Studying On The Relation Of Trees Transpiration Process And Environment Factors In Semiarid Zone, Losses Plateau

Semiarid region in Losses zone is the typical fragile area, in this region, moisture is the key factor to limit the vegetation restoration and reconstruction. In this paper, considering arid and semiarid scarce water resource, and unreasonable plant population density, based on the SPAC theory and field observation, the changing characteristics of plant transpiration, environment factors and physiology factors were systematically and quantitatively analyzed, and the major factors affected transpiration were determined by analyzing the relation of transpiration and environment factors.The four major afforestation plants used in semiarid region in Losses zone (Pinus tabulaeformis, Robinia pseudoacacis, Hippophae rhamnoides, Populus bolleana) were selected, in plant growing season (May to Oct.) in 2005, LI-6200 portable photosynthesis system, Li-1600 Steady State Porometer, HOBO automatic weather station were applied in observation of the samples'weight, soil moisture, seedling water consumption by transpiration, and transpiration and photosynthetic rate.. the main conclusions were listed as follows:The transpiration characteristics of sample trees are, including the diurnal process, seasonal process, and the effects of moisture on daily transpiration, the transpiration velocity is: Hippophae rhamnoides> Robinia pseudoacacis>Populus bolleana> Pinus tabulaeformis, and usually occurred unimodal curve with the highest at noon and lowest in morning and evening, however, sometimes occurred double-humped curve in the condition of meteorological phenomena and soil moisture changing.Stoma resistance pressure changing characteristics and its relation to environment factors were studied. The diurnal value is: Pinus tabulaeformis > Populus bolleana> Robinia pseudoacacis> Hippophae rhamnoides in the serious menacing of moisture (water content 6.2%), and Pinus tabulaeformis > Populus bolleana> Robinia pseudoacacis in water content of 6.2% and 25.6%.The study on the relation of transpiration rate and leaf water potential showed that transpiration rate of Populus bolleana is significantly correlated with leaf water potential in middle and high moisture gradient.The study on the effects of environment factors on transpiration rate indicted that transpiration rate is significantly correlated with temperature, effective radiation and...