南亚热带季风常绿阔叶林水文功能及其养分动态的研究

HYDROLOGICAL FUNCTION AND NUTRIENT DYNAMICS IN LOWER SUBTROPICAL MONSOON EVERGREEN BROAD-LEAVED FOREST

根据在鼎湖山季风常绿阔叶林集水区3年的观测结果，对这一南亚热带地带性植被的水文功能进行了较深入的探讨。由于林分结构复杂，季风常绿阔叶林对大气降水具有较高的林冠截留率，截留率的季节变化动态与降水量的季节分配有关。该森林土壤结构良好，其渗水速度快，加上有较厚的枯落物层，对于减缓地面径流，减少水土流失，功效甚大。但由于土层较薄，其蓄水功能有限。该森林的径流量占总降水量的比例特别是地表径流所占比例较小，分别为50．22％和14．19％。其季节分配有利于保持水土和植物生长。由于土壤蓄水量变化出现负值，用水量平衡法计算得出鼎湖山季风常绿阔叶林年蒸发散量为1323．98mm，占大气降水量的51．81％。该森林的降水中主要营养元素浓度较高，降水带来大量的养分，特别是氮素的年输入量高达35．29kg·hm-2。淋溶也给该森林带来较高的养分归还量，其中钾的淋溶量高达35．65kg·hm-2；镁的淋溶量高达8．9kg·hm-2，为林外雨输入的2．37倍。径流中的氮输出为28．35kg·hm－2，降水中的氮素净输入量为6．94kg·hm-2；但镁的净输入呈负值。

The hydrological function of monsoon evergreen broad-leaved forest of Dinghushan Biosphere Reserve was studied using rneasured hydrological factors. This forest has high canopy interception as a result of its complex structure, with seasonal changes varying with the distribution pattern of precipitation. The soil of the forest has a high capacity for water conservation and shows a good texture. Total runoff, especially surface runoff, accounts for a lower proportion of total precipitation. Its seasonal distribution is a function of variation in water conservation and utilization. The volume of evapotranspiration is 1323. 98mm, or 51. 81 % of total precipitation. The nutrient input of rainfall is higher than most of other forests, especially the total N input, which reaches 35. 29kg·hm-2. The higher nutrient concentration in throughfall indicates strong leaching from the canopy. The large difference between the nutrient input from rainfall and output from runoff indicates a high level of nutrient conservation in this forest.