The Study On The Water Consumes By Water Conservation Forest In Miyun Reservoir Watershed

Miyun Reservoir is the important source of drinking water in Beijing,serving 50% of the city water consumption and 70% of the domestic water. In order to protect the water of Miyun Reservoir, the vital problem in constructing water conservation forest is to establish and manage large-scale water conservation forest in its upper reaches, to select tree species that consume less water, can purify water and can protect soil and water, and to combine these species. This paper mainly studies the water consumption mechanism of water conservation forest, to disclose water consumption characteristics and laws of different tree species, and to provide theoretical base for selection of afforestation species which consume less water and for combination of forest structure.Aiming at the main tree species in the upper reaches of Miyun Reservoir in Beijing, six tree species and representative forest stands are selected as the object. The six tree species are Pinus tabulaeformis, Robinia pseudoacacia, Populus., Ailanthus altissima, Vitex negundovar. Heterophylla and Platycladus orientalis. In the growth season of 2002-2003, with the advanced instruments and equipments such as Stem Flow Gauge, fully-automatic weather station and Dew Point Microvoltmeter, many experiments were carried out indoors and outdoors. Applying the method of regression, numerical calculation and finite element, this paper analyses the experimental data of soil water potential, individual plants and forest stands, and analyses the influence between them and the environmental factors.This paper mainly studies these following points:(1) Water consumption characteristics of the main water conservation forest;(2) Water consumption rules of representative water conservation forest;(3) SG-SPAC transmission-model of water transportation of forest;.(4) The scale-transition model of water consumption of forest. And the following results are:1. Under the condition of sufficient irrigation, tub-planting experiment has been carried out, to compare water consumption of different tree species, and the results are:The daily water consumption of Pinus tabulaeformis, Ailanthus altissima and Vitex negundovar. heterophylla is relatively low. The relationship between water consumption by forest and environmental factors is complicated:Soil moisture content is the basic factor of daily water consumption of forest, and the atmosphere temperature is its vital factor. Only when there is sufficient water in the soil, and the atmosphere temperature is high enough can forests begin to consume water, and then the other factors such as sunlight can have effect; when there is sufficient water to supply to the trees, their water consumption amount can reach themaximum. The maximum water consumption amounts are different as for different tree species. The maximum water consumption amounts of the same tree species are also concerned with leaf area and other physiological indices.2. Water consumption rules of representative water conservation forest: Concerning water conservation forest stands, this paper studies the daily change processes of stem flow of Pinus tabulaeformis and Robinia pseudoacacia under the same condition.The daily change processes of stem flow of Pinus tabulaeformis and Robinia pseudoacacia obviously change regularly, while this daily change is different concerning species and age, and the tendency in large is about the same. The maximum daily water consumption and the maximum daily water consumption rate of the seedling take place between10:00 and l4:00. The stem flows of different species are different. The daily maximum stem flow of Pinus tabulaeformis and its total amount are both smaller than those of Robinia pseudoacacia 's.The stem flow of forests is of great differences under different weather: there is maximum stem flow in sunny day, and minimum in cloudy day, and the stem flow of cloudy day is 50 percent of that of sunny day. It is steady during the night, and the water consumption amount during daytime is effected greatly by the weather. The relevance between...