Drivers of soil carbon and nitrogen stock in topsoil and deep soil under grazing in two steppe ecosystems

文献类型： 外文期刊

第一作者： Sun, Jiali

作者： Sun, Jiali;Tian, Shichao;Bai, Haihua;Sun, Jiali;Tian, Shichao;Bai, Haihua;Sun, Jiali;Tian, Shichao;Bai, Haihua;Li, Fei;Li, Fei;Li, Fei

作者机构：

关键词： Soil organic carbon stock; Total nitrogen stock; Soil enzyme; Soil microbial; Meadow and typical steppe; Deep soil

期刊名称：ECOLOGICAL INDICATORS （ 影响因子：7.4； 五年影响因子：7.2 ）

ISSN： 1470-160X

年卷期： 2025 年 177 卷

页码：

收录情况： SCI

摘要： Grazing is recognized as a major driver of changes in soil nutrient levels in steppe ecosystems. However, our understanding of the mechanisms underlying grazing-induced changes in deep soil organic carbon (SOC) stocks, total nitrogen (TN) stocks, soil enzyme activities, and microbial remains limited. In this study, we investigated the effects of grazing and steppe type on the SOC and TN concentrations, stocks, enzyme activities, and microbes in the top 1-meter soil layer of semi-arid steppe in Inner Mongolia. The results showed that grazing significantly reduced SOC and TN stocks in the 0-30 cm soil layer of the meadow steppe but significantly increased SOC and TN stocks in the 70-100 cm soil layer of both meadow and typical steppes. With increasing soil depth, SOC and TN stocks, microbial abundance, and enzyme activities consistently decreased. Pearson correlation analysis showed that beta-glucosidase (BG), leucine aminopeptidase (LAP), alkaline phosphatase (ALP), bacterial abundance, and Chao 1 index in the top 30 cm soil layer were significantly and positively correlated with SOC and TN stocks, regardless of grazing. However, this correlation weakened or disappeared in soils deeper than 70 cm in meadow steppes. In typical steppes, the correlation between SOC stock and N-acetylglucosaminidase (NAG), LAP, and ALP was stronger in topsoil than in deeper soils under grazing treatment. Conversely, the correlation between SOC stocks, TN stocks, microbial abundance, and community composition was weaker in deep soil than in topsoil under fenced treatment. Random forest models also indicated that BG, NAG, LAP, ALP, and bacterial and fungal abundances were the most significant predictors of SOC and TN stocks. Overall, SOC and TN stocks are primarily influenced by soil enzyme activities and the abundance and structure of bacterial and fungal communities. Also, the results of this study enhance our understanding of soil carbon and nitrogen stocks, enzyme activities, and microbial dynamics under grazing conditions, thereby contributing to a deeper understanding of soil nutrient dynamics in steppe ecosystems.

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