Study On Characteristics Of Sap Flow And The Relationship With Environmental Factors In Plantation Of Haloxylon Ammodendron

Transpiration is the main way form of plant water consumption characteristics,and play an important role in the SPAC system. In order to further understand the ruleof supply water, the variation of the sap flow and the response of plants toenvironmental changes plants in desert area. This study selected three sample plotsnear the Aziz Akzo River in Ebinur Lake Wetlands Nature Reserve. Choose threeHaloxylon ammodendron which growing well, straight trunk, no pests as the researchobject. Under natural conditions, using Probe12make a continuous observation tomeasure sap flow. And simultaneously measure micrometeorological factors (airtemperature (Ta), relative humidity (RH), wind speed (WS), etc.), soil factors (soilmoisture, soil water potential, soil temperature, etc.) and photosynthetic physiologicalindicators (transpiration rate, net photosynthetic rate, stomatal conductance, etc.).Make an analysis to the rule of variation characteristics of sap flow of H.ammodendron in every plot. To explore the mechanism of transpiration waterconsumption, and also explore the rule tree of sap flow response to environmentalfactors. The results are as follows:(1) The diurnal variation trend fluctuations of sap flow of H. ammodendron basicis very similar, showing a significantly high daytime and lower night rhythm, having aunimodal or multimodal in daytime, keeping a lower value in night, even zero, atnoon the sap flow exist “noon break” phenomenon. The diurnal variation of sap flowmain show bimodal lattice in plot1(Diameter at breast height (DBH) is6.85cm), andpresent a single peak in plot2(DBH is9.55cm) and plot3(DBH is15.92cm). Butbecause environmental factors and their own physical condition are different, the startand end of sap flow are different, and also the time of peak flow and flow rate aredifferent.(2) The roots of different diameters are affected by common environmentalfactors, having a same fluctuation trend. Different diameters, sap flow rate is also slightly different, the sap flow rate of the stem of big diameter is higher, is moreaffected by environment factors, its fluctuation change is more obvious, and the gap isnot large at night, its value are relatively low. With the increase of flow rate, the gapwill be more and more larger. The fastest sap flow rate, the gap is maximum. The sapflow rate and diameter have a significant correlation, the big diameter has a faster sapflow rate. The average flow rate of a maximum diameter of9.5mm is187.58g/h，theminimum diameter, its sap flow rate is14.30g/h.(3) Within a certain range, temperature is warming, the sap flow rate accelerate,otherwise decline. A maximum of air relative humidity in the early morning hours, theminimum occur when the highest temperature exist in the afternoon. When therelative humidity is low, the flow rate will be accelerated; when relative humidity ishigh, the flow rate will be reduced. In general, the changes tend between wind speedand flow rate to be consistent. The influence factors of sap flow rate are: Ta＞RH＞WS, the sap flow rate and air temperature have a significant positive correlation(P<0.01), the sap floe rate and air relative humidity have a significant negativecorrelation.(4) Combined with soil conditions, soil surface water content is very similar inthree plots, range from6.5%to7.0%, soil vertical profiles0-100cm, as the change ofsoil depth, soil moisture content is increasing. Usually water potential is higher in theearly morning and evening, the maximum generally occurs at about7:30in themorning, indicationg that H. ammodendron suffering drought stress level will besmall; water potential is lower at noon and afternoon, incidating that plant sufferingdrought stress level and water deficit severely.(5) Soil moisture and temperature have an effect on the sap flow. Soil moisture isthe "source" of sap flow activity, soil temperature has a very important impact on theeffectiveness of the soil moisture, it determines the water absorption capacity andphysiological activity of roots.Namely, soil temperature is not the direct factors that affects the flow activity, but have an important impact on sap flow.(6) During the data observation, the trend of leaf water potential of H.ammodendron have a substantially same change, almost present bimodal, leaf waterpotential is relatively high in the early morning and evening, and is instantaneouschange. Sap flow rate and soil temperature have a significant negative correlation (P<0.01). In0-100cm layer, soil water potential and sap flow rate in different soil layershave different degrees correlation. Surface temperature is high in the daytime, thesurface evaporation is big, whether in cloudy, sunny or rainy day, water potential of0-10cm are consistent, and also have a negative correlationship with flow rate.(7) Combined with photosynthetic physiological indicators of H. ammodendronin three plots, transpiration rate and net photosynthetic rate, photosynthetically activeradiation and stomatal conductance are the most influential factor, water useefficiency has a very great impact on them. Other influence factors, such as airtemperature, relative humidity and intercellular CO2affect transpiration rate. And allinfluence factors play a role with each other. Under different circumstances, differenttime periods, restricting factors will be different in the same plant.