| Lack of water is a severe problem all over the world. Vegetation and land degradation are getting more concerned. Development of vegetation restoration techniques is one important way to solve those problems. Contradiction between water requirement and supply becomes sharper. Water use efficiency of afforestation species is an urgently-solved problem. One of the basic ways to solve it is reasonably choosing species whose WUE are higher. How to calculate the efficiency of transpiration and water use is now research emphasis in plant physiological ecology. Choosing Dateplum Persimmon, Black Locust, Siberian Apricot and Arborvitae as research objects has a great meaning to vegetation restoration, mountain afforestation and city constructions in drought and semiarid areas in north of China.The WUE is important to measure the ability of water deprivation and saving. Calculating the efficiency of transpiration plays a key role to WUE measurement. Transpirations are so complicate that there are so many different measuring means on different levels. Lots of researches about how the relevant environment factors affect transpirations have been done. In this research, the sap flows of four plants and environment factors have been collected within four seasons by using the Phytalk system, in order to discover the patterns of transpirations and analyze the response to environment factors. It provides basic data and theory on water deprivation patterns, water use efficiency and vegetation restoration in certain areas.As it is showed in the results, transpiration pattern is similar to each other plant within one day. It contains five phases, which are stationary phase before dawn, rising period, acrophase, decline stage and stationary phase again after dark. Most of them are double-peak curves, the others are not. ANOVA results showed that there are differences of transpiration rates between four seasons and species. For each plant, transpiration rates in spring and summer are high than winter and autumn, and the sap flows starting time is also earlier. Arborvitae's transpiration rates in four seasons are higher than other three plants. Multiple comparison results showed that there is no difference between Black Locust and Siberian Apricot. The regression analyzing results showed that different plants are sensitive to different environment factors, as well as it is for one specie between seasons. Solar radiation is almost in every regression formula with high coefficient. Unlike the solar radiation, wind speed only appears once in the formula of Black Locust in winter, which means that whether wind speed has a significant effect on transpiration needs further discussions and researches. The statistic of sap flows starting time and solar radiation values results showed that different plants have different sap flow starting time and needs different solar radiation values to trigger sop flows. Black Locust needs the highest value 31.9120 w/m2, Dateplum Persimmon and Arborvitae need less than Black Locust as 20.5034 w/m2, Siberian Apricot needs the lowest value 16.8729 w/m2. Within one year, four plants'sap flows showed differences on the time of starting and peak, peak values and so on. ANOVA of average transpiration rates results showed that exotic specie Black Locust has no difference with Siberian native specie Apricot. Dateplum Persimmon transpiration rate is the lowest significantly, and evergreen tree Arborvitae is the highest. Four formulas tell the differences from exotic specie Black Locust to three other native species on how transpiration rate response to environment factors. Four formulas are showed below, SF Dateplum Persimmo=-0.3601+0.9840×Sr SF BlackLocust=1.6817-0.7432×At-1.1397×Ah+0.6216×Sr SF Siberian Apricot=-0.1582+0.9671×Sr SF Arborvitae=-0.4074+0.3358×At+0.6706×SrIn the equations:Sr is solar radiation, At is air temperature, Ah is air humidity, SF is sap flow. |
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