兴安落叶松林土壤的无机态氮及氮矿化速率

摘要

采用野外封顶埋管法对兴安落叶松4种典型林型：草类-兴安落叶松林、赤杨-兴安落叶松林、杜香-兴安落叶松林、柴桦-兴安落叶松林土壤无机态氮及氮矿化速率变化特征进行了对比研究。结果表明：NH4-N是土壤有效氮的主要存在形式，NH4-N在无机氮中所占比例约为31％～82％，NO3-N在无机氮中所占比例约为18％～69％。4种林型土壤的氨化作用强于硝化作用，二者均是7月份活动最强烈，整个生长季中，氨化速率的变化范围是0．28～1．59μg· g-1· d-1，硝化速率的变化范围是-0．28～1．18μg· g-1· d-1。林型间差异不显著，氨化速率月份和林型之间没有显著的交互作用，硝化速率月份和林型之间有显著的交互作用（P＜0．0001）。4种林型土壤的氮矿化速率存在季节性变化，土壤平均矿化速率从大到小依次为：赤杨林（1．04±0．15）μg· g-1· d-1、杜香林（1．03±0．31）μg· g-1· d-1、柴桦林（1．03±0．40）μg· g-1· d-1、草类林（1．02±0．22）μg· g-1· d-1。不同林型之间土壤氮矿化速率差异不显著，林型和月份之间有显著的交互作用（P＜0．02）。%The experiment was conducted to investigate the variations of inorganic nitrogen content and N mineralization in soil under four different tropical forests by the Close-Top Tube Incubation method in Daxing’an Mountain including Grass-Larix gmelini forest, Alnus-Larix gmelini forest, Ledum Sphagnum-Larix gmelini forest, Betula fruticosa-Larix gmelini forest. Ammonia nitrogen is the major form of inorganic nitrogen , the proportion of NH4-N to the total inorganicis 31%-82%, and that of NO3-N to the total inorganic is 18%-69%.Soil ammonification rates and nitrificationrates are the highest in July,and nitrification is the dominant process in the forests.Soil ammonification rates varies from 0.28 to 1.59 mg· kg-1 · d-1 and that of nitrification rates varies from-0.28 to 1.18 mg·kg -1 · d-1 , and the difference is not significant.Nitrogen mineralization rates show significant seasonalvariations .Annual nitrogen mineralizationrates in four forests are in the order of Alnus-Larix gmelini forest, (1.04±0.15)mg· kg-1· d-1>Ledum Sphagnum-Larix gmelini forest, (1.03±0.31)mg· kg-1· d-1>Betula fruitcosa-Larix gmelini forest, (1.03±0.40)mg· kg-1·d -1>Grass-Larix gmelini forest, (1.02±0.22) mg· kg-1 · d-1 .Soil nitrogen mineralization rate is not significant in different forest types, but the interaction in forest type and month is significant (P<0.02).