森林土壤氧化亚氮排放对氮输入的响应研究进展

A Review of Responses of Soil Nitrous Oxide Emissions to Nitrogen Input in Forest Ecosystems

大气中氧化亚氮(N_(2)O)浓度的上升加剧了全球变暖。森林土壤在调节大气N_(2)O浓度中发挥着至关重要的作用。近年来,氮(N)输入对森林土壤N_(2)O通量的影响备受关注。然而,森林土壤N_(2)O排放对N输入响应的机制,尤其是植物和微生物对N_(2)O通量的调控作用尚缺乏系统研究。因此,本文综述了N输入如何通过森林植被(根系N吸收、凋落物分解和形成丛枝菌根)和土壤微生物(微生物生物量和群落组成)调控N_(2)O产生途径,从而影响森林土壤N_(2)O排放。结果表明,植物的竞争性氮吸收能降低氮输入对N_(2)O排放的促进作用,其作用大小可能主要取决于土壤“氮饱和”状态。植物凋落物主要通过分解过程中的养分归还和次生代谢产物释放来影响氮输入背景下的森林土壤N_(2)O排放,前者具有促进作用,而后者具有抑制作用。丛枝菌根主要通过吸收有效氮和水分、促进团聚体形成以及改变N_(2)O相关功能基因群落调控森林土壤N_(2)O通量。N输入导致的土壤酸化或养分限制,通常会降低微生物生物量和/或改变微生物群落组成,从而控制N_(2)O排放。N输入对N_(2)O不同产生途径也会造成影响,受土壤湿度、N_(2)O底物浓度以及N_(2)O相关功能基因丰度(AOB、AOA、nirK、nirS和nosZ)的调控。未来在模型预测中,需要将植物氮吸收、凋落物分解、菌根以及N_(2)O产生途径充分纳入模型,以提高模型预测准确性,为全球变化背景下制订森林管理政策和温室气体减排措施提供支持。

Rising nitrous oxide(N_(2)O)concentrations in the atmosphere have exacerbated global warming.Forest soil plays a vital role in regulating atmospheric N_(2)O concentration.The effect of nitrogen(N)input on the N_(2)O fluxes of forest soil has attracted much attention.However,the response mechanism of forest soil N_(2)O emissions to N input,especially the regulatory effects of plants and microorganisms on N_(2)O flux,has not been systematically studied.Therefore,this article reviews how N input affects forest soil N_(2)O emissions through forest vegetation(root N absorption,litter decomposition,and formation of arbuscular mycorrhizal)and soil microorganisms(microbial biomass and community composition).The results show that the competitive N uptake of plants can reduce the promotion of N input on N_(2)O emissions.Importantly,the magnitude of its effect may mainly depend on the state of the soil“N saturation”.Plant litter mainly affects N_(2)O emissions of forest soil under the background of N input through nutrient return and the release of secondary metabolites during the decomposition process.The former has a promoting effect and the latter has an inhibitory effect.The arbuscular mycorrhiza mainly regulates forest soil N_(2)O fluxes by absorbing available N and water,promoting the formation of aggregates,and changing the N_(2)O-related functional gene community.Nitrogen input leads to soil acidification or nutrient limitation,which can reduce microbial biomass and/or influence the composition of microbial communities,and then affects N_(2)O emissions.Nitrogen input also affects different production pathways of N_(2)O,which is regulated by soil moisture,the concentration of N_(2)O substrates,and the abundance of functional genes associated with soil N_(2)O emissions(AOB、AOA、nirK、nirS and nosZ).In the future model predictions,plant N absorption,litter decomposition,mycorrhiza and N_(2)O production pathways can be fully incorporated into the model to improve the accuracy of model predictions,and provide a scientific basis for formulating forest management policies and greenhouse gas abatement measures under the background of global change.