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Water Source And Utilization Efficiency Of Typical Tree And Shrubs In The Water-wind Erosion Crisscross Region

Posted on:2019-11-21Degree:MasterType:Thesis
Country:ChinaCandidate:T WeiFull Text:PDF
GTID:2370330569487284Subject:Soil science
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Water is the most important limiting factors for ecological processes and functions in arid and smei-arid ecosystem,and plays an important role in plant growth and distribution.As typical tree and shrub plantations,Populus simonii,Caragana korshinskii and Artemisia desertorum have important theoretical and practical effects on the protection of species diversity in arid and smei-arid areas.Therefore,studying the water use strategies of these three plants are necessary for ecological restoration and construction.In this study,we selected P.simonii,C.korshinskii and A.desertorum located in the Liudaogou watershed as the research target.The photosynthetic characteristics,water potential and?13C of P.simonii were analyzed under different canopy heights;Characteristics of water source changes of A desertorum were analyzed under drought control conditions;Water use strategies of C.korshinskii and A.desertorum were analyzed in different months.The main results were as followings:?1?Photosynthetic parameters Pn,Gs,Ci and Tr of P.simonii decreased along with the increaseing of canopy height.The values of?13C increased with the increasing canopy height,and the correlation between?13C and photosynthetic parameters is also enhanced.The water use efficiency of the upper canopy was higher than that of the below canopy.The leaf water potential had a decreasing trend with the changes of the canopy height,and became stronger due to the limitation of water stress with the increasing canopy height.These findings supported the hypothesis of hydraulic limitation.?2?Under natural conditions,soil water content and stable isotope composition in the surface layer?010 cm?fluctuated greatly and surface soil water content ranged from 0.97%to 4.48%.While under drought control conditions,both soil water content and stable isotope composition were relatively stable and surface soil moisture content ranged from 1.23%to1.47%,which indicating that the surface soil under natural conditions is greatly affected by both soil evaporation and rainfall;?D and?18O values in soil water deviated significantly from the local meteoric water line,and soil water experienced evaporation and fractionation,while the slope of soil evaporation line under two water conditions was different,indicating that the degree of evaporation and fractionation experienced by soil water under drought conditions was greater than that of natural conditions.?3?Under natural conditions,A.desertorum mainly used 60 to 100 cm of soil water on August 7th when rainfall was small,while soil water within 0 to 30 cm was supplemented by more small rainfall events on September 27th,and it began to use soil water within 30 cm.Under drought conditions,the root uptake depths of A.desertorum changed with soil water conditions,and its mainly used 80100 cm soil water when the drought control was 36 d.This indicated that the root of A.desertorum had a positively respond to water deficit and this response would be beneficial to its adaptation to water stress.?4?The water sources of C.korshinskii and A.desertorum differed in different months.In May,C.korshinskii mainly used soil water of 60100 cm,while for A.desertorum,corresponding depths was 1030 cm.For either C.korshinskii or A.desertorum,the proportion of water use had little difference among different layers;In June,rainfall was greater than in May,and soil water within 060 cm that supplemented by rainfall also increased significantly,C.korshinskii increased the proportion of soil water within 060 cm,A.desertorum was sensitive to soil water,so the proportion of soil water resources within 30cm increased rapidly;The main water sources used by C.korshinskii and A.desertorum from July to September were similar,and both used soil water of 3060 cm,010 cm,and 010cm,respectively,the utilization of these water sources were 68.4%,49.1%,75.3%and66.1%,43.3%and 95.0%.?5?Photosynthetic physiological indicators of C.korshinskii and A.desertorum showed similar changes during the observation period,and were relatively low in May and June with less rainfall,and at a higher level in August with more rainfall.The photosynthetic physiological indicators decreased at the late growth stage in September.C.korshinskii had the characteristics of low photosynthetic rate,low transpiration rate,and high instantaneous water use efficiency,indicating that it have a drought tolerance water use strategy.A.desertorum had the characteristics of high photosynthetic rate,high transpiration rate,low water use efficiency and high leaf water content,indicating that it had a drought avoidance water use strategy.The instantaneous water use efficiency of C.korshinskii in different months was more stable than that of A.desertorum,indicating that A.desertorum is more sensitive to the drought response.The?13C values of leaves of C.korshinskii fluctuated between-28.55-26.09‰the mean value was-27.25‰,and the?13C value of A.desertorum leaves fluctuated between-29.31-8.09‰,with an average of-28.74‰.The?13C values of it in May and June with less rainfall were larger,but the?13C values became smaller with the increaseing of rainfall.The?13C values of C.korshinskii in each month were greater than that of A desertorum leaves,it showed that the long-term water use efficiency of C.korshinskii was higher than that of A.desertorum.
Keywords/Search Tags:photosynthesis, water resource, water use efficiency, ?13C value, stable hydrogen and oxygen isotope
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