森林生态系统对大气氮沉降的响应

氮是陆地生态系统中三大营养元素之一,在森林生态系统中被视作主要的限制生长因子。近年来,因工农业的迅猛发展而产生越来越多的含氮化合物,大大增加了氮向全球大气的排放。据研究发现,如果氮的输入已达饱和甚至超过生态系统所能承受的临界负荷,就会带来负面效应。本文主要从以下几方面综述了国内外学者关于大气氮沉降对森林生态系统的影响:1.与大气氮沉降相关的内容,包括1)氮饱和和2)确定氮沉降临界的指示树种;2.国内外的研究进展;3.大气氮对森林生态系统的影响,包括1)导致营养失调,2)对胁迫敏感性的增强,3)加速森林土壤酸化,4)氮淋溶的增加,5)物种多样性的减少和6)氮沉降的评价方法。

Impact of Forest Ecosystems on Atmospheric Nitrogen Deposition

Nitrogen is one of the three essential nutrients in the terrestrial ecosystem and is regarded as a main limited factor in the forest ecosystem.With the rapid development of agriculture and industry in recent years,more and more nitrogenous compounds have been emitted into the atmosphere.As a result,the terrestrial ecosystem has been damaged seriously,espically forest ecosystem.It is reported that if nitrogen has got to saturation or even exceeded the critical load value of ecosystem,it will be negative to the ecosystem.This paper treats of some concepts of atmospheric nitrogen deposition at first,such as nitrogen saturation the indicator of nitrogen deposition value,and then summarizes the studies of nitrogen deposition at home and aboard.At last,much attention is paid to the effect of atmospheric nitrogen on the forest ecosystem.It is found that nitrogen deposition can break the nutrient balance,strenghten the sensitivities to stress and accelerate the soil acidification process,and can also lead to the increase of nitrogen leaching from soil and the decrease of biodiversity.In order to assessing the effect of nitrogen deposition correctly,some methods are introduced which have been used by John D.Aber.