西双版纳不同热带森林土壤氮矿化和硝化作用研究

NITRIFICATION AND NET N MINERALIZATION RATE OF SOILS UNDER DIFFERENT TROPICAL FORESTS IN XISHUANGBANNA,SOUTHWEST CHINA

1998年7月，用埋袋法对西双版纳热带季节雨林、崖豆藤（Mellettialeptobotrya）次生林、季节雨林内林窗和轮歇地土壤的氮矿化和硝化作用进行了研究。研究结果表明季节雨林和崖豆藤次生林的格局基本相同，氮净矿化速率分别为6．55mgN·kg－1·30d-1和6．37mgN·kg-1·30d-1，硝化速率分别为16．28mgN·kg－1·30d-1和16．38mgN·kg-1·30d-1。而林窗下和轮歇地土壤的氮净矿化速率和硝化速率均为负值，氮净矿化速率分别为-7.85mgN·ks-1·30d-1和-10．69mgN·kg-1·30d-1，硝化速率分别为-2．78N·kg-1·30d-1和-3．69mgN·kg-1·30d-1。从实验结果看，在30d的培养过程中，NH4－N消耗较多，导致硝化速率大于氮净矿化速率。

Using the buried-bag method we measured nitrification and net N mineralization rates for soils (0~ 10cm) under a variety of forest types in Xishuangbanna, Southwest China in July of 1998. The forest types studied were: tropical seasonal rainforest, Melettia leptobotrya secondary forest, forest gap, and slash-and-burn agricultural land.Net N mineralization rates were 6. 55 mg N·kg-1. 30d-1 in seasonal rainforest and 6. 37 mg N· kg-1. 30d-1 in secondary forest. Nitrification rates were 16. 28 mg N· kg-1. 30d-1 in seasonal ralnforest, 16. 38 mg N· kg-1· 30d-1 in secondary forest. Nitrification and net N mineralization rates were -2. 78 mg N·kg-1. 30d-1 and - 7. 85 mg N· kg-1· 30d-1 in forest gap, -3. 69 mg N· kg-1· 30d-1 and - 10. 69 mg N· kg-1· 30d-1 in agricultural land, respectively. Ammonification rates were negative in all the studled sites, with the result that net N mineraliza tion rates were lower than nitrification rates.