Response of soil nutrients and stoichiometry to grazing management in alpine grassland on the Qinghai-Tibet Plateau

Abstract

Soil nutrients and stoichiometry are two important fertility indicators for grassland ecosystems, and are essential to maintain ecosystem function and protect land from degradation. Although many case studies have been conducted, the effect of grazing management on soil nutrients of alpine grassland is still poorly understood because of the complex nature of grassland soil. In this study, we synthesized the results of 53 peer-reviewed publications and conducted a meta-analysis to explore the effects of grazing on soil nutrient levels. Our results indicated that grazing significantly decreased soil organic carbon (SOC, -13.7 %), soil total nitrogen (TN, -12.7 %), soil total phosphorus (TP, -11.6 %), soil available phosphorus (-7.7 %), soil moisture (SM, -21.1 %) and soil C:N ratio (-3.4 %). In contrast, grazing significantly increased soil bulk density (+16.7 %) and soil temperature (+8.5 %), while it had no effect on soil available nitrogen, or the ratios of C:P and N:P in soil. Specifically, grazing effects on SOC, TN and TP decrease with increasing grazing intensity, but light grazing had no significant effect on them. The response ratio of SOC was significantly positively correlated with the response ratio of TN, SM, C:N and C:P ratios (p < 0.01), suggesting that the mutual influence of soil nutrient variables in alpine grassland under grazing. In addition, the response of soil nutrients to grazing was also affected by grazing season, livestock type and grazing duration. Our study provides new insights into how soil nutrient levels are impacted by different grazing management strategies in alpine grassland ecosystems on the QTP. This information can be form the basis for future studies into sustainable management of alpine grassland.