中文摘要：

对12年生杉木人工林开展N0（0kgN·hm-2a-1）、N1（60kgN·hm-2a-1）、N2（120kgN·hm-2a-1）和N3（240kgN·hm-2a-1）4种水平的模拟氮沉降试验,探讨亚热带森林土壤酶（过氧化氢酶、蔗糖酶和脲酶）活性对氮沉降增加的响应。试验采取2种施氮方式,即在缓冲区采取1年1次性施入氮,而在中心区每月施入等量氮。结果表明：缓冲区1次性施氮后30天内每10天土壤酶活性变化趋势和中心区按月施氮后酶活性动态均表现为N1始终促进3种酶活性（相对于N0处理）;N1和N2处理对土壤酶活性的影响依施氮时间和土层深度不同而异,没有表现出明显的促进增加或抑制作用;随土层深度增加,3种酶活性均表现出明显降低趋势。

英文摘要：

To investigate soil enzyme activities （catalase, invertase and urease） in response to increased nitrogen deposition in the subtropical plantation of Chinese Fir （ Cunninghamia lanceolata） , a field experiment with 20 m x 20 m plots was conducted in a 12-year-old Chinese Fir plantation for 2 years. Nitrogen loadings were designed at 4 levels of 0, 60, 120, 240 kg N-hm-2a-1, referred to NO, N1, N2 and N3, respectively, with 3 replicates in each treatment. In the inner 15 m ~ 15 m of the plot, solution of CO （NH2）2 was sprayed on the forest floor each month, and on the margin of the plot between the inner plot and the boundary, nitrogen was fertilized once a year. The results showed that compared to NO treatment, N1 consistently had a positive effect on activities of soil catalase, invertase and urease, determined both by variations of soil enzyme activities in the center plot area every 10 days after nitrogen treatment and monthly dynamics （July through September） in the buffered zone. However, the effects of N2 and N3 treatments were found to vary with time and soil depth. The activities of these three enzymes decreased significantly with increasing soil depth.