Precipitation and species composition primarily determine the diversity-productivity relationship of alpine grasslands on the Northern Tibetan Plateau

摘要

Understanding the biodiversity-productivity relationship is essential for sustainable pasture management. We performed a multi-site transect survey across three alpine grassland types, meadow, steppe and desert steppe to get some initial insights into how biotic and abiotic factors drive both aboveground net primary productivity (ANPP) and species richness (SR). We first explored the SR-ANPP relationship at different scales, then examined the relationship between diversity, productivity and environmental factors, and finally decomposed the relative contribution of each term to observed variations by analyses of covariance with .general linear models (GLMs). The unimodal pattern, with lower corrected Ak-aike information criterion values, was found slightly better fitted than the positive linear one within steppe and across all three grassland types, whereas no obvious relationship was observed in meadow or desert steppe. We evaluated plant functional group composition (FGC), with species scored as 1-xerophytes, 2-mesophytes and 3-hygrophytes. Both ANPP and SR exponentially increased with growing season precipitation (GSP) and logarithmically with FGC. Results from GLMs showed that local species pool (LSP) explained 57.5 % of variation in SR and that FGC had an equal power as GSP in explaining variation in ANPP (about 31 %). Results indicate that the SR-ANPP curve is an aggregate of concurrent relationships across spatial scales and ecological levels. The relationship of the LSP and FGC with precipitation indicated a strong dependence between plants and alpine climate. Therefore, changes in species composition should be seriously considered in alpine vegetation response to potential climate change and anthropogenic disturbance.