中文摘要：

由于人类活动加剧，世界许多地区的大气氮沉降出现明显的增加，对森林植物和土壤产生明显影响．在福建沙县，通过野外模拟试验研究了杉木人工林针叶养分含量对氮沉降增加的响应．试验设计为4种处理．分别为NO（N．0kghm^-2·a^-1，对月强）、N1（N，60kg·hm^-2·a^-1）、N2（N，120kg·hm^-2·a^-1）和N3（N，240kg·hm^-2·a^-1），每处理重复3次．通过3a监测发现，相对于NO处理，N1、N2和N3处理分别使杉木针叶平均N含量增加18．25％、11．68％和13．14％，而C／N比值分别下降15．07％、9．96％和12．01％．尽管养分含量随时间变化表现出一定的波动，但氮沉降增加在一定程度上降低了针叶中的P、K、Ca、Mg含量，致使N／P、N／K、N／Ca、N／Mg比值上升，影响了针叶的养分平衡．

英文摘要：

The deposition of reactive N has increased remarkably in many regions due to human activities. The increased N supply has a fertilization effect on forest ecosystems, but also negatively impacts plant nutrition, soil chemistry and productivity. A field simulated experiment, with annual nitrogen additions at four levels of N0 （0 kg N hm-2 a-1, as CK）, N1 （60 kg N hm-2 a-1）, N2 （120 kg N hm-2 a-1） and N3 （240 kg N hm-2 a-1）, was conducted in a Chinese fir （Cunningkamia lanceolata） plantation in central western Fujian to study the effect of nitrogen deposition on foliar nutrient contents. Each treatment comprised three replicate plots of 20 m × 20 m which were sprayed with urea on the forest floor at the beginning of each month, lasting from January 2004 to December 2006. Based on three years＇ foliar analyses, N treatments （N1, N2 and N3） increased N concentrations in the leaves of C. lanceolata by 18.25%, 11.68% and 13.14%, but decreased C/N ratios by 15.07%, 9.96% and 12.01%, respectively, compared with NO. Nitrogen loads generally reduced the contents of P, K, Ca and Mg in the leaves. Although the nutrient contents fluctuated with the time, N loads significantly increased the N/P, N/K, N/Ca and N/Mg ratios, leading to imbalance of nutrients in the leaves.