Human activities have greatly changed the pathway and rate of nitrogen transferred from atmosphere to terrestrial ecosystems worldwide. Anthropogenic nitrogen enrichment, as a result of chronic nitrogen deposition, has caused a wide range of impacts on ecosystem structures and functions. In this paper, we summarize the main effects of anthropogenic nitrogen addition on terrestrial ecosystems as follows:
1) Increased nitrogen input may have influences on plant production and ecosystem carbon storage, and the direction and magnitude of responses are determined by initial nitrogen status of ecosystems (N-limited or N-saturated) and local properties of vegetation and soil;
2) Chronic nitrogen addition can also alter soil nitrogen cycling, decrease the capability of soil to retain N, even lead to soil acidification, depletion of base cation, and affect decomposition of SOC;
3) Both high rate of nitrogen deposition and chronic low nitrogen addition may accelerate losses of N-contained gas, but the magnitude of influences depends on initial status of ecosystem (N-limited or P-limited);
4) N enrichment will affect species richness in terrestrial ecosystems, plant communities' structures and dynamics. It may also contribute to forest expansion into grasslands, alter species composition and diversity of mycorrhizal fungi;
5) Continuous N input and the resulting changes in plant composition and physiological feature may have effects on consumption rate and population dynamics of herbivorous insects, and eventually change ecosystem trophic structure through food chain;
6) Since the influences of N addition, increased concentration of CO2 and O3 on ecosystem properties and processes are interdependent, it is difficult to distinguish each effect.
We also summarized the current status of researches on N deposition in China, and proposed the potential research activities and recommendations.