氮、磷养分有效性对森林凋落物分解的影响研究进展

摘要

通过对相关研究文献的综述结果表明,氮(N)和磷(P)是构成蛋白质和遗传物质的两种重要组成元素,限制森林生产力和其他生态系统过程,对凋落物分解产生深刻影响.大量的凋落物分解试验发现在土壤N有效性较低的温带和北方森林,凋落物分解速率常与底物初始N浓度、木质素/N比等有很好的相关关系,也受外源N输入的影响;而在土壤高度风化的热带亚热带森林生态系统中,P可能是比N更为重要的分解限制因子.然而控制试验表明,N、P添加对凋落物分解速率的影响并不一致,既有促进效应也有抑制效应.为了深入揭示N、P养分有效性对凋落物分解的调控机制,“底物的C、N化学计量学”假说、“微生物的N开采”假说以及养分平衡的理论都常被用于解释凋落物分解速率的变化.由于微生物分解者具有较为稳定的C、N、P等养分需求比例,在不同的养分供应的周围环境中会体现出不同的活性,某种最缺乏的养分可能就是分解的最重要限制因子.未来的凋落物分解研究,应延长实验时间、加强室内和野外不同条件下的N、P等养分添加控制试验,探讨驱动分解进程的微生物群落结构和酶活性的变化.%Nitrogen (N) and phosphorus (P) are the two most important elements for building plant proteins and genetic material,limiting forest production,and other ecosystem processes,and they profoundly affect litter decomposition.Litterquality parameters,particularly initial lignin and N contents,ratios of C ∶N,and lignin:N often correlate strongly with rates of litter mass loss in temperate and boreal forests.Furthermore,soil N availability and N addition also affect litter decomposition.In tropical and subtropical forests,where highly weathered soil is frequently observed,P could be more important than N in inhibiting litter decomposition.However,P has not been considered in most current ecosystem carbon cycling models,but fertilization experiments show different responses of litter decomposition rates to nutrition addition.Synergistic,antagonistic,and neutral effects can be observed.Both the "basic stoichiometric decomposition theory" and "microbial nitrogen mining" hypothesis have been used to explain litter decomposition rate variations with nutrition addition.Regarding rigid C ∶N ∶P ratios in microbial decomposers,different nutrition sources could result in altered microbial activity,and limited nutrient supplies could result in restricted litter decomposition.To clearly understand the effects of N and P regulation on decomposition,we need longer decomposition experiment durations,more intensive field and laboratory fertilization experiments,and simultaneously,microbe and enzyme dynamics in the decomposition process should be further investigated.