亚热带马尾松人工林的降雨截留作用

A RESEARCH ON THE EFFECTS OF ARTIFICIAL MASSON PINUS FOREST ON RAINFALL PARTITIONING IN SUBTROPIC HUMID AREA

本文通过分别实测降雨过程中林外降雨、林内降雨及树干截流的变化,分析了不同降雨量、降雨持续时间、前期降雨等因素的影响,讨论了马尾松人工林地内雨量分布的变化特点,并提出了计算模式。统计分析结果表明,林内雨和树干流只有当降雨分别到达1.6mm和4.32mm的情况下才出现,其总量分别占林外降雨的75％和4.3％,并以面源和点源的形式输入流域。此外,还阐述了降雨过程中林地内营养元素的输入及循环过程的特点。

An artificial Masson pinus forest has been chosen to measure the precipitation inside and outside of the forest, as well as stemflow. The author presents characteristics and a model for the redistribution of precipitation in the research area by analysing the relationship between the intensity and duration of rainfall, and the storage in the vegetation. The experimental spot is located on a small hill in the campus of Zhongshan University. Guangzhou. China, with an average annual temperature of 21.8°C and an average annual precipitation of 1 500 mm. The height of pines there were about 20 meters with the diameter of 30 cm. Three automatic rain gauges were set to monitor precipitation, throughfall and stem-flow respectively. Changes of soil water and water table were measured with the tensiometers and piezometers. The soil in the experimental spot is typical red soil with some content of clay. The hydraulic conductivities change greatly in space, and decrease with the distance from trees around which many cracks were found. Water table changes from two to three meters in depth. Partition of precipitation and infiltration p bcesses was taken as an integral form. Interception loss was also described as evaporation. The remain part of water was divided into two parts, throughfall and stemflow. The results show that through-fall and stemflow can only be observated when the rainfall is more than 1.6mm and 4.32 mm respectively. As a whole, throughfall source is as large as about 75 percent of rainfall, and stemflow about 4.3 percent of rainfall. In fact, throughfall can be considered as a non-point source over the whole watershed and stemflow as a point source to recharge the watershed. The throughfall can recharge the basin by infiltration. However stemflow enters the basin directly through pipe alone the roots of trees. By field surveying, those pipe can transmit the water so rapidly into the ground that no overland flow was found in the research area. The redistribution of precipitation and heterogeneity of soil hydraulic conductivity have great effects on the processes of water entering the field. From the analyses above, it can be concluded that the existence of forest causes the redistribution of precipitation and heterogeneity of hydraulic conductivity in the field, and the comprehensive effects were not only on the variations of space and time for the water recharging in the field, but also on the migration processes for mutrients.