模拟氮沉降对滇中高山栎林凋落物碳氮磷释放和生态化学计量特征的影响

Effects of simulated nitrogen deposition on C,N and P release from litter and ecological stoichiometry in Quercus aquifolioides forest in central Yunnan

【目的】研究氮(N)沉降下森林凋落物分解过程中碳氮磷释放和化学计量特征响应情况,为揭示亚热带高海拔区域森林生态系统在未来大气N沉降的影响下养分循环的变化趋势提供参考。【方法】以滇中亚高山高山栎林(Quercus aquifolioides)为研究对象,利用尼龙网袋法于2018年2月至2019年1月开展模拟N沉降下高山栎林凋落叶、凋落枝原位分解试验,设置4个N沉降处理水平,分别为对照(CK,N 0 g/(m^(2)·a))、低氮(LN,N 5 g/(m^(2)·a))、中氮(MN,N 15 g/(m^(2)·a))和高氮(HN,N 30 g/(m^(2)·a))。测定不同处理凋落叶、凋落枝C、N、P残留率的变化,并分析N沉降1年后凋落叶、凋落枝及土壤中C、N、P含量以及C/N、C/P、N/P的变化,最后采用相关性分析和冗余分析对凋落叶、凋落枝和土壤C、N、P及其化学计量比的相关性进行分析。【结果】N沉降下,凋落叶、凋落枝的C、N、P释放模式分别为直接释放、富集-释放、缓慢释放,凋落叶C、N、P释放速率较凋落枝快。N沉降抑制了凋落物(叶、枝)中C、N、P的释放,与CK相比,N沉降1年后,凋落物C、N、P残留率分别增加了1.70%~10.15%,8.45%~23.96%,3.11%~15.78%。N沉降1年后,与CK相比,N沉降处理均增加了凋落物(叶、枝)和土壤中C、N、P含量,且对凋落物(叶、枝)C、N影响达显著水平;N沉降均降低了凋落物和土壤中C/N、C/P值,且对凋落物C/N影响达显著水平。相关性分析和冗余分析结果表明,N沉降下,凋落叶和凋落枝C、N、P含量均与土壤中N、P含量相关性达显著或极显著水平;土壤P对凋落物化学计量的影响较大,土壤N次之,土壤C则影响最小。【结论】在大气N沉降的背景下,滇中区域高山栎林凋落物分解过程中C、N、P养分释放受到了抑制,土壤中的N、P含量对凋落物分解过程中的化学计量变化特征及养分释放具有重要作用。

【Objective】This research investigated the response of carbon(C),nitrogen(N)and phosphorus(P)release and ecological stoichiometry of forest litter decomposition under N deposition to provide references for revealing the trend of nutrient cycling of forest ecosystems in subtropical high-altitude area under the influence of atmospheric N deposition in the future.【Method】From February 2018 to January 2019,simulated N deposition experiments were conducted in the subalpine of Quercus aquifolioides forest in central Yunnan.The litter bag method was used to carry out in-situ decomposition experiment of two kinds of litter(leaf and twig).Four treatment levels of N deposition were applied including control check(CK,N 0 g/(m^(2)·a)),low nitrogen(LN,N 5 g/(m^(2)·a)),medium nitrogen(MN,N 15 g/(m^(2)·a))and high nitrogen(HN,N 30 g/(m^(2)·a)).The residual rates of C,N and P of leaf and twig litter under diffe-rent N treatments were measured,the changes of C,N and P contents and C/N,C/P and N/P ratios of leaf and twig litter and soil after one year treatment were determined,and the correlations of C,N,P and stoichiometric ratios of leaf and twig litter and soil were analyzed by canonical correlation analysis and redundancy analysis.【Result】Under N deposition,the release patterns of C,N and P in litter(leaf and twig)were direct release,accumulation release,and slow release,respectively.Leaf litter release was faster than twig litter.N deposition inhibited the releases of C,N and P elements in litters.After one year treatment,the residual rates of C,N and P in litter were increased by 1.70%to 10.15%,8.45%to 23.96%and 3.11%to 15.78%,respectively.Compared with CK,N deposition increased C,N and P contents of litter(leaf and twig)and soil with significant changes in litter C and N.N deposition reduced C/N and C/P of litter and soil,and C/N changes reached significant level.Correlation analysis and redundancy analysis showed that the C,N and P contents of litter(leaf and twig)were closely related to N and P contents of soil under N deposition.Soil P significantly affected litter stoichiometry,followed by soil N and soil C.【Conclusion】With atmospheric N deposition,the releases of C,N and P in the decomposition process of Quercus aquifolioides litter in central Yunnan were inhibited,and N and P contents in soil played an important role to ecological stoichiometry and nutrient release from litter decomposition.