Geographical patterns and drivers of plant productivity and species diversity in the Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau (QTP) has three main grassland types: alpine meadow, alpine steppe, and alpine desert steppe. In this study, we asked how plant productivity and species diversity vary with altitude, longitude and latitude in alpine grasslands of the QTP. We then identified the environmental factors that drive these observed patterns of plant productivity and species diversity. We found that although plant productivity and species diversity varied greatly across large-scale longitudinal and latitudinal gradients, these changes were strongest across the longitudinal gradient. This finding indicates that moisture rather than temperature has the greatest impact on plant productivity and species diversity of the alpine grasslands in the QTP. We also found that besides soil and climate factors, partial pressure of carbon dioxide (pCO2) also has significant effects on plant productivity, and barometric pressure and partial pressure of oxygen (pO2) also have significant effects on species diversity. Furthermore, the relationship between the biomass of grassland-dominant species and species diversity was affected by the spatial scale at which these factors were studied. Our study provides new insights into the interconnections between plant productivity and species diversity and the major factors that influence alpine grasslands. It also provides a scientific basis for the maintenance of plant diversity and ecosystem functions in hypoxic (low-oxygen) regions.