氮输入对土壤甲烷产生、氧化和传输过程的影响及其机制

随着人为氮输入的增加,外源氮成为影响土壤甲烷产生、氧化和传输过程的重要因素。土壤甲烷排放受氮素有效性的调节,氮输入会改变土壤初始环境和甲烷排放规律,最终影响甲烷排放量。综述了氮输入对土壤甲烷产生、氧化和传输过程的影响及机制。研究表明,1)氮输入对甲烷排放通量的影响存在促进、抑制和不显著3种情况,这主要是甲烷产生、氧化和传输过程的变化引起的;2)氮输入对甲烷产生过程的影响受产甲烷底物和产甲烷微生物活性的控制,氮输入通过增加土壤有机碳的含量为甲烷产生提供了丰富的底物,同时底物理化性质和植被覆盖度的变化使得这种影响复杂化,氮输入既可促进又可抑制产甲烷菌的活性,并且这种作用受氮形态的影响;3)氮输入对甲烷氧化过程的影响主要是通过刺激或抑制甲烷氧化菌的活性实现的,氮形态的不同也使得这种变化更为复杂;4)氮输入对甲烷传输过程的影响主要受植物通气组织的数量以及传输效率的控制,并且在不同生态系统这种控制作用差异较大。综上所述,氮输入对土壤甲烷产生、氧化和传输过程的影响及机制具有明显的复杂性和不确定性,今后研究中应综合考虑氮输入对甲烷排放关键过程的影响,并侧重于探讨氮输入对相关微生物群落结构、丰度和活性的影响,同时注重对各个生态系统的协同研究,确定氮输入影响下各个生态系统对全球甲烷排放的贡献率。

Effects of nitrogen input on CH4 production,oxidation and transport in soils,and mechanisms:a review

Methane is an important component of carbon output in anaerobic soil.Minor changes to the soil car-bon cycle will cause significant changes in the metabolic processes involving methane,which in turn can be markedly affected by exogenous nitrogen input.With increase in anthropogenic nitrogen inputs,exogenous ni-trogen becomes an important factor in soil methane production,oxidation,and transmission processes.Meth-ane emissions are regulated by nitrogen availability.Nitrogen inputs can change the background environmentand methane emission mechanisms in soil,and consequently influence methane emission fluxes.Research into effects of nitrogen input on CH4 production and the mechanisms of N effects on oxidation and transport proces-ses in soils are reviewed in this paper.The important findings in the literature are:1)The effects of nitrogen input on CH4 fluxes in soils can be positive,negative or neutral,due to the range of effects of added N on methane production,oxidation,and transport processes;2)The effects of nitrogen input on methane produc-tion processes are controlled by methanogenic substrates and methanogenic microbial activities.Nitrogen input provides rich substrates for methane production by increasing soil organic carbon content.The changes in the physical and chemical properties of substrates and vegetation cover make this effect complicated.Nitrogen in-put can also either promote or inhibit the activity of methanogens,depending on the form of nitrogen supplied;3)The effects of nitrogen input on methane oxidation processes mainly arise from stimulation or inhibition of the activities of methanotrophs;4)The effects of nitrogen input on methane transport processes depend mostly on the number of aerenchyma vessels and on transport efficiencies,and the degree of dependence varied greatly in different ecosystems.Overall,the effects of nitrogen input on soil CH4 production,oxidation,and transport process are complicated and the mechanisms are uncertain.Future research should focus on the effects of nitro-gen input on the critical processes determining methane emissions,on investigation of the effects of nitrogen in-put on microbial community structures,abundance and activities,and on collaborative research in a range of e-cosystems.The goal of future research should be to determine the contribution of various ecosystems to global methane emissions at specific levels of nitrogen input.