Contrasting elevational patterns of microbial carbon and nutrient limitation in soil from alpine meadow to desert

Abstract

The understanding of soil microbial resource limitation has important implications for belowground nutrient cycling. Climate is a primary factor that regulates microbial resource limitation directly and indirectly. Elevational gradient has been used as a substitution of latitudinal gradient in ecological studies because the former displays a wide range of climate variation as the latter. However, whether the elevational trend of microbial resource limitation follows that of latitudinal pattern is still not well known. Here we aimed to 1) test the elevational patterns (465–3035 m a.s.l.) of microbial carbon (C) and nutrient (P: N) limitations in the Tianshan Mountain by using the enzymatic vector analysis, and 2) examine the importance of microclimate and soil resource in regulating microbial C and P:N limitation along the elevational gradient. We found that microbial C limitation generally decreased and microbial P:N limitation increased with increasing elevation, which were the opposite to those of latitudinal patterns. Our results further indicated that microbial C limitation was primarily controlled by soil microclimate with soil moisture alleviating microbial C limitation in the warm & dry climatic condition (465–1240 m a.s.l.) but intensifying in the cold & wet climatic condition (1400–3035 m a.s.l.). Microbial P:N limitation was mainly regulated by soil available P and by the shared effects of soil microclimate and resource. Moreover, microbial C limitation was negatively correlated with microbial P:N limitation, which implied that soil C and nutrient supplies were strongly coupled. Overall, the spatial changes of microbial resource limitation cannot be simply inferred from latitude to altitude or vice versa, instead we should focus on how the determinants of microbial resource limitation change along these environmental gradients.