Faculty of Natural Resources Management, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B 5E1, Canada.
Faculty of Natural Resources Management, Lakehead University, 955 Oliver Road, Thunder Bay, Ontario P7B 5E1, Canada.
Sci Total Environ. 2023 May 1;871:161986. doi: 10.1016/j.scitotenv.2023.161986. Epub 2023 Feb 6.
Soil respiration (R) is a key indicator of belowground biological activities of terrestrial ecosystems. Despite ongoing atmospheric nitrogen (N) deposition due to anthropogenic activities, it remains uncertain how R responds to globally varied atmospheric N deposition. Based on a meta-analysis of 340 simulated experimental nitrogen addition studies, we aimed to identify the key factors altering the responses of R to N deposition and extrapolate these results to the global mapping of R changes under N deposition. We found the overall experimental N addition effect on R was insignificant, but the responses of R significantly shifted from positive to negative with increasing accumulated N addition amount and lower soil pH, and the negative responses to increasing N amounts were significantly intensified in acid soils. Also, the response of heterotrophic respiration to N addition significantly increased with a lower N amount, and both responses of heterotrophic and autotrophic respiration were significantly more negative in soils with lower pH. Our mapping efforts showed that global R overall increased by 2.8 % in response to the accumulated N deposition from 2000 to 2020. Regions with combined characteristics of high accumulated N deposition amounts and low soil pH, including Eastern U.S., Europe, and Eastern Asia, were hotspots of R declines under current and future atmospheric N deposition. Our findings challenge the long-held notion that N deposition has universal negative impacts on R, and suggest the spatial heterogeneity in the impacts of N deposition on belowground activities and carbon release across the globe.
土壤呼吸（R）是陆地生态系统地下生物活动的关键指标。尽管由于人为活动导致大气氮（N）不断沉积，但仍不确定 R 对全球不同大气 N 沉积的响应如何。基于对 340 项模拟氮添加实验的荟萃分析，我们旨在确定改变 R 对 N 沉积响应的关键因素，并将这些结果外推到全球 N 沉积下 R 变化的映射。我们发现，总体而言，实验性 N 添加对 R 的影响并不显著，但随着累积 N 添加量的增加和土壤 pH 值的降低，R 的响应明显从正转负，并且在酸性土壤中，对 N 增加量的负响应显著加剧。此外，异养呼吸对 N 添加的响应随着 N 量的减少而显著增加，而在 pH 值较低的土壤中，异养和自养呼吸的响应都明显更为负面。我们的制图工作表明，全球 R 整体上在 2000 年至 2020 年期间因累积 N 沉积增加了 2.8%。具有高累积 N 沉积量和低土壤 pH 值综合特征的地区，包括美国东部、欧洲和东亚，是当前和未来大气 N 沉积下 R 下降的热点地区。我们的研究结果挑战了氮沉积对 R 普遍具有负面影响的长期观点，并表明全球范围内 N 沉积对地下活动和碳释放的影响存在空间异质性。
