氮磷添加对苦槠次生林凋落物量及其养分动态的影响

Effect of Nitrogen and Phosphorus Addition on Litterfall Production and Nutrient Dynamics in a Castanopsis sclerophylla Secondary Forest

中国是全球高氮沉降区之一,氮沉降对生态系统的结构和功能产生严重影响。为了探讨氮沉降增加对森林生态系统的影响,选择苦槠次生林开展氮磷添加试验,以揭示其凋落物生产及其养分归还对氮磷添加的响应。笔者采用野外模拟试验,设计4种处理,分别为对照(CK)、磷(P)、高氮(HN)和高氮加磷(HN+P),每个处理重复3次。结果表明:通过1年的试验观测,经P、HN、HN+P处理后,年凋落物量分别为8.69、8.11、9.41 t/hm2,明显高于对照林分(7.68 t/hm^2);P、HN、HN+P处理均增加养分归还总量,大小顺序为:HN+P>P>HN>CK,氮磷添加同样增加了N、P、K、Ca、Mg的年归还量,大小顺序为:N>Ca>K>Mg>P。研究表明,氮磷添加均提高林分凋落物量和养分归还量,高氮加磷有助于维持土壤氮磷动态平衡,显著提高凋落物产量。

China is one of the regions with high N deposition in the world. Nitrogen deposition has a serious impact on the structure and function of forest ecosystem. The paper aims to reveal the effects of increasing N deposition on litter production and related nutrient returns in forest ecosystem, an experiment of N and P addition was conducted in a secondary Castanopsis sclerophylla forest. In the field simulated experiment, 4 treatments were designed as CK, P addition（P）, high N addition（HN）, and high N＋P addition（HN＋P）, with 3 replicates for each treatment. The results from the one- year observation showed that： annual litterfall productions were 8.69, 8.11, and 9.41 t/hm2 for P, HN and HN＋P treatment, significantly higher than that of the CK（7.68 t/hm^2）. The amount of nutrient returns by litterfall was all increased to some degree due to N and P addition. The order of the total nutrient returns was： HN ＋ PPHNCK. The N and P addition also increased the amount of nutrient returns annually. The N and P addition increased the nutrient elements return in an order of NCaKMgP. These results indicated that N and P addition improved the litterfall quantity and related nutrient return. High N plus P could maintain the balance of soil nitrogen and phosphorus,significantly increase litter productivity.