Study On Transpiration Characteristics Of Major Tree Species In Loess Plateau Of West Shanxi

Aiming at water consumption of trees construction and the using of water resources, daily and seasonal changes of transpiration rate of 8 kinds of shurb trees and 9 kinds of economic trees species, sap flow velocity of 4 kinds of trees species for soil protecting in Semi-arid Area and the major determinant factors were studied by using the method of rapid weighting and Thermal Dissipation Probe considering planting-configuration and water using and the SPAC theory of Semi- arid Area in Loess Plateau of west Shanxi. Fitting models of transpiration rate and meteorological factors,the estimated total water consumption used for tree transpiration and the dominant environmental factors influencing sap flow velocity were concluded.1. The diurnal variation of leaf water content and leaf water potential were a waveform curve and the former was higher in the morning and evening than at noon, the minimum lowest point of the latter was between 10:00 and 14:00 for shurb and economic trees. The relationship between leaf fresh weight and leaf area can be fitted by exponential curve, and the relationship between leaf fresh weight and diameter can be fitted by different fuction of tree species.2. Diurnal changes of transpiration rate of different species could taked on " single peak" and " double peak" curves; The tree species had the average transpiration rate in the following orde: V. Rhytidophyllum>R.crataegifolius>S.oblata>S. trilobata> O. davidiana> C. alba> L. japonica> F. suspens.3. Leaf water potential and transpiration were negatively related, and their relationships can be fitted by logarithmic curve. The bigger of absolute value of regression coefficient for Logarithmic function, the more lossing water transpiration rate,the weaker trees drought.4. Sap flow velocity (SFV) of R. pseudoacacia,P. tabulaeformis,Q. liaotungensis and P.davidiana exhibited diurnal patterns and the curves take on single peak and Quasi-single peak; the time of daily SFV maximum values was different in different days.5. The forecast suggests that the estimated total water consumption used for tree transpiration for R. pseudoacacia was much higher than that of other tree species over the whole growing season (272.89 mm,266.46 mm,131.26 mm and 311.31mm, respectively).6. Diurnal changes in sap flow were closely related to changes in environmental variables, but the dominant environmental factors differed between the species. Soil moisture and water vapor pressure deficit were the governing factors for Robinia pseudoacacia, solar radiation and soil moisture were mastering factors in Pinus tabulaeformis SFV, air temperature and solar radiation were the main factors influencing diurnal changes in Q. liaotungensis SFV, whereas solar radiation and water vapor pressure deficit were the principal factors for P. davidiana. A statistical model to calculate SFV from micrometeorological data is provided.