滇中亚高山地带性植被凋落物分解对模拟氮沉降的响应

模拟氮（N）沉降对凋落物分解特征的影响对研究森林生态系统物质循环响应大气N沉降的内在机理和应对N沉降全球化具有重要意义。从2018年2月至2019年1月,对滇中亚高山常绿阔叶林（Evergreen broad-leaf forest）和高山栎林（Quercus semecarpifolia forest）两种地带性植被进行模拟N沉降试验,利用尼龙网袋法对两种林型凋落叶和凋落枝进行原位分解试验,N沉降处理水平分别为对照CK（Control check,0 g N m^-2 a^-1）、低氮LN（Low nitrogen,5 g N m^-2 a^-1）、中氮MN（Medium nitrogen,15 g N m^-2 a^-1）和高氮HN（High nitrogen,30 g N m^-2 a^-1）。结果表明：常绿阔叶林凋落叶和凋落枝分解率分别为44.84%和21.96%,均高于高山栎林的35.97%（凋落叶）和17.51%（凋落枝）;N沉降处理使得常绿阔叶林和高山栎林的凋落叶和凋落枝质量损失95%的时间在对照（CK）的基础上均有一定程度的增加,其中以HN处理下最为显著;经过1年的分解,两种林型凋落叶、枝纤维素和木质素降解均受到N沉降的抑制作用;两种林型中凋落物质量残留率、纤维素和木质素残留率三者间呈极显著正相关。针对滇中亚高山区域范围内的两种地带性植被,凋落物分解对N沉降的响应方向主要取决于凋落物基质质量,其中尤以纤维素和木质素为重要影响因素。

Response of litter decomposition of zonal vegetation to simulated nitrogen deposition in central Yunnan, China

The effects of simulated nitrogen (N) deposition on litter decomposition are of great significance for studying the inner mechanism of material cycle in forest ecosystem response to atmospheric N deposition and coping with the globalization of N deposition. From February 2018 to January 2019, a field experiment of simulated N deposition was conducted in two zonal vegetation (Evergreen broad-leaf forest and Quercus semecarpifolia forest) in central Yunnan province. The litterbag method was used for the litter (leaf and twig) in situ decomposition experiment in two forest types. Four treatment levels of N deposition were applied, i.e., control check(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 indicated that the decomposition rates of leaf and twig in Evergreen broad-leaf forest were 44.84% and 21.96%, respectively, which were higher than 35.97% (leaf) and 17.51% (twig) of Quercus semecarpifolia forest. Under N deposition, the time of 95% mass loss (T_95%) of leaf and twig in two forest types increased to a certain extent based on the control, and the most significant one was in HN treatment. After one year''s decomposition, the degradation of cellulose and lignin in leaf and twig litter were inhibited by N deposition. There was significantly positive correlation among litter mass remaining, cellulose and lignin remaining in two forest types. As for the two zonal vegetation in central Yunnan, the response direction of litter decomposition to N deposition mainly depended on the litter substrate, especially cellulose and lignin were important factors.