Study On Sap Flux Density Characteristics Of Apple Trees In Gully Region Of Loess Plateau

The sap flux density is an important process driving the surface water cycle.In this paper,through the determination of apple sap flux density and the comparison of environmental factors in the main growing season(April-September)of the apple orchard in the loess gully region,combined with the soil water characteristics,the water in the apple orchard in the loess gully region of Shanxi Province was studied.Using the characteristics,the main findings are as follows:(1)Characteristics of environmental factors in the test areaThe total rainfall in the test area(April-September)was 366.4mm,and the maximum values of solar radiation,net radiation,atmospheric water deficit,potential evapotranspiration and atmospheric relative humidity occurred in June.The soil mechanical composition of the apple orchard in the experimental area is mainly composed of clay and powder particles,and the water-stable aggregates are mainly small aggregates and microaggregates.The average content of SWC(0-100cm)from April to September was 13.6%,14.0%,14.3%,15.39%,15.41%,13.4%.(2)Changes of apple sap flux density at different time scalesThe overall sap flux density of apple stalks in June was changed from June to May>September>July>August>April,and the daily variation of the typical sunny days from April to September was a single-peak curve.The sap flux density is as follows:sunny>cloudy>rainy.The sap flux density exhibits a significant circadian rhythm during the day and night.The order of the liquid flow rate in each month is September>April>April>June>May>July.(3)Correlation analysis between apple sap flux density and environmental factorsThere was a significant positive correlation between Js and meteorological factors VPD,Ta,Ws,PY,Rn and soil factor SWC.There was a significant negative correlation between Js and RH,while PY,Rn,VPD and RH were the most closely related variables of Js,Js.The correlation coefficients are 0.789,0.783,0.619 and-0.482,respectively.Under typical weather conditions,the correlation coefficients were 0.95,0.84,0.72,and-0.57,respectively.