Transpiration Characteristics Of Natural Stand Of Larix Gmelinii And Its Response To Environmental Factors

As one of the important water consumption pathways in forest ecosystems,stand transpiration is of great ecological significance for elucidating the mechanism of environmental conditions regulating stand transpiration and the regulation of regional water cycle by analyzing its changing characteristics and its response to environmental factors.In this thesis,the thermal technology method and the scale expansion method are used to calculate the transpiration of th Larix gmelinii stand,and analyze its variation characteristics under different time scales and different weather conditions.Correlation analysis,factor analysis and partial regression coefficient calculation were carried out between factors and stand transpiration.the result shows:(1)On the daily scale,the trunk sap flow density of Larix gmelinii starts at about 03:00and stops at 20:00.The environmental factors that affect the change of Larix gmelinii trunk sap flow density are net radiation and soil temperature.On the monthly scale,the trunk sap flow density of Larix gmelinii reached the maximum value in mid-July;soil factors are the main environmental factors affecting the trunk sap flow density of Larix gmelinii.Under different weather conditions,the trunk sap flow density of Larix gmelinii on non-rainy days was greater than that on rainy days,and the trunk sap flow density increased significantly after rainfall.(2)On the monthly scale,the variation range of transpiration of Larix gmelinii stands was 0.47-1.44 mm/d,reaching the maximum value in mid-July.On the daily scale,stand transpiration started at 01:00 and reached a peak value of 0.15 mm/h around 14:00.Under different weather conditions,the stand transpiration showed that the non-rainy days > the rainy days,and the stand transpiration increased significantly after the rainfall.The changes of stand transpiration,net radiation,and water vapor pressure deficit have an obvious time lag effect.(3)Air temperature,relative humidity,potential evapotranspiration,trunk temperature,soil temperature at different layer depths,net radiation,and photosynthetically active radiation are the main environmental factors that affect the transpiration of Larix gmelinii stand.Among the transpiration driving factors,the dominance rate of the environmental factor that dominates the transpiration of the stand is: soil temperature(52.4%)> net radiation(29.5%)> relative humidity(18.3%);among the temperature change factors,the dominance rate of the environmental factor that dominates the transpiration of the stand It is: soil temperature(51.1%)> air temperature(39.2%)> trunk temperature(9.7%).When the soil moisture condition is sufficient,the transpiration of Larix gmelinii mainly uses the moisture of the 0-10 cm soil layer.When the soil is relatively dry,the Xing’an larch mainly uses the moisture of the 20-80 cm soil layer.