Abstract Cultivated grassland can serve as one solution to the degradation of natural grassland. However, less is understood of the response of the microbial communities in cultivated grassland soils to global change factors such as nitrogen (N) deposition and precipitation change, and their linkages with the dynamics of soil organic carbon (SOC). In this study, field experimental plots that simulate different N deposition and precipitation levels were established to investigate the responses of soil microbial communities and their linkages with particulate-sized SOC fractions. Results showed that the activities of hydrolytic enzymes responded significantly to N addition, watering and their combinations, whereas the abundance and composition of microbial communities showed no significant difference among treatments. Addition of N and water generally promoted the activities of N-degrading enzymes such as β-N-acetylglucosaminidase (NAG) and leucine aminopeptidase (LAP), and thus decreased the C- to N-degrading activity (enzyme C/N ratio). This decrease in enzyme C/N ratio was significantly correlated with the accumulation of microbial-accessible particulate organic carbon (POC), indicating that three years of N application did not alleviate microbial N limitation so that microbial communities had invested more in acquisition of N instead of C. In contrast, the content of microbial-inaccessible mineral associated organic carbon (MAOC) was decreased probably as a result of N limitation on the suppressed microbial growth. Collectively, these results highlight that stoichiometric deviation between substrate and microbial demand can be one critical driver for SOC dynamics in cultivated grassland under global change scenarios.

中文翻译：

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酶化学计量学的改变控制着温带栽培草地土壤有机碳动态对氮和水添加的响应

摘要 人工草地可以作为解决天然草地退化的一种方法。然而，人们对栽培草地土壤中微生物群落对氮 (N) 沉积和降水变化等全球变化因素的响应及其与土壤有机碳 (SOC) 动态的联系知之甚少。在这项研究中，建立了模拟不同 N 沉积和降水水平的田间实验地块，以研究土壤微生物群落的响应及其与颗粒大小的 SOC 部分的联系。结果表明，水解酶的活性对施氮、浇水及其组合有显着影响，而微生物群落的丰度和组成在处理之间没有显着差异。N和水的添加通常会促进N-降解酶如β-N-乙酰氨基葡萄糖苷酶（NAG）和亮氨酸氨肽酶（LAP）的活性，从而降低C-N-降解活性（酶C/N比）。酶 C/N 比的这种下降与微生物可及的颗粒有机碳 (POC) 的积累显着相关，表明三年的施氮并未缓解微生物 N 限制，因此微生物群落更多地投资于 N 的获取相比之下，微生物无法接近的矿物伴生有机碳 (MAOC) 的含量可能由于氮限制抑制微生物生长而减少。总的来说，