Litter age interacted with N and P addition to impact soil N_(2)O emissions in Cunninghamia lanceolata plantations

凋落物年龄和氮、磷添加交互作用对杉木林土壤N_(2)O排放的影响

Litter decomposition impacts carbon(C)and nutrient cycling.Nitrogen(N)and phosphorus(P)addition as well as litter age impact litter decomposition.Effects of nutrient addition and litter age on litter decomposition may impact emissions of soil nitrous oxide(N_(2)O),which is an important greenhouse gas.However,no study has examined the effects of interactions between litter age and nutrient addition on soil N_(2)O emissions,and explored the underlining mechanisms simultaneously,thus limiting our evaluation of litter decomposition effects on N_(2)O emissions.Litter with different age was collected from Cunninghamia lanceolata plantations experienced N and P addition treatments to examine the effects of nutrient addition and litter age on N_(2)O emissions by incubation study.Litter age generally increased N_(2)O emissions via a decrease in litter C:N ratio.While P addition decreased N_(2)O emissions,N addition increased them mainly by positive effects on soil enzymes as indicated by microbial functional genes associated with N_(2)O production and negative effects on litter C:N ratio.Litter age and nutrient addition interacted to impact soil N_(2)O emissions.In future forest management,both nutrient addition and litter age should be considered in evaluation of management effects on N_(2)O emissions,especially thinning or selectively cutting involving litter input with different age.

氧化亚氮(N_(2)O)是一种重要的温室气体,增温潜势较大,其浓度增加影响全球气候变化。由于凋落物分解影响碳和养分循环,土壤N_(2)O排放受凋落物分解作用,而凋落物年龄和氮、磷添加影响凋落物分解,潜在影响土壤N_(2)O的排放。然而,凋落物年龄和养分添加对土壤N_(2)O排放的交互作用及其机制目前还没有报道,这限制了凋落物分解对N_(2)O排放的影响评价。本研究以杉木(Cunninghamia lanceolata)不同年龄凋落物为研究对象,通过氮、磷添加处理,研究了养分和凋落物年龄对N_(2)O排放的影响及其机制。研究结果显示,幼龄凋落物主要通过调节碳氮比来影响N_(2)O排放。氮添加主要通过调节凋落物碳氮比、土壤pH以及与N_(2)O产生相关的微生物功能基因所编码的土壤酶活性来影响N_(2)O排放,整体上促进N_(2)O排放。磷添加显著降低凋落物碳氮比,进而作用于N_(2)O排放,该途径促进N_(2)O排放。同时,磷添加提高土壤有效磷水平,潜在降低N_(2)O排放,整体上降低土壤N_(2)O排放。凋落物年龄和养分添加交互作用于土壤N_(2)O排放。因此,在森林经营管理中,评价不同管理措施,尤其是间伐和选择性砍伐等导致不同凋落物输入的管理活动对土壤N_(2)O排放的影响时,应同时考虑养分输入和凋落物年龄的潜在影响。