Soil development mediates precipitation control on plant productivity and diversity in alpine grasslands

The relationship between plant productivity and diversity is central to understanding changes in ecosystem functions. However, this relationship remains controversial due to vegetation types and environmental differences. For example, understanding how soil development involving mineral weathering and pedogenic development processes shapes plant productivity and diversity remains limited, especially in alpine grasslands. Here, we evaluated how plant species richness (SR) and aboveground biomass (AGB) are related to one another, and their drivers, by conducting investigations in 169 alpine grassland sites along a 3000 km-transect in the Qinghai-Tibet Plateau. We found that AGB and SR both exhibited a positive and concave–down relationship. The mean annual precipitation explained 23% of the variance in Vegetation characteristics, followed by altitude (14%), soil N content (13%), soil cation exchange capacity (11%), K content (7%), P content (6%), weathering index of Parker (5%). Precipitation was correlated with AGB and SR, but temperature was not. Drought conditions led to slow soil development with high soil pH, and a lack of soil fertility and water jointly limited plant productivity. Our results demonstrate that conservation of diversity within vulnerable ecosystems is critical to maintaining the proper functioning of grassland systems, especially in areas where drought and low soil development are a problem. Soil weathering degree should be considered in efforts seeking to improve projections of alpine grassland ecosystem functioning under future climate change.