土壤有机碳的周转及稳定与氮沉降和凋落物分解密切相关。然而，关于氮沉降驱动下毛竹凋落物分解如何影响土壤不同有机碳组分，还存在较大不确定性。为了探究氮沉降驱动下凋落物分解对土壤有机碳组分的影响，本研究依托浙江农林大学安吉毛竹林氮沉降试验基地，设置氮处理(N，施氮量50 kg N·hm-2·a-1;CK，施等量水对照)和凋落物处理(L，凋落物保留;LR，凋落物去除)，分析了各处理下凋落物分解的质量损失及土壤理化性质、颗粒态有机碳(POC)、矿物结合态有机碳(MAOC)和土壤胞外酶活性(EEAs)。结果表明:施氮处理显著降低了毛竹叶凋落物的质量损失。施氮处理可显著增加POC含量，但显著降低了MAOC含量，而凋落物保留可同时显著增加POC和MAOC含量。施氮处理均显著降低了 β-葡萄糖苷酶(BG)、β-木糖苷酶(BX)、纤维二糖水解酶(CBH)、N-乙酰-β-D氨基葡萄糖苷酶(NAG)、酚氧化酶(POX)和过氧化物酶(PER)活性，而凋落物保留处理显著增加了 BG、POX和PER活性。相关性分析和随机森林分析显示，氮处理下影响毛竹叶凋落物分解的关键因子是BG、PER、pH、微生物生物量碳(MBC)和POX等。冗余分析(RDA)和回归拟合分析表明，POC与凋落物分解的质量损失率、MBC、BG、CBH、POX和PER呈显著负相关，与铵态氮(NH4+-N)和硝态氮(NO3--N)呈显著正相关;而MAOC则与凋落物质量损失率、pH、MBC、CBH、NAG、POX和PER呈显著正相关，与微生物生物量氮(MBN)呈显著负相关。综上，氮沉降主要通过降低有关胞外酶活性抑制毛竹叶凋落物的分解，进而增加土壤POC含量，并减少MAOC含量。
Impact of litter decomposition driven by nitrogen deposition on the soil organic carbon fractions in a Moso bamboo forest
Soil organic carbon turnover and stabilization are closely related to nitrogen deposition and litter decom-position.However,there are great uncertainties about how the decomposition of bamboo litter driven by nitrogen deposition affects soil organic carbon components.To investigate the effects of nitrogen deposition-driven litter decomposition on soil organic carbon components,we conducted an experiment at the Anji Moso bamboo ecosystem research station of Zhejiang A&F University with nitrogen treatments(N,50 kg N·hm-2·a-1;CK,control with equal amount of water)and litter treatments(L,litter retention;LR,litter removal)to analyze changes in litter mass loss,soil physicochemical properties,particulate organic carbon(POC),mineral-associated organic carbon(MAOC),and soil extracellular enzyme activity(EEAs).The results showed that nitrogen application significantly reduced the mass loss of leaf litter.Nitrogen application significantly increased POC content and decreased MAOC content,but litter retention significantly increased the contents of POC and MAOC in soil.Nitrogen application sig-nificantly decreased the activities of β-1,4-glucosidase(BG),β-1,4-xylosidase(BX),cellobiohydrolase(CBH),β-1,4-N-acetyl-glucosaminnidase(NAG),phenol oxidase(POX),and peroxidase(PER),while litter retention significantly increased the activities of BG,POX,and PER.Results of correlation analysis and random forest analysis showed that the key factors affecting the decomposition of Moso bamboo litter under nitrogen treat-ment were BG,PER,pH,microbial biomass carbon(MBC)and POX.Through redundancy analysis(RDA)and regression fitting analysis,we found that POC was significantly negatively correlated with mass loss,MBC,BG,CBH,POX and PER,and significantly positively correlated with ammonium nitrogen(NH4+-N)and nitrate nitro-gen(NO3--N).MAOC was significantly positively correlated with mass loss,pH,MBC,CBH,NAG,POX and PER,and negatively correlated with microbial biomass nitrogen(MBN).In conclusion,nitrogen deposition inhibits bamboo leaf litter decomposition by reducing extracellular enzyme activities,thereby increasing soil POC content and decreasing MAOC content.
万方数据
维普
