Effects of Nitrogen and Water Addition on Ecosystem Carbon Fluxes in a Grazing Desert Steppe

文献类型： 外文期刊

第一作者： Wen, Chao

作者： Wen, Chao;Shan, Yumei;Yang, Ding;Mu, Lan;Zhang, Pujin;Liu, Xinchao;Chang, Hong;Ye, Ruhan;Huang, Jianhui;Huang, Jianhui

作者机构：

关键词： desert steppe; grazing intensity; precipitation increase; nitrogen addition; net ecosystem CO2 exchange

期刊名称：AGRONOMY-BASEL （ 影响因子：3.4； 五年影响因子：3.8 ）

ISSN：

年卷期： 2025 年 15 卷 8 期

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收录情况： SCI

摘要： Desert steppe ecosystems, characterized by water limitation and high sensitivity to global climate change and anthropogenic disturbance drivers, experience profound alterations in carbon (C) cycling processes driven by the multiplicative interactions among grassland grazing, altered precipitation regimes, and elevated atmospheric nitrogen deposition. However, how historical grazing legacies modulate ecosystem responses to concurrent changes in nitrogen deposition and precipitation regimes remains poorly resolved. To address this, we conducted a field experiment manipulating water and nitrogen addition across grazing intensities (no grazing, light grazing, moderate grazing, heavy grazing) in a Stipa breviflora desert steppe. Over three consecutive growing seasons (2015-2017), we continuously monitored net ecosystem CO2 exchange (NEE), ecosystem respiration (ER), and gross ecosystem production (GEP) to quantify ecosystem CO2 fluxes under these interacting global change drivers. Results revealed that water and nitrogen addition did not alter seasonal CO2 flux dynamics across grazing intensities. Light grazing enhanced ecosystem C sink capacity, whereas heavy grazing reduced NEE and GEP, diminishing C sink strength. Water addition significantly increased CO2 fluxes, strongly correlated with soil moisture. Nitrogen addition exerted a weak C source effect in a water-deficient year but enhanced the C sink in a water-rich year. Nitrogen plus water addition significantly boosted C sink potential, though this effect diminished along the grazing pressure gradient. Our findings demonstrate that the impacts of climate change on soil C fluxes in desert steppes are mediated by historical grazing intensity. Future manipulative experiments should explicitly incorporate grazing legacy effects, and integrate this factor into C models to generate reliable predictions of grassland C dynamics under global change scenarios.

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