomass and SOC, and this relationship became stronger with increasing aridity (Fig. 3 and the aridity × species richness interaction effect on aboveground biomass in Table 1). The slopes of the relationships between plant species richness and aboveground biomass as well as SOC along the aridity gradients showed that species richness had a greater effect on SOC than on aboveground biomass, and both effects increased with increasing aridity.