Increased in local precipitation weakenes long-term responses of soil carbon and nitrogen to climate change: Insights from a 37-year experiment

Abstract

Soil ecological stoichiometry play vital roles in regulating structure and function of grassland ecosystems. However, the long-term dynamics of soil nutrient elements and their underlying driving mechanisms remain poorly understood, particularly in the context of changing precipitation patterns. Here, we conducted a long-term experiment to assess temporal-spatial dynamics and mechanisms of soil ecological stoichiometry along the precipitation gradient. Over the past 37 years, our results indicated a significant overall increase in soil organic carbon (SOC) and total nitrogen (STN) contents, accompanied by a decrease in soil total phosphorus (STP) content across the three sites. The sensitivity of SOC, STN, C:P, and N:P to climate change decreased significantly as local precipitation increased, while the sensitivity of SOC, STN, and C:N to local precipitation declined significantly over time. From north to south, STP content increased on average by 1.03 %, 1.16 % and 1.68 % in 1985, 2002 and 2022, respectively. Additionally, the coupling strength of SOC, STN and STP decreased with increasing local precipitation from 1985 to 2002. Furthermore, the interaction between climate and soil properties explained 18 % and 22 % of the variation in temporal stability and contents of SOC, STN and STP, climate was the most critical factor affecting spatial stability of SOC, STN and STP. Among them, average precipitation, plant phylogenetic diversity and soil moisture were key indicators of temporal-spatial variability in soil C:N:P stoichiometry. Our findings provide an overview of biogeographical nutrient cycles under different temporal and spatial contexts, which is critical for grassland management and conservation in future global change scenarios.