西双版纳地区热带季节雨林与橡胶林林冠水文效应比较研究

Comparison research on hydrological effect of the canopy of the tropical seasonal rainforest and rubber forest in Xishuangbanna, Yunnan

季节雨林和橡胶林是西双版纳热带森林系统中可以代表原始林和大面积种植的人工林两种林型 ,采用水量平衡法 ,利用对以上两种林分林冠水文各分量 1 996～ 2 0 0 1年的观测结果 ,初步分析其林冠水文效应 ,结果表明 :一年内 ,季节雨林林冠截留量 660 .6mm,树干径流量 80 .7mm,穿透降雨量 ,85 3.2 mm,分别占同期降雨总量的 41 .43%、5 .2 4 %、5 3.74% ;橡胶林林冠截留量 393.5 mm,树干径流量 1 0 4 .1 mm,穿透降雨量 1 0 96.8mm,分别占同期降雨总量的 2 4 .68%、6.68%、67.85 % ;两种林分森林水文各分量干、雨季差异显著 ;在研究中还发现 ,季节雨林中树干径流量随径级的增大而减小 ,干季出现密林 (季节雨林 )的穿透降雨量大于疏林 (橡胶林 )的反常现象 ;与我国其他地区相比 ,季节雨林和橡胶林有较大的林冠截留率及干流率。

The Region of Xishuangbanna is located in the north edge of the distribution of tropical rainforest in the world, and it has remarkable seasonal climate variations which is different from tropical rainforest in other regions. In Xishuangbanna, the canopy of rubber forest (Hevea brasiliensis) plantation often form a single layer structure that is different from the multiplayer canopy found in natural tropical seasonal rainforest. The objective of this research is to compare and quantify the hydrological characteristics of rubber forest and natural tropical seasonal rainforest canopies. The experiments were conducted in the rubber forest plantation in Xishuangbanna ( 21°56′N, 101°15′E ). Based on six-years observation from 1996 to 2001, it was found that the canopy interception, stemflow and throughfall of tropical seasonal rainforest were 660.6, 80.7 and 853.2 mm per year, which account for 41.43%, 5.24% and 53.74% of the total rainfall respectively. In rubber forest plantation, the canopy interception, stemflow and throughfall of rubber forest were 393.5, 104.1 and 1096.8 mm per year, which account for 24.68%, 6.68% and 67.85 % of the total rainfall respectively. The stemflow of tropical seasonal rainforest decreased with the increased of diameter at breast height of the trees. The proportions of canopy interception, stemflow and througfall of two types of forests also had great differences between dry (from Nov. to Apr.) and rain (from May to Oct.) seasons. The curve of canopy interception of tropical seasonal rainforest was found to be a reverse “V”. The percentage of rain being intercepted decreased as the total rainfall increased. The curve of canopy interception of rubber forest during a typical year formed “M”, and the rate of interception decreased as the rainfall increased from Feb. to Sep. while no clear regularity during other months in the year. During dry seasons, the amount of throughfall of tropical seasonal rainforest (with complex structure) was found to be greater than that of rubber forest plantation (with simple structure). It was probably owing to great amount of dew and fog water in try seasons in this region.In summary, the canopy the tropical seasonal rainforest intercepts much greater amount of water during rain season, especially in July, when the monthly precipitation account for more than half of the annual precipitation. Compare with other regions in China, both tropical seasonal rainforest and the rubber plantations in Xishuangbanna have much higher canopy interception and stemflow rates.