School of Forestry and Landscape Architecture, Anhui Agricultural University, Hefei 230036, China; Huitong Experimental Station of Forest Ecology, CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Shenyang 110016, China.
Huitong Experimental Station of Forest Ecology, CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Shenyang 110016, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Total Environ. 2022 Nov 15;847:157645. doi: 10.1016/j.scitotenv.2022.157645. Epub 2022 Jul 28.
Influenced by nitrogen (N) deposition, changes in soil organic carbon (SOC) sequestration in terrestrial ecosystems could provide strong feedback to climate change. Mounting evidence showed that microbial necromass contributes substantially to SOC sequestration; however, how N deposition influences microbial necromass accumulation in soils remains elusive. We investigated the impacts of N deposition on soil microbial necromass, assessed by amino sugars, at seven forest sites along a north-south transect in eastern China. We found that the responses of fungal and bacterial necromass accumulation to N deposition depended on the deposition rate, with high N deposition (>50 kg N ha yr) stimulating fungal necromass accumulation from 29.1 % to 35.2 %, while low N deposition damaging the accumulation of bacterial necromass in soil by 12.1 %. On the whole, N deposition benefitted the dominance of fungal over bacterial necromass, with their ratio being significantly greater at high-N level. The accumulation of microbial necromass was primarily governed by soil properties, including nutrients stoichiometry, clay content and pH, while the composition of microbial necromass was conjointly affected by soil properties and microbial community structure. The latitudinal distribution of microbial necromass contributions to SOC pool was not altered by N deposition, and was firmly controlled by the climatic and edaphic factors. Collectively, our results reveal the impacts of N deposition on microbial necromass accumulation in soil and the geographical pattern across forest ecosystems in eastern China, providing implications for our accurate predictions of global change impacts on SOC sequestration.
受氮（N）沉降的影响，陆地生态系统中土壤有机碳（SOC）固存的变化可能会对气候变化产生强烈反馈。越来越多的证据表明，微生物残体对 SOC 固存有重要贡献；然而，N 沉降如何影响土壤中微生物残体的积累仍不清楚。我们在中国东部沿南北方向的 7 个森林地点调查了 N 沉降对土壤微生物残体（通过氨基糖评估）的影响。我们发现，真菌和细菌残体量对 N 沉降的响应取决于沉积速率，高 N 沉降（>50 kg N ha yr）刺激真菌残体量从 29.1%增加到 35.2%，而低 N 沉降则使土壤中细菌残体量减少 12.1%。总的来说，N 沉降有利于真菌残体对细菌残体的优势，在高 N 水平下，其比例显著增加。微生物残体的积累主要受土壤特性控制，包括养分化学计量、粘粒含量和 pH 值，而微生物残体的组成则同时受到土壤特性和微生物群落结构的影响。N 沉降并没有改变微生物残体对 SOC 库的贡献的纬度分布，而是由气候和土壤因素牢固控制。总的来说，我们的结果揭示了 N 沉降对土壤中微生物残体积累的影响以及中国东部森林生态系统的地理模式，为我们准确预测全球变化对 SOC 固存的影响提供了依据。
