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设计了2种处理(即氮添加,100 kg N.hm-2.a-1;氮磷添加,100 kg N.hm-2.a-1+50 kg P.hm-2.a-1),研究了氮磷添加对亚热带北部常绿阔叶林土壤无机氮和氮素矿化的影响。结果表明,不同处理0～10 cm和10～20 cm土层无机氮(铵态氮+硝态氮)含量年平均值分别为:对照7.27和6.80 mg.kg-1、氮添加13.94和8.92 mg.kg-1、氮磷添加11.20和7.13 mg.kg-1,其中铵态氮分别占90.66%和91.15%、65.78%和72.85%、84.64%和85.08%。不同处理0～10 cm和10～20 cm土层的净氨化、净硝化和净氮矿化速率具有相似的季节性变化规律,即夏季氮素净转化速率最高,冬季氮素净转化速率最低,春季和秋季氮素净转化速率有一定差异,但不显著。研究表明,养分添加使土壤年平均净氮矿化速率下降,氮添加使土壤硝化速率下降,氨化速率上升;而氮磷添加使硝化速率上升,氨化速率下降。养分添加对森林生态系统的氮动态影响效应尚需长期定位观测。
Two treatments were designed (N addition, 100 kg N · hm -2 · a -1; addition of N and P, 100 kg N · hm -2 · a -1 +50 kg P · hm -2 · a -1) The effects of nitrogen and phosphorus addition on soil inorganic nitrogen and nitrogen mineralization in evergreen broadleaved forest in the northern subtropics were studied. The results showed that the annual average contents of inorganic nitrogen (ammonium nitrogen + nitrate nitrogen) in 0 ~ 10 cm and 10 ~ 20 cm soil layers were 7.27 and 6.80 mg · kg-1, and 13.94 and 8.92 mg nitrogen .kg-1, nitrogen and phosphorus added 11.20 and 7.13 mg.kg-1, respectively, of which ammonium accounted for 90.66% and 91.15%, 65.78% and 72.85%, 84.64% and 85.08%, respectively. The net ammonification, net nitrification and net nitrogen mineralization rates of 0 ~ 10 cm and 10 ~ 20 cm soil layers in different treatments had similar seasonal changes, that is, the net nitrogen transformation rate was the highest in summer and lowest in winter There was a certain difference between the net nitrogen conversion rate in spring and autumn, but not significant. The results showed that nutrient addition decreased the average net nitrogen mineralization rate of soil, while nitrogen addition decreased soil nitrification rate and ammonification rate, while nitrogen and phosphorus increased nitrification rate and ammonification rate. The effect of nutrient addition on nitrogen dynamics of forest ecosystem still needs long-term positioning observation.