| In this study, six transect sites(namely: old P. euphratica with good and badvitality, mature P. euphratica with good and bad vitality, young P.euphratica with goodand bad vitality) of P. euphratica are chosen in the national natural Populusconservation park located in the middle reaches of Tarim River based on formerscholars study method. Stem sap flow of them has been measured using heat pulsetechniques of ICT company and their diurnal sap flow change characteristics has beenanalyzed too. Using portable climate station, four climate factors has been measuredsynchronizing, by setting up the Quadratic Equation between every climate factors andstem sap flow, the correlation between them has been analyzed. With high resolutiongroundwater detecting sensors, timely shallow aquifer level has been measured, and thecorrelation between diurnal sap flow of P. euphratica in different age and vitality groupand groundwater depth has been analyzed. In order to reveal the diurnal changecharacteristics of stem sap flow of P.euphratica in different age and vitality group andcompensate water uptake data of P. euphratica in the middle reaches of Tarim River,finnaly supply with reference basis for rational allocation and utilization of waterresources.The results as follows:(1) Although P.euphratica in each plot are belong to different age and vitality group,but their diurnal stem sap flow change characteristics are almost the same: in measuringday, stem sap flow began to increase from morning with the strengthening solarradiation followed by sun rise, around13:00it reached maximum value of a day andappeared midday depression, around18:00began to decrease followed by decliningsolar radiation. But certain differences existed caused by their differences in age andvitality feature. Total sap flow of P. euphratica conducted sap flow measurement ineach plot are with following sequence: old P. euphratica with good vitality＞matureP.euphratica with good vitality＞old P. euphratica with bad vitality＞young P. euphratica with good vitality＞mature P. euphratica with bad vitality＞young P.euphratica with bad vitality.(2) With strengthening solar radiation and rising temperature, stem sap flow of P.euphratica in each plot started to increase, around13:00it reached maximum value andappeared midday depression, sap flow remained a constant value, in contrast, theshallow water aquifer is declined and also reach to a constant value around13:00, thenstarted to rise, both of them back to their initial value of the measuring day. The changeamplitude of groundwater at the site of P. euphratica with good vitality is higher thanthe site of P. euphratica with bad vitality.(3) Correlation and regression analysis showed that, impact of air temperature andhumidity among meteorological factors which impacts stem sap flow of P. euphraticawith different vitality is higher than of solar radiation and wind speed. Everymeteorological factors impact on diurnal change of stem sap flow of young P.euphratica with both good and bad vitality at the same level. Diurnal change of P.euphratica’s stem sap flow in old age group, mainly impacted by air temperature andhumidity, secondly impacted by solar radiation and due point temperature. |
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