模拟氮沉降对甜槠林分凋落物及主要养分归还量的影响

Effects of Simulated Nitrogen Precipitation on Litterfall and Related Nutrient Returns in a Castanopsis eyrei Forest

选取亚热带典型的常绿阔叶甜槠林为研究对象,从2011年4月至2013年6月进行模拟氮(N)沉降试验,以探讨甜槠林凋落物养分归还量对N沉降的响应。氮沉降水平分别为:对照(CK,0 kg N hm-2a-1),低氮(LN,50 kg N hm-2a-1),高氮(HN,100 kg N hm-2a-1),高氮+磷(HN+P,100 kg N hm-2a-1+50 kg P hm-2a-1),每个处理重复3次。在模拟氮沉降2 a后,于2012年7月开始收集各样地的凋落物样品,分析凋落物及其养分归还量。结果表明:不同处理凋落物量没有显著差异,表明氮沉降增加没有显著提高林分凋落物产量;不同处理落叶、落枝中N、P、K、Ca、Mg含量均无显著差异,表明氮沉降亦没有显著增加凋落物各养分含量;模拟氮沉降处理均增加了各养分元素年归还量,但不同元素对N沉降的响应不同。N、K和Mg年归还量与CK存在显著差异,而P和Ca年归还量与CK处理无显著差异。

A simulated nitrogen pre cipitation experiment was conducted in a subtropical evergreen broad-leaved Castanopsis eyrei forest started from April 2011 in southern Anhui. Four treatments were designed such as CK(0 kg N hm-2a-1), low N(LN, 50 kg N hm-2a-1), high N(HN, 100 kg N hm-2a-1), high N+P(HN+P, 100 kg N hm-2a-1+ 50 kg P hm-2a-1), with three replicates for each treatment. After two-year simulated nitrogen precipitation,litterfall was measured from July 2012. The results showed that different nitrogen additions did not significantly increase litter production. The concentrations of N, P, K, Ca and Mg in litter fractions(leaf and twig litter) were also not significantly increased among different treatments. The different nutrient elements showed variant responses to simulated nitrogen precipitation. In comparison with the control, N additions significantly increased annual nutrient returns of N, K and Mg. However, there were no significant differences on the annual returns of P and Ca between treatments and controls.