摘要
用小流域集水区和物质平衡方法 ,于 1999年对西双版纳热带季节雨林生态系统的氮素循环进行了初步研究。西双版纳季节雨林生态系统的氮库总储量为 6 4 81.2kg·hm-2 ,其中活体生物量、凋落物层和土壤 (0～ 30cm)中的氮储量分别为 970 .9、37.7、5 4 81.2kg·hm-2 。土壤中的氮占生态系统氮总储量的 84 .4 % ,活体生物量占 15 .0 % ,凋落物层仅占 0 .6 %。结果表明季节雨林的氮主要分布在土壤中 ,而在生物量中只占很少部分。大气降水、林内穿透水、树干流及地表径流的氮含量分别为 0 .5 6 5、0 .82 8、0 .983和 1.0 4 2mg·dm-3 ,氮通量则分别为 8.89、10 .97、3.5 7、5 .95kg·hm-2 ·a-1。大气降水输入氮 8.89kg·hm-2 ·a-1,径流输出氮 5 .95kg·hm-2 ·a-1,收支平衡 (输入—输出 )为2 .94kg·hm-2 ·a-1。氮的生物循环 :吸收为 14 9.86kg·hm-2 ·a-1,存留为 6 9.30kg·hm-2 ·a-1,归还为 80 .5 6kg·hm-2 ·a-1,循环系数为 0 .5 4。结果表明未受干扰的季节雨林生态系统处于氮积累的状态 ,有利于该生态系统的稳定与持续发展。
Xishuangbanna, located in southwest China, bounded by Laos and Myanmar on the upper Mekong River, is on the northernmost edge of tropical Asia. As a result, a mosaic distribution of tropical seasonal rain forest, which mainly appears in the wet valleys, usually with small streams or on the low hills and flats below 1000 m altitude exists in Xishuangbanna. The tropical seasonal rain forest in Xishuangbanna is rich in species and has a complex forest canopy and structure. In 1999, 119 species with DBH>10 cm were recorded in the 1 hm2 study plot. Based on the 'small catchment' approach and input-output budgets, we studied on the nitrogen cycling in the seasonal rain forest. The nitrogen stock in the seasonal rain forest ecosystem (6 481.2 kg·hm -2) was higher than that of montane rain forest in Hainan of China (6 345 kg·hm -2), but lower than montane rain forest in New Guinea (20 190 kg·hm -2), lowland rain forest in Brazil (7 537 kg·hm -2), and lowland rain forest in Ghana (7 230 kg·hm -2). The distribution of the nitrogen stock in the seasonal rain forest ecosystem is as follows: 970.9 kg·hm -2 (15.0%) in the living biomass, 37.7 kg· hm -2 (0.6%) in the forest floor, and 5 481.2 kg·hm -2 (84.4%) in the soil (0-30 cm). We found that most of the nitrogen in the seasonal rain forest was stored in the soil, but not in the living biomass. Soil (0-10 cm) net nitrogen mineralization rate was 90.4 kg·hm -2·a -1. Soil played a very important role of stocking and providing N to plants. The nitrogen content in precipitation, throughfall, stemflow and stream flow were 0.565, 0.828, 0.983 and 1.042 mg·dm -3, respectively. The nitrogen input from precipitation, throughfall and stemflow were 8.89, 10.97 and 3.57 kg·hm -2·a -1, respectively. The nitrogen output in stream flow was 5.95 kg·hm -2·a -1. The nitrogen net increase in the seasonal rain forest was 2.94 kg·hm -2·a -1. In the nitrogen biological cycling, 149.86 kg·hm -2·a -1 was taken up by plants,69.30 kg·hm -2·a -1 stored in living biomass,and 80.56 kg·hm -2·a -1 returned to soil. This undisturbed seasonal rain forest had the nitrogen conservation mechanism and remained in the nitrogen accumulation state.
出处
《植物生态学报》
CAS
CSCD
北大核心
2002年第6期689-694,共6页
Chinese Journal of Plant Ecology
基金
国家自然科学基金 (4 0 173 0 3 9)
云南省自然科学基金 (97C0 17R
2 0 0 1C0 0 64M)
中国生态系统研究网络 (CERN)及中国科学院知识创新工程项目资助
