Research On The Calculation Of Transpiration Water Consumption In Haloxylon Ammodendron Based On Heat Dissipation Probe Method

The Haloxylon ammodendron shrub plantation in the Minqin oasis-desert ectone was chose as the research material in this study,and the Granier empirical formula was corrected by the thermal diffusion correction system,Then the relationship between the sap flow and the meteorological factors was explored by the corrected Granier formula.That will be provide theoretical support for the study of water use of H.ammodendron shuttle plantation,and will provide scientific basis for the ecological restoration in dry and barren areas.The main results followed that:(1)Under different pressure of water column heights of 15,30,50,70 and 90 cm,the data which calculated by the original Granier formula were lower 31.94 ± 0.82%?30.92 ± 0.88%?30.56 ± 0.87%?32.15 ± 1.02% and 31.09 ± 1.22% than that of weighing method respectively,and the correction formula was Fd=0.0152K1.155 R2=0.9453.The sap flow density was calculated by the calibration formula is much closer to the data of weighing method than that of the Granier empirical formula,It is shown that the corrected Granier formula can makes the measurement result more accurate and reliable.(2)The daily variation of the sap flow rate in H.ammodendron exhibited single-peak curve in the typical sunny weather conditions.The sap flow of the trunk in H.ammodendron was different from the start time and the peak time in each month.The sap flow rate was usually double peak and multi–peak at rainfall,the regular changes were not observed between rainfall and sap flow rate,the sap flow rate at rainfall is lower than that in sunny days during daytime;The larger the diameter of the trunk,the greater the transpiration,the transpiration of single plant was 45.02 mm and 43.09 mm,and it account for 47.74% and 45.17% in 2016 and 2017,respectively.(3)The transpiration rate of H.ammodendron was significantly positively correlated with net radiation,air temperature,saturation vapor pressure difference,photosynthetically active radiation,but the relative humidity and transpiration rate showed a significant negative correlation.The main meteorological factors of influencing the transpiration rate of H.ammodendron are different in different years,the most important meteorological factor of affecting the transpiration was net radiation in 2016,and the most important meteorological factor of affecting the transpiration was air temperature in 2017.(4)There was an obvious time lag between the stem sap flow of H.ammodendron those of PAR and VPD,the stem sap flow was lagged behind PAR for 80 min but it was ahead of VPD for 114 min,additionally,the time lag exhibited significant difference during the growth season(from May to September);Though the sap flow of H.ammodendron was more dependent on the variation of PAR on the daily scale than VPD,but it was more closely related to VPD during the day time;The time lag between the stem sap flow and PAR/VPD was not affected by the tree factors and the nocturnal sap flow.