土壤可溶性有机氮及土壤微生物对其调控的研究进展

摘要

In soil,nitrogen mostly exists in the form of organic polymers,which can transform into soluble organic nitrogen (SON)through a series of complex biological and non-biological processes.In this paper,SON refers to the organic nitrogen extracted by water or salt solution,rather than the dissolved organic nitrogen (DON)collected in situ .Currently,the research on SON largely focuses on forest-,grassland-and/or agro-ecosystems.There are differences in the content and composition of the soil SON in different ecosystems that vary in soil type,land use, vegetation,soil management and/or environmental factors.A great deal of the information obtained thus far indicates a correlation between SON content and the quantities and components of the microorganisms in soil,the activities of extracellular enzymes,etc.The transformation process may include breakdown of the polymeric nitrogen by bacteria,fungi and/or extracellular depolymerases secreted by microbes in soilor plants into soluble subunits that can be utilized by microorganisms or plants.The soluble subunits may also be further degraded into ammonium (NH +4 )and nitrate (NO-3 ),which are the preferred N source for bacteria,fungi and plants.At present,few study targets the microbes that are capable of degrading organic nitrogen into subunits,while only a few reported the degradation and absorption of organic nitrogen by mycorrhizal fungi.Thus,future studies ought to be directed toward the understanding of the regulatory mechanisms of soil organic nitrogen transformation.%有机氮是土壤氮素的主要存在形式，土壤中有机氮大多以聚合物形式存在，经过一系列复杂的生物和非生物过程转变成可溶性有机氮。本文总结了不同生态系统可溶性有机氮的研究现状，指出当前可溶性有机氮的研究主要集中在森林生态系统、草地生态系统和农业生态系统，在不同的生态系统中，由于土壤类型、土地利用类型、覆盖的植被类型、土壤管理措施和环境因素等的不同，土壤可溶性有机氮的含量和组分均存在差异。本文还综述了当前可溶性有机氮生物转化过程的研究现状，指出可溶性有机氮含量与土壤微生物的数量、组分及胞外酶的活性有关，其生物转化过程为：在土壤微生物（细菌、真菌等）及胞外解聚酶如蛋白酶、几丁质酶等的作用下，大分子有机氮降解为小分子有机氮，被植物和微生物直接吸收利用，或进一步降解为 NH ＋4和NO－3被植物和微生物吸收利用。认为未来应该加强土壤有机氮转化代谢过程的调控机制研究。