Abstract: Based on literature data, the effect of increased deposition of atmospheric nitrogen on forest ecosystem is discussed in this paper. During last decades,the deposition of atmospheric nitrogen is increased dramatically, and the relationship between nitrogen deposition and nitrogen emission is linear. In some areas, nitrogen deposition has exceeded the N requirement by forest ecosystem. The stimulation of plant growth and the damage to mycorrhizae by the increased nitrogen deposition, the exchange of absorbed excess NH₄⁺ forother nutrient canons in plant,and the competitive inhibition of the uptake of other nutrient cations by high level of NH₄⁺ in soil can lead to the deficiency of other nutrients in plant and the disorder of forest nutrition. The increase in nitrogen deposition will result in enhanced nitrification, promoted leaching of NO₃^- and concomitant base canons, accelerated soil acidifieation, and forced Al and Mn mobilization. A high level of nitrogen inplant due to the assimilation of large amount of excess nitrogen will increase the susceptibility of tree plant to the stress of cold, frost, fungal pathogens and possible insect attacks. The chronic increase in nitrogen deposition can induce the change in community through interfering with successional dynamics.

Key words: Soil acidification, Susceptibility to stress, Community change, Atmospheric nitrogen deposition, Forest ecosystem, Nutritional disorder, utilization, potassium level, nitrogen, Malus hupehensis, absorption, apple