N沉降下土壤动物群落的响应:1年研究结果总述2681258920

2003年7月至2004年8月,选择了苗圃、针叶林、混交林和季风林4个生态系统,采用模拟的方法,人为构建N沉降增加梯度系列,即对照、低N处理（50 kg/(hm2·a)）、中N处理（100 kg/(hm2·a)）、高N处理（150 kg/(hm2·a)）和倍高N处理（300 kg/(hm2·a)）,在14个月的时间内,对土壤动物群落在N沉降下的响应进行了持续观测研究.研究结果表明,土壤动物群落无论在时间尺度和空间尺度（垂直分布）都发生了明显的变化.生态系统类型的影响很显著,季风林和针叶林增长模式的不同,最终导致3个森林土壤动物分布格局的根本改变.苗圃样地N处理具有明显的阈值效应.虽然整体上森林样地N处理梯度未产生显著影响,但它在与不同植被、不同取样期的交互作用中可以清楚表现出来.N沉降存在明显的累积效应.在持续大量N沉降的作用下,动物向土壤深层趋避,显示N处理的负效应.N沉降的阈值效应和累积效应也都符合中度干扰理论.最后,该文还对N沉降对土壤动物群落的影响机制进行了初步探讨,认为N沉降可能通过对土壤无机环境的改变间接影响较高营养阶——土壤动物群落,而N沉降处理的阈值效应、生态系统成熟度及处理时间累积对试验效果的影响,本质上可能均反映了生态系统N饱和状态对N沉降的响应. 

Effects of N deposition on soil fauna: a summary for one year

Impacts of simulated atmospheric nitrogen (N) deposition on soil fauna were studied during 14 months from July 2003 to August 2004. Dissolved NH4NO3 at the following rates: control(0), low (50 kg/(hm2·a)), medium (100 kg/(hm2·a)), high (150 kg/(hm2·a))and double high (300 kg/(hm2·a)), and it was sprayed during the period. Plots were built in seedling stands (SD), pine forests(PF), mixed pine and broadleaved forests (MF) and monsoon evergreen broadleaved forests (MEBF) in subtropical China. It suggested that soil fauna’ responses were correlated significantly with the type of ecosystem. N levels influenced soil fauna significantly in SD, which indicated the existence of a threshold about the effects of N deposition. The data, averaged over the entire period and all forests, did not show any significant effects of N levels on soil fauna. But it could be discovered in the interactions between N and forest type and interactions between N and sampling date. Accumulated effects from N deposition were found. Under continuous and high N deposition, soil fauna became concentrated into the deeper soil, which also indicated the negative effects of N. The threshold and accumulation effects of N deposition could also be predicted by an intermediate disturbance hypothesis (IDH). Finally a preliminary discussion was presented on the mechanisms of the effects of N deposition on soil fauna. The responses of soil fauna to N deposition might indirectly be shown in inorganic soil changes in the environment, and the effects of N levels, ecosystem types and time accumulation might reflect the reaction of “N saturation" status of the ecosystem to atmospheric N deposition.522011