滇中常绿阔叶林凋落物养分释放及生态化学计量特征对模拟N沉降的响应

为研究N沉降下凋落物养分释放及生态化学计量特征,以滇中磨盘山常绿阔叶林为研究对象,利用尼龙网袋法布设凋落物(凋落叶、凋落枝)原位分解试验,设置不同施N处理:对照(CK,0 g N·m^-2·a^-1)、低氮(LN,5 g N·m^-2·a^-1)、中氮(MN,15 g N·m^-2·a^-1)和高氮(HN,30 g N·m^-2·a^-1)。结果表明: 模拟N沉降1年后,凋落叶、凋落枝和土壤的C、N含量均表现为随着N沉降量的增加而逐渐升高,增幅分别为0.3%～8.2%、4.9%～69.0%;C/N则表现为随着N沉降量的增加逐渐降低,降幅为0.8%～37.8%;凋落枝P含量、C/P、N/P在各处理下差异均不显著。处理时间与施N水平均显著影响凋落叶、凋落枝及土壤的N、P含量及C/N、C/P、N/P;1年分解过程中,凋落物C、N、P残留率依次呈释放、淋溶-富集-释放、淋溶-富集的模式,外源N显著抑制了凋落物C、N、P释放过程;土壤C、P含量与凋落物N、P含量呈显著正相关,土壤N含量与凋落物C、N含量呈显著正相关。N沉降下常绿阔叶林凋落物与土壤生态化学计量具有显著相关性,研究滇中常绿阔叶林凋落物分解和生态化学计量特征有助于了解森林生态系统凋落物分解过程对N沉降的响应机理。

Response of nutrient release and ecological stoichiometry of litter to simulated nitrogen deposition in evergreen broad-leaved forest in central Yunnan,China

We examined nutrient release and ecological stoichiometric characteristics of litters under N deposition in an evergreen broadleaved forest in Mopan Mountain in central Yunnan.Nylon net bag method was used for in situ decomposition of leaf litter and twig litter.There were four treatments,including control(CK,0 g N·m^-2·a^-1),low nitrogen(LN,5 g N·m^-2·a^-1),medium nitrogen(MN,15 g N·m^-2·a^-1),and high nitrogen(HN,30 g N·m^-2·a^-1).The results showed that after one year of N addition,the contents of C and N in leaf litter,twig litter and soil increased gradually with the increases of N addition rates,with increases of 0.3%-8.2%and 4.9%-69.0%,respectively.C/N gradually decreased with increasing N addition rates,with a decrease of 0.8%-37.8%.There was no significant difference in P content,C/P and N/P of twig litter under different treatments.Treatment duration and N application rate significantly affected the N and P contents and stoichiometric ratios of leaf litter,twig litter and soil.During the 1-year decomposition process,the residual rates of C,N and P in litters were successively in the modes of release,leaching-enriched-released and leaching-enriched.Exogenous N addition significantly inhibited the release process of C,N and P in litter.The contents of C and P in soil were significantly positively correlated with the contents of N and P in litter,while the contents of N in soil were significantly positively correlated with the contents of C and N in litter.There was a significant correlation of stoichiometric characteristics between litter and soils of evergreen broadleaved forest under N deposition.Our results were helpful to understand the response mechanism of litter decomposition process of forest ecosystem to N deposition.