原始云冷杉、红松林树木生长对氮沉降的响应

Response of tree growth to nitrogen deposition in spruce-fir-Korean pine virgin forest in Lesser Khingan Mountains in northeastern China

本文通过野外控制试验,设置4个梯度的施氮处理,分别为对照(CK,不加氮)、低氮(T_L,5 g/(m^2·a))、中氮(T_M,10 g/(m^2·a))、高氮(T_H,15 g/(m^2·a)),研究云冷杉红松林主要树种的径生长对氮沉降增加的响应。结果表明,枫桦径生长随氮添加梯度的增加出现了先促进后抑制的趋势;臭冷杉和红松径生长随氮添加梯度的增加而受到抑制,其中臭冷杉表现出明显的衰退现象甚至死亡;花楷槭则表现出较为复杂的响应,可能与该树种对不同梯度氮添加的响应机制不同有关。同时还发现,各处理、各树种的胸径大小与径生长量存在相关性,可能与树种年龄及其所处的生态位相关。研究表明,氮沉降改变树木生长速率和死亡率,可能影响地上生态系统碳库和整个生态系统碳循环。

In this article,through field control experiment,four gradient nitrogen treatments were set as control（CK,no nitrogen（N）,low-N（T_L,5 g/（m^2·year））,medium-N（T_M,10 g/（m^2·year））and high-N（T_H,15 g/（m^2·year））,in order to study the responses of DBH growth of main species to the increasing nitrogen deposition in spruce-fir-Korean pine virgin forest.The results showed that,with the increase of nitrogen adding gradient,the DBH growth of Betula costata appeared a trend of promoting first and then suppression.The DBH growth of Abies nephrolepis and Korean pine would be suppressed due to the increase of nitrogen adding gradient,and long-term nitrogen adding can lead to the degradation or death of A.nephrolepis.While Acer ukurunduense appeared more complex response,which was possibly related to the different response mechanism of this species to the varied nitrogen adding gradients.Meanwhile,it was also found that there existed a certain relationship between the amount of DBH and DBH growth,which was possibly related to tree age and its situated niche.Our study showed that nitrogen deposition could change the growth rate and mortality of trees,and then influence the aboveground ecosystem carbon pool and the carbon cycle of whole ecosystem.