模拟氮沉降对温带不同森林类型土壤氮矿化速率的影响

Influence of Simulated Nitrogen Deposition on Soil Nitrogen Mineralization Rate Under Different Forest Stands

通过室内模拟不同氮形态(NH4+-N、NO3--N、NH4+-N+NO3--N)沉降实验,研究不同氮形态沉降对温带不同森林类型(椴树红松混交林、白桦天然次生林、红松人工林和落叶松人工林)土壤氮矿化速率的影响。结果表明:在整个培养期间,与对照相比,经过氮沉降土壤净氨化速率、净硝化速率及净矿化速率都呈现出增长趋势,而其增加的程度又取决于森林类型、土层、氮处理类型和处理时间。不同林型土壤净氨化速率、净硝化速率及净矿化速率受氮沉降影响不同,混交林对氮沉降的响应要弱于阔叶林,高于针叶人工纯林;土壤A层比土壤B层对氮沉降敏感;以铵态氮形态沉降时对铵态氮含量、净氨化速率影响较大,以硝态氮形态沉降时对硝态氮含量、净硝化速率影响较大,混合形态的氮沉降要比单种形态的氮沉降使土壤净氨化速率、净硝化速率及净矿化速率增加幅度更高;氮沉降时间越长,土壤净氨化速率、净硝化速率及净矿化速率与对照差距越大,说明氮沉降对土壤的影响存在累加效应。

An indoor experiment was conducted to study the effects of different forms of simulated nitrogen deposition（NH＋4-N,NO-3-N,NH＋4-N＋NO-3-N） on soil nitrogen mineralization rate under different temperate forest stands（Korean pine plantation,larch plantation,natural Korean pine and linden mixed forest,natural secondary birch forest）.The results showed that during the whole incubation period,nitrogen deposition increased soil net ammoniation rate,net nitration rate and net mineralization rate,as comparison with the control,but the increments differed with forest stands,soil layers,nitrogen treatment types and treatment duration.The influence of nitrogen deposition on soil net ammoniation rate,net nitration rate and net mineralization rate under different forest stands were different.The soil under mixed forests had weaker response to nitrogen deposition than under broad-leaved forests,but stronger response than under artificially pure coniferous forest,soil layer A was more sensitive to nitrogen deposition than soil layer B.Ammoniation nitrogen deposition had larger effect on soil NH＋4-N and net ammoniation rate,nitrate nitrogen deposition had larger effect on soil NO-3-N and net nitration rate,while mixed ammoniation and nitrate nitrogen deposition increased soil net ammoniation rate,net nitration rate and net mineralization rate with higher extent than single form of nitrogen deposition.The longer nitrogen deposition under different forest stands increased the difference in the rates as compared with the control,suggesting the additive effect of the mixed ammoniation and nitrate nitrogen deposition on forest soil.