Center for Ecological and Environmental Sciences, Northwestern Polytechnical University, Xi'an, 710072, China.
State Key Laboratory of Loess and Quaternary Geology (SKLLQG), Key Laboratory of Aerosol Chemistry and Physics, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, 710061, China.
Glob Chang Biol. 2017 Mar;23(3):1328-1337. doi: 10.1111/gcb.13402. Epub 2016 Jul 28.
Unprecedented levels of nitrogen (N) have been deposited in ecosystems over the past century, which is expected to have cascading effects on microbially mediated soil respiration (SR). Extracellular enzymes play critical roles on the degradation of soil organic matter, and measurements of their activities are potentially useful indicators of SR. The links between soil extracellular enzymatic activities (EEAs) and SR under N addition, however, have not been established. We therefore conducted a meta-analysis from 62 publications to synthesize the responses of soil EEAs and SR to elevated N. Nitrogen addition significantly increased glycosidase activity (GA) by 13.0%, α-1,4-glucosidase (AG) by 19.6%, β-1,4-glucosidase (BG) by 11.1%, β-1,4-xylosidase (BX) by 21.9% and β-D-cellobiosidase (CBH) by 12.6%. Increases in GA were more evident for long duration, high rate, organic and mixed N addition (combination of organic and inorganic N addition), as well as for studies from farmland. The response ratios (RRs) of GA were positively correlated with the SR-RRs, even when evaluated individually for AG, BG, BX and CBH. This positive correlation between GA-RR and SR-RR was maintained for most types of vegetation and soil as well as for different methods of N addition. Our results provide the first evidence that GA is linked to SR under N addition over a range of ecosystems and highlight the need for further studies on the response of other soil EEAs to various global change factors and their implications for ecosystem functions.
过去一个世纪以来，生态系统中氮（N）的沉积水平前所未有，预计这将对微生物介导的土壤呼吸（SR）产生级联效应。细胞外酶在土壤有机质的降解中起着关键作用，其活性的测量可能是 SR 的有用指标。然而，在 N 添加下，土壤细胞外酶活性（EEA）与 SR 之间的联系尚未建立。因此，我们从 62 篇文献中进行了荟萃分析，以综合 EEAs 和 SR 对 N 增加的响应。氮添加显著增加了糖苷酶活性（GA）13.0%，α-1,4-葡萄糖苷酶（AG）19.6%，β-1,4-葡萄糖苷酶（BG）11.1%，β-1,4-木糖苷酶（BX）21.9%和β-D-纤维二糖水解酶（CBH）12.6%。对于长持续时间、高速率、有机和混合 N 添加（有机和无机 N 添加的组合），以及农田研究，GA 的增加更为明显。GA 的响应比（RR）与 SR-RR 呈正相关，即使单独评估 AG、BG、BX 和 CBH 也是如此。GA-RR 和 SR-RR 之间的这种正相关关系在大多数类型的植被和土壤以及不同的 N 添加方法中都得到了维持。我们的研究结果首次提供了证据，表明在一系列生态系统中，GA 在 N 添加下与 SR 有关，并强调需要进一步研究其他土壤 EEAs 对各种全球变化因素的响应及其对生态系统功能的影响。
