Study On Multi-scale Water Consumption Of Caragana Microphylla In Horqin Sandy Land

In this paper,the photosynthetic parameters and environmental factors of the leaf of Caragana microphylla in Horqin sandy land were measured by the photosynthesis meter,and the response of Caragana microphylla to natural drought stress and the mechanism of photosynthesis（P_n）regulation were explored,and the mechanism of drought resistance and its adaptation strategies to adversity were discussed.We measured transpiration and evapotranspiration of Caragana microphylla with packaged sap flow gauges and an eddy covariance system.In contrast,the characteristics of transpiration（T）and evapotranspiration（ET）,and water budget of the community were analyzed in detail.The characteristics of plant sap flow under extreme soil moisture and temperature conditions were analyzed,and the physiological and ecological characteristics under plant stress conditions were explored.In this paper,transpiration water consumption characteristics of Caragana microphylla were studied at three different scales.The main research results are as follows:（1）on the leaf scale,at the diurnal changes,in July 5,Pn has a midday depression phenomenon;at the month changes,P_n has two peaks form a valley in the whole growing season,the peak value appeared in June and September and the trough appeared in the year of July,this is related to the continuous drought in the study area;Caragana microphylla appeared second flowering phenomenon in September,which may be related to the drought and compensation effect after water.（2）on the single branch scale,the rate of flow rate of the branched liquid with different basal diameters is basically the same.The stem flow rate increased with the increase of basal diameter.The effect of temperature on stem flow rate was higher than that of water,and the rate of stem flow rate was higher than that of low temperature.（3）on the stand scale,the daily changes of T and ET of Caragana microphylla community were basically consistent,the daily mean values were1.61mm·d^-11 and 2.43mm·d^-1,respectively;the daily variation curves of T and ET were wide and single peak type and clock type,and the daily accumulative process curves showed a"S"type growth trend;in different weather conditions,the peaks of T and ET daily changes were different.The change level of total amount is higher than that of cloudy and rainy days;in different precipitation events,the rainfall time varies lead to T start time or end time changed,there is no significant difference of ET occurrence time before and after rainfall;when P≤10mm or P>20mm,T has decreased after rainfall,10mm<P≤20mm,T significant improve after rainfall;in different rainfall intensity,the peak and total amount of ET increased after rainfall,and the ET peak value was positively correlated with rainfall.ET/P is 1.04,water budget of the Caragana microphylla community is nearly balance.