Patterns and drivers of carbon, nitrogen and phosphorus stoichiometry in Southern China's grasslands

Abstract

Understanding vegetation and soil carbon (C), nitrogen (N) and, phosphorus (P) stoichiometry and its controls are essential for evaluating the biogeochemical cycle and ecosystem functioning. However, the spatial patterns of C, N, and P stoichiometry and their controls for grasslands in southern China are mostly unknown. In this study, we examined the spatial patterns of vegetation and soil C, N, and P concentrations and C:N:P ratios in grasslands of southern China and the underlying environmental factors related to these patterns, based on ~500 field-sampled grasslands. Our results indicated that vegetation and soil N and P concentrations were the highest in temperate mountainous grass-forb meadows (TM), followed by warm grasslands (WG) and warm shrub grasslands (WS), and the lowest in tropical shrub tussock grasslands (TS). In contrast, the vegetation C:N ratio was the highest in TS, followed by WG and WS, and the lowest in TM. C:P ratio in TS was significantly higher than that in TM, but vegetation N:P ratio was not significantly different among grassland types. Soil C:N ratio in WS was significantly higher than that in TS, but its N:P and C:P ratios were not significantly different among grassland types. Redundancy analysis showed that climate was the dominant factor related to vegetation C:N ratio, followed by soil nutrients and the vegetation type. However, the dominant control over C:P ratio was the soil nutrients, followed by climate variables, while vegetation type was of little importance. N:P was found to be only significantly related to soil nutrients. Our results suggested a stoichiometric shift in vegetation C:N:P among different vegetation types, implying that nutrient ratios and biogeochemical cycles in grassland ecosystems can be further affected by vegetation shift under future climate change and anthropogenic activities.