氮添加对森林土壤有机碳库固存及CO2排放的影响研究进展

氮添加会引起土壤理化性质和养分有效性的改变。受此影响,森林植物的地上碳同化能力和地下碳分配格局也会相应地发生变化,总体表现为促进植物生长固碳,增加凋落物和植物根系沉积碳输入土壤,并改变上述植物源有机质的数量和化学成分。与此同时,土壤微生物的群落结构和生态功能也会受到氮添加的影响,由于土壤中的有机碳分解、转化和稳定等过程均受到微生物的驱动,因此,氮添加所引起的底物供应差异和微生物响应会影响森林土壤有机碳的矿化,并最终影响森林土壤有机碳库固存、稳定和CO₂排放。但目前关于氮添加对森林土壤有机碳库固存能力和CO₂排放特征的影响机制仍不清楚,为此,以森林土壤的碳循环过程为线索,综述了氮添加对底物供应、土壤有机碳激发效应、微生物碳代谢等过程的影响,并尝试梳理在氮添加影响下森林土壤有机碳分解、转化和稳定的微生物驱动机制。这有助于预测氮添加对森林土壤"氮促碳汇"的实际效果,以便研究人员在未来氮沉降日益严重背景下更好地预测森林土壤的碳循环特征,寻找提高森林土壤有机碳库固存能力和降低CO₂排放相关途径提供参考。同时,还分析了目前相关研究中存在的问题,并对该领域未来的研究热点进行了展望。

Effects of nitrogen addition on the organic carbon sequestration and CO2 emissions in forest soils: a review

Nitrogen addition causes changes in soil physicochemical properties and nutrient effectiveness. As a result, the carbon assimilation capacity of forest plants and the belowground carbon allocation patterns also change accordingly, generally promoting the growth of woody plants and increasing the input of carbon from litter and plant roots into the soil. This alteration in plant-derived organic matter quantity and chemical composition occurs in response to nitrogen addition. At the same time, the community structure and ecological functions of soil microorganisms are also influenced by nitrogen addition. Since the processes such as organic carbon decomposition, transformation, and stabilization in soil are driven by microorganisms, the differences in substrate supply and microbial response caused by nitrogen addition will affect the mineralization of organic carbon in forest soils, and ultimately affect the canbon sequestration and stabilization, and CO₂ emission from forest soil organic carbon pools. However, the influencing mechanism of nitrogen addition impact on the sequestration capacity and CO₂ emission characteristics of forest soil organic carbon pools is still unclear. Therefore, this paper takes the carbon cycle process of forest soils as a clue and reviews the effects of nitrogen addition on the processes of substrate supply, soil organic carbon excitation effect, and microbial carbon metabolism. We try to sort out the microbial-driven mechanism of organic carbon decomposition, transformation, and stabilization in forest soils under the influence of nitrogen addition. The results will help predict the actual effects of nitrogen addition on the carbon sequestration capacity caused by nitrogen addition in forest soils, in order to better predict the characteristics of forest soil carbon cycle in the context of increasing nitrogen deposition in the future. It provides a reference for improving the sequestration capacity of forest soil organic carbon pools and reducing CO₂ emissions. At the same time, problems and shortcomings existing in the current research are analyzed and prospects for future research hotspots in this field are provided.