| At present,many countries and regions are faced with the lack of water resources.With the developing of population, economy and society,the need of water is increasing more and more.But,because of the climate changing and the wasting, polluting of the water in the world/the water can be utilized is hard up.The contradiction of need and supply of water is standing out. The regulation of water requirement of plants should be researched, and the plants which need less water to grow should be developed. In that way, the problem of water lacking in the process of vegetation restoration can be resolved. So, the mensuration and calculation of transpiration and evaporation of plants are now the keystones in plant physiology. These researches are important to agriculture, forest and fruit tree in the aridity and half- aridity area in our country.Evapotranspiration is the important and complex process in watercirculationof the earth's surface,and it is the sum of the earth's surface evaporation and the plant transpiration,There are many kind of measuring methods to measure the evapotranspiration of plants now,but they are not perfect.Every measuring method is build by the study object or the study purpose.The measuring methods can not be compared firsthand. At present,not a measuring method can satisfy all measuring-demands.So,when we select the measuring methods,we must consider synthetically the scale of space and time,the measuring precision we need,the expenditure of measuring and the condition of technique,and so on.In this paper,we introduce the dominating measuring methods of evapotranspiration of plant roundly and briefly,and review the primary academic elements,merit and disadvantage,applicability and localization of all methods.In this study, the sap flow sensor which is made by the principle of stem-heat-balance of the technique of heat was used to mensurate the sap flow in the stem of plants.The sap flow in the stem of plants can indirect reflect transpiration rate.And the entironmental factors which are correlational to transpiration of plants were mensurated synchronization.In the study,the plant-circadian-measure-system named Phytalk which is produced by the company of Phytech in Israel was used to measure sap flow and entironmental factors.The plants were studied which are in common use of afforestation in Shandong province were supplied by academy of sciences of forest.The disciplinarian of daily changing of sap flow of plants , the disciplinarian of sap flow of plants in rapid growing season and the response of sap flow of plants to entironmental factors were studied.To supply theoretics basic to the study of disciplinarian of water need and supply of plant, validating the steps of water saving and withstand water lack,and the vegetation resume of specifically area.The result showed, The sap flow rate represented correspondingly consistent rhythm on the whole. In the night the sap flow rate kept at a low level, after dawn, it entered the fast increasing period, and reached the peak at noon, then came into the fast degressive period, at dusk it entered the period in which the sap flow rate is low. Simultaneity, the sap flow rate represented a difference between different species, especially at the startup time,reach peak time, tranquilization time and lasting time of tiptop rate of sap flow. And the average time of startup time,reach peak time, tranquilization time and lasting time of tiptop rate of sap flow of the same species in different months is different. The ANOVA analysis and F-test which is with plant kind as the variable to grouping,to study the day change of sap flow , F (3,572) =58.411,P=0.0000<0.01,the result showed,the day change of sap flow of different plants were mighty different. In the whole fast growing season, the sap flow change of the four kinds of plants represented difference between species, the size and the range of cycle displayed discordantly. The differences of change of sap flow between every a period of ten days were all tarnal marked.The shapes of day after day change curves of sap flow day-by-day were radical sameness,but the peaks were very different. The startup time,reach peak time, tranquilization time of sap flow were different too. Sensitivity of the plants which were studied to every environmental factor was inconsistent.Wind speed was not marked correlation with sap flow of all plants that were studied other than Platycladus orientalis(Linn.) Franco.Air humidity was marked minus correlation with sap flow of all plants that were studied.Leaf temperature and air temperature were marked correlation with sap flow of all plants that were studied. Solar radiation was marked correlation with sap flow of all plants that were studied besides Robinia pseudoacacia Linn, and Amorpha fruticosa Linn.The correlation between soil moisture and plants was complex,it was different between different plants,which was exclusive,correlation and minus correlation, correlation of distinct and inapparent were all exist. At last,the analyse of step by step multiple regression between plants that were studied and entironmental factors was carried through,and set up corresponding regression equation:Platycladus orientalis(Linn.) Franco:Sf=0.765+0.00089*Sr-0.0059*Ah-0.033*Lt+0.0052*Sm+0.016*AtArmeniaca sihirica (Linn.) Lam.:Sf=-0.202+0.0013*Sr-0.0107*Ah+0.028*Sm-0.051*Lt+0.0339*AtGleditsia sinensis Lam:Sf=-0.815+0.00091*Sr+0.0152*Sm-0.0025*Ah+0.0247*At-0.020*Lt-0.0058* WsDiospyros lotus Linn.:Sf=-2.951+0.0014*Sr+0.086*At-0.0458*Lt+0.00413*Ah+0.036*SmIn the equations: Sr is solar radiation,At is air temperature,Ah is air humidity,Ws is wind speed,Sm is soil moisture,Sf is sap flow.
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