Correlations of species diversity and biomass with environmental factors in alpine grasslands across the Qingzang Plateau

To clarify the correlations of productivity and species diversity with critical environment factors in alpine grasslands, we conducted a field survey of the vegetation community structure, soil factors, and climate indicators at 115 sites across alpine grasslands. The differences and relationships between aboveground productivity and species diversity in alpine meadows and steppes were evaluated using one-way analysis of variance, linear regression analysis, and structural equation modeling. The results were as follows: 1) there was a remarkable positive response of aboveground productivity to species diversity (P < 0.05), with a significant difference between alpine meadows and steppes (P < 0.05). 2) Annual mean precipitation significantly affected the aboveground productivity and species diversity (P < 0.05). Aboveground productivity was significantly positively correlated with soil organic carbon, soil available nitrogen, and soil available phosphorus (P < 0.01), whereas species diversity (Shannon-Wiener index) was positively correlated with only soil water content (P < 0.05). However, soil organic carbon and soil available nitrogen significantly affected aboveground productivity and species diversity (P < 0.01), and there were no significant correlations among soil water content, soil available phosphorus, aboveground productivity, and species diversity (P > 0.05). 3) Structural equation modeling analysis indicated that the annual mean precipitation explained 55.8% and 60.3% of the variations in species diversity in alpine meadows and steppes, respectively. In addition, species diversity explained 51.3% and 30.2% of the variations in aboveground productivity in alpine meadows and alpine steppes, respectively. Soil nutrients may constrain the increase in productivity in alpine grasslands. Moisture may dominate spatial patterns and critical ecological processes of species diversity and aboveground productivity in alpine grasslands. Our results provided documents and theoretical references for alpine grasslands to cope with future climate warming and humid trends across the Qingzang Plateau.