中文摘要：

通过野外模拟试验，选择中亚热带针叶林（杉木林）和阔叶林（浙江桂林和罗浮栲林）森林生态系统，设3个施氮水平CK（对照）、低氮[30kg／（hm2·a）]和高氮[100kg／（hm2·a）]及2个凋落物处理，研究施氮对土壤主要形态氮质量分数的影响、动态变化及凋落物在其中的作用．结果表明：与CK相比，高氮处理可瞬时（3d）提高森林土壤氮质量分数，但施氮后持续效应的影响降低．与保留凋落物相比，去除凋落物在施氮的持续效应中，可降低阔叶林土壤”（铵态氮）18．2％，而杉木林土壤的氮质量分数则略有升高．去除凋落物下施氮的持续和瞬时效应可增加各种林下土壤的”（硝态氮），其中浙江桂林土壤w（硝态氮）分别增加58．9％和38．2％，罗浮栲林土壤分别增加7．O％和30．O％，杉木林土壤分别增加-17．1％和9．0％．可见凋落物在施氮连续事件中存在复杂的短期和长期相互影响．阔叶林土壤”（SON）（SON为可溶性有机氮）较高，并且其微生物”（SON）及其占微生物”（TN）的比例高于杉木林土壤，而杉木林土壤微生物”（铵态氮）及其占微生物w（TN）的比例高于阔叶林土壤．

英文摘要：

A field-simulated experiment on nitrogen deposition was conducted to investigate the effects of added nitrogen on ammonium and nitrate nitrogen, their dynamics and the role of litter in nitrogen transformation under nitrogen addition condition. The experiment was carried out in the forest system of subtropical coniferous （Cunninghamia lanceolata） and broad-leaved tree （Cinnamomum chekiangense and Castanopsisfabric） with three nitrogen levels （ control （ CK, 0 kg/（ hm2 ~ a） ） , low nitrogen （ LN, 30 kg /（ hm2 ~ a） ） and high nitrogen （HN, 100 kg/（hm2-a） ）） and two litter treatments （retention of litter layer/isolation litter （natural status, referred to as the ＂retain litter＂, Y） and the removal of litter layer / isolation litter （ referred to as ＂the removal of litter＂, N） ） established. The results showed that, compared with the control, under simulated nitrogen deposition condition, the ttN treatment significantly enhanced ammonium nitrogen content in broad-leaved forest soil, raised the amount of soil nitrate for C. fabri and C. lanceolata after three days of nitrogen addition immediately. However, the effects were not significant after three months of nitrogen addition. The dynamics of ammonium nitrogen was different before and after the simulation of nitrogen deposition and it was different from nitrate and soluble organic nitrogen （SON） after nitrogen deposition. The ammonium nitrogen contents in microorganism not increased with nitrogen deposition increasing for the broad leaved forest soil. However, compared with before fertilization, nitrogen deposition significantly increased after nitrogen deposition in summer. Compared with intact litter treatment, ammonium nitrogen in soil decreased by 17.5% and 18.9% for broad-leaved forest with litter removal before fertilization application and a small change was found for Chinese fir forest. Compared with litter intact treatment, the nitrate increased by 58.9% and 38.2% for C. chekiangense_ by 7.0% and 3