西双版纳不同热带森林下土壤铵态氮和硝态氮动态研究

用顶盖埋管法(Close-Top Tube Incubations)就西双版纳3种热带森林（热带季节雨林、片断热带雨林、橡胶林）研究了土壤铵态氮（NH４-N）和硝态氮（NO３-N）以及土壤氮素矿化速率的季节动态情况。结果表明：西双版纳3种不同林型土壤NH４-N、NO３-N和氮素矿化速率均具有明显的季节性变化。NH４-N以干热季（4月末）最高（平均为26.92 mg*kg－1）和干季（2月末）最低(平均为12.01 mg*kg－1)；NO３-N则以雨季中期（7月中旬）最高(平均为8.9 mg*kg－1）和干季（2月末）最低(平均为4.04 mg*kg－1）；矿化速率则以干热季（(2月末～4月末)最高(平均为0.496 mg*kg－1*d－1），以雨季（7月中旬～11月初）最低(平均为0.0037 mg*kg－1*d－1）。就不同林型而言，季节雨林年均氮矿化速率(0.319 mg*kg－1*d－1)>片断热带雨林(0.25 mg*kg－1*d－1)>橡胶林(0.074 mg*kg－1*d－1)。

VARIATIONS OF SOIL NH4-N, NO3-N AND N MINERALIZATION UNDER DIFFERENT FORESTS IN XISHUANGBANNA, SOUTHWEST CHINA

Variation in NH４-N , NO３-N and N mineralization was investigated under three different tropical forests in Xishuangbanna (tropical seasonal rainforest, fragmented tropical rainforest and rubber plantation) using the Close-Top Tube Incubation method. NH４-N, NO３-N and N mineralization exhibited significant seasonal variations. The mean values of soil NH４-N were the highest (26.92 mg*kg－1) in the dry-hot season (about April) and the lowest (12.0 mg*kg－1) in the dry season (about February); NO３-N was the highest (8.9 mg*kg－1) in the mid-rainy season (mid July) and the lowest (4.04 mg*kg－1) in the dry season; Net N mineralization rates were the highest (0.496 mg*kg－1 *d－1) during the dry and dry-hot seasons (February-April) and the lowest (0.0037 mg*kg－1*d－1) during the mid-rainy season and at the end of the rainy season (July-November). Annual net N mineralization rates in the three forests were ranked: tropical seasonal rainforest (0.319 mg*kg－1*d－1)>fragment tropical rainforest (0.25 mg*kg－1*d－1)>rubber plantation (0.074 mg*kg－1*d－1).