森林土壤氮素转换及其对氮沉降的响应

Nitrogen transformations in forest soils and its responses to atmospheric nitrogen deposition: a review

近几十年人类活动向大气中排放的含氮化合物激增 ,并引起大气氮沉降也成比例增加。目前 ,氮沉降的增加使一些森林生态系统结构和功能发生改变 ,甚至衰退。近 2 0 a欧洲和北美有关氮沉降及其对森林生态系统的影响方面的研究较多 ,而我国少有涉及。森林土壤氮素转换是森林生态系统氮素循环的一个重要的组成部分 ,而矿化、硝化和反硝化作用是其核心过程 ,氮沉降作为驱动因子势必改变森林土壤氮素转换速度、方向和通量。根据国外近 2 0 a有关研究 ,首先介绍了森林土壤氮素转换过程和强度 ,论述森林土壤氮素在生态系统氮素循环中的作用 ,然后在此基础上 ,介绍了氮沉降对森林土壤氮素循环的研究途径 ,探讨了氮沉降对森林土壤氮素矿化。

Atmospheric nitrogen deposition remains elevated in industrial regions of the world and is accelerating in many developing regions. Chronically elevated atmospheric N inputs to forest can lead to changes in tree growth, mortality, and species composition, and to possible declines in soil fertility and drainage water quality. A large number of experiments have been carried out in Europe and Northern America to identify the specific role of atmospheric N in changes observed in water quality and tree health. Recently, the emissions of nitrogenous compounds from industry and agriculture have also been increasing rapidly in China. However, little information about the impacts of nitrogen deposition is available for forest ecosystems in China. Elevated atmospheric nitrogen input, as a driving environmental factor, has altered the nitrogen cycle of forest ecosystems, especially soil nitrogen transformations. In this paper, based on available scientific evidence we reviewed the controlling factors for nitrogen transformations in forest soils and its responses to atmospheric nitrogen deposition. The review mainly includes the following four aspects: (1) the biological processes and magnitudes of nitrogen transformations in forest soils; (2) the roles of nitrogen transformations in nitrogen cycling of forest ecosystems; (3) the current methods for study forest nitrogen transformations; (4) the potential effects and its mechanisms of nitrogen deposition on forest soil nitrogen mineralization, nitrification and denitrification.