模拟氮沉降增加对南亚热带主要森林土壤动物的早期影响

Early responses of soil fauna in three typical forests of south subtropical China to simulated N deposition addition.

对模拟氮沉降增加条件下3种南亚热地带代表性森林(季风常绿阔叶林、针阔混交林和马尾松纯林)内土壤动物群落的早期响应特征进行了比较研究.试验采用模拟的方法,人为构建了一个氮沉降增加梯度系列,即对照、低氮处理(50kg·hm-2·yr-1)、中氮处理(100kg·hm-2·yr-1)和高氮处理(150kg·hm-2·yr-1).结果表明,不同林分对氮沉降增加的响应不同;季风林与针叶林表现了两种截然相反的变化趋势,前者反映的是负向效应,土壤动物的3项指标均明显下降,而后者则反映出明显的正向效应,使得针叶林土壤动物的各项指标达到混交林,甚至季风林的水平;氮沉降增加对混交林则没有表现出明显的作用.不同氮沉降增加水平所产生的效应也不完全相同.在季风林内,参比对照,中氮处理往往表现出显著的负向效应(P<0.05),而低氮处理反应不明显;在针叶林内,氮处理的正向效应随着处理的加强而持续上升,尤其是对于土壤动物类群数指标,这种持续性均达到了显著性水平(P<0.05).可以认为,这些结果反映了森林生态系统对氮饱和的响应机制.

In this paper,simulated N deposition addition (0,50,100 and 150 kg·hm^(-2)·yr^(-1)) by spreading water or NH_4NO_3 was conducted to study the early responses of soil fauna in three typical native forests (monsoon evergreen broadleaf forest,pine forest,and broadleaf-pine mixed forest) of subtropical China.The results showed that in monsoon evergreen broadleaf forest,N deposition addition had an obviously negative effect on the three indexes for soil fauna,but in pine forest,the positive effect was significant (P<0.05),and the soil fauna community could reach the level in mixed forest,even that in monsoon evergreen broadleaf forest at sometime.The responses in mixed forest were not obvious.In monsoon evergreen broadleaf forest,the negative effects were significant (P<0.05) under medium N deposition,but not under low N deposition.In pine forest,the positive effect was significant (P<0.05) under high N deposition,especially for the number of soil fauna groups.The results obtained might imply the N saturation-response mechanisms of forest ecosystems in subtropical China,and the conclusions from this study were also consisted with some related researches.