常绿阔叶林凋落叶、枝分解过程对模拟N沉降的响应

Responses of leaf and twig litter decomposition to simulated N deposition in the evergreen broad-leaved forest

【目的】为深入了解N沉降对滇中高原地带性植被凋落物分解过程的影响,为区域森林可持续经营提供理论支持。【方法】在新平县磨盘山常绿阔叶林模拟N沉降和凋落物原位分解试验,测定CK(0 g·m^(-2)·a^(-1))、LN(10 g·m^(-2)·a^(-1))、MN(20 g·m^(-2)·a^(-1))和HN(25 g·m^(-2)·a^(-1))下常绿阔叶林凋落叶、枝分解过程的基质质量指标。【结果】1)经过1 a的分解,凋落叶和枝质量残留率分别为52.0%~57.4%和74.2%~77.9%,分解系数分别为0.475~0.595和0.119~0.152 kg·kg^(-1)·a^(-1),木质素和纤维素残留率变化幅度分别为54.5%~66.2%、66.8%~77.8%和37.9%~48.5%、64.2%~74.2%;2)分解1 a后,N沉降处理使凋落叶、枝木质素残留率和纤维素残留率均显著增加,其中,木质素残留率增加3.2%~11.7%(凋落叶)、1.9%~11.0%(凋落枝),纤维素残留率增加2.9%~10.6%(凋落叶)、2.2%~10.0%(凋落枝),木质素和纤维素降解被抑制,HN处理下更显著,即N沉降显著抑制了凋落叶和枝的分解;3)经1 a的分解后,N沉降处理使C/N、木质素/N、纤维素/N含量均显著降低,其中,凋落叶C/N、木质素/N、纤维素/N变化范围分别为12.4%~15.1%、5.1%~15.7%、1.6%~5.0%;凋落枝分别为4.2%~15.2%、5.0%~13.4%、3.5%~10.1%。【结论】N沉降通过影响凋落物基质质量(降低C/N、木质素/N、纤维素/N),从而减缓常绿阔叶林凋落叶、枝的分解速率,其中C/N、木质素/N、纤维素/N更能反映其分解过程。

【Objective】The objective of this article was to explore the effect of N deposition on the decomposition process of zonal vegetation litter in the Central Yunnan Plateau,to provide theoretical support for the regional sustainable management of forests.【Methods】The N deposition and litter in-situ decomposition experiment was simulated in the evergreen broad-leaved forest of Mopan Mountain in Xinping County.The matrix quality indexes of the leaf and twig litter decomposition in the evergreen broad-leaved forest under CK(0 g·m^(-2)·a^(-1)),LN(10 g·m^(-2)·a^(-1)),MN(20 g·m^(-2)·a^(-1))and HN(25 g·m^(-2)·a^(-1))conditions were determined.【Result】1)After 1 year of decomposition,the mass residual rates of leaf and twig litters were 52.0%-57.4%and 74.2%-77.9%,respectively,and the decomposition coefficients were 0.475-0.595 and 0.119-0.152 kg·kg^(-1)·a^(-1).The changes in the residual rates of lignin and cellulose were 54.5%-66.2%,66.8%-77.8%and 37.9%-48.5%,64.2%-74.2%,respectively.2)After 1 year of decomposition,N deposition treatment significantly increased the residual rates of lignin and cellulose in leaf and twig litters,and the lignin residual rate increased by 3.2%-11.7%(leaf litter)and 1.9%-11.0%(twig litter),and the cellulose residual rate increased by 2.9%-10.6%(leaf litter)and 2.2%-10.0%(twig litter).The degradation of lignin and cellulose was inhibited,especially under HN treatment.In other words,N deposition significantly inhibited the decomposition of leaf and twig litters.3)After 1 year of decomposition,N deposition treatment significantly reduced the contents of C/N,lignin/N and cellulose/N.The variation ranges of C/N,lignin/N and cellulose/N in leaf litters were 12.4%-15.1%,5.1%to 15.7%and 1.6%to 5.0%,which were 4.2%to 15.2%,5.0%to 13.4%,and 3.5%to 10.1%in twig litters.【Conclusion】N deposition can slow down the decomposition of leaf and twig litters in the evergreen broad-leaved forest by affecting the quality of litter matrix(reducing C/N,lignin/N,cellulose/N),among which C/N,lignin/N and cellulose/N can better reflect the decomposition process.