| In this article,Ginkgo biloba L.Sap flow and water consumption had been selected as entry point,to acknowledge the regulation of Ginkgo water consumption and water transportation time variation,to conclude environmental factors which affecting the sap flow of the Ginkgo.The model between Environmental factors and velocity of sapwood flow has been established and proved,to comment the ability of Ginkgo water consumption,in order to provide the theoretical for the scientific fields irrigation,the main conclusion is below:The daily variation of sap flow velocity has the single peak and multi peak curse.The sap flow velocity was significantly different at different heights,and directions of the trunk,sap flow velocity at the upper position of the trunk is higher than the lower position,and also showed sap flow velocity of the south was the most and the north was the least among the different directions.The sap flow velocity was significantly different in different weather,In three typical weather,the law of sap flow velocity is as follow:sunny>cloudy>rainy,The daily cumulative flux is the same as sap flow velocity.The starting time of sap flow velocity in sunny day was earliest than the other weathers,the stopping time was latest,it starts at AM 6:00 while stops at 20:00 during a day.If the season been considered for the diurnal variation,the starting time of sap flow velocity in summer was earliest than the other seasons,it starts at 6:00;auturm was latest,it starts at 9:00.The peak of sap flow velocity appears earliest in autumn at 11:00,and that appears latest in summer at 11:00;The stopping time of sap flow velocity appears earliest in autumn at 20:00,but it decreases to zero at PM 24:00 in spring and summer;the sap flow velocity and daily mean value of sap flow velocity in auturm is lower than spring and summer,with the 78%of the spring and summer.The peak of the sap flow velocity is 68 cm/h in June.The sap flow is start at beginning of April,close at beginning November,it has synchronous change with LAI.The daily cumulative flux is arrived the max 20.5L/d in June,and decreasing at Autumn obviously.The max of the monthly cumulative flux appears at June with 331.5L.The law of cumulative flux is as follow:Spring>Summer>Autumn.During the grow season of single Ginkgo from April to October,the total water consumption is 1693.7L.In the typical sunny day,Ginkgo sap flow velocity,photo synthetically active radiation(PAR),vapor pressure deficit(VPD),wind speed(W),soil water(REW)have the synchronous variation trend,but in the rainy day,sap flow has little relation with the W and VPD,which is slower than sap flow velocity.If long time is considered,the peak of the sap flow velocity is decreased by the reducing of REW.If the significant of the environmental factors been considered,PAR>VPD>W,REW is not relate to sap flow.Ginkgo sap flow has the liner regression relation with the PAR,VPD,W,obvious regression is pretty especially in 95%Confidence interval.After proved,equation simulation in Sunday is better than cloudy and rainy,with the 2.89%-23.12%error rate,for some application value.Based on REW,PAR,VPD,W,the response relationship between sap flow and environmental factors were analyzed,the results showed:The effects of soil moisture on sap flow were restricted with specific threshold value.When the relative extractable soil water REW was higher than 62%,soil moisture was unlimited to sap flow of G.biloba.While when REW was lower than 62%,soil moisture was a limiting factor for sap flow,and the relationship between sap flow and soil moisture can be described by half value empirical functions.PAR was the driving factor for sap flow,with the driving effect being stronger when PAR was lower than 0.39 mmol·m-2·s-1,while it reached saturation when PAR was higher than 0.8 mmol·m-2·s-1.The relationship between sap flow and PAR could be described by hyperbolic functions.Vapor pressure deficient's function to sap flow was dual,when VPD was lower than 3.2 kPa,it had driving effect and the relationship between them could be escribed by hyperbolic functions.While VPD was higher than 3.2 kPa,it was restricting functions which can be described by negative linear functions.Wind was a restricting factor for sap flow,but it worked only when wind speed was>4 m second.The relationship between sap flow and wind speed could be described by half value empirical functions. |
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