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Photosynthetic, Water Consumption Characteristics Of Salix Gordejevii And Caragana Microphylla In The Dune-meadow Ecosystem Of Horqin Sandy Land

Posted on:2017-01-05Degree:MasterType:Thesis
Country:ChinaCandidate:Y LvFull Text:PDF
GTID:2180330488975236Subject:Hydrology and water resources
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Photosynthesis and transpiration are the main physiological processes of plant life activity. Especially in the lack of rain, the wind sand much and strong solar radiation under the special environment. Natural vegetation occupies the important status in the area of afforestation. So study the photosynthetic and transpiration characteristics of natural vegetation in the region has great significance. In this paper, plants’ photosynthetic and transpiration was measured using the Li-6400 photosynthetic apparatus and Stem-Flow gauges.Major conclusions are as following:(1) The curves of net photosynthetic rate and stomatal conductance of Salix gordejevii and Caragana microphylla take shapes of single-peaks or multi-peak type, while the daily variation of intercellular CO2 concentration show the opposite to the net photosynthetic rate trend. The order of average value of the net photosynthetic rate and stomatal conductance of two kinds of shrubs is:Pn (Salix gordejevii)> Pn (Caragana microphylla), Cond (Salix gordejevii)< Cond (Caragana microphylla).(2) The net photosynthetic rate of Salix gordejevii has significant positive correlation with transpiration rate, solar radiation and stomatal conductance, and negatively related with intercellular CO2. The net photosynthetic rate of Caragana microphylla has significant positive correlation with transpiration rate, solar radiation, stomatal limitation and water use efficiency, and negatively related with intercellular CO2.(3) Modified rectangular hyperbola model can better fitting this two plants photosynthetic rate with the actual circumstances of the light intensity and CO2 concentration change. It suggested that Caragana microphylla had stronger ability to adapt to the ebvironment. Habitat of high CO2 concentration can promote the growth of Salix gordejevii. Caragana microphylla showed a strong ability of CO2 assililation.(4) The transpiration rate of two plants take shapes of single-peaks or multi-peak type, and the multi-peak type accounted for the vast majority of transpiration process. The transpiration rate of two kinds of shrubs has significant positive correlation with air temperature and light intensity and negatively correlated with air relative humidity. The transpiration rate of Salix gordejevii has significant positive correlation with 80cm soil water content, and has no significant correlation with soil temperature. The transpiration rate of Caragana microphylla has significant positive correlation with 10cm,20cm, 40cm,80cm,120cm soil water content, and has significantly negative correlation with soil temperature of different depth.(5) Diurnal change of sap flow velocity showed minor fluctuations during three kinds of different weather conditions, and displayed a more peak type. Under sunny conditions, the sap flow peak of Salix gordejevii can sustain 7.5h. The sap flow peak of Caragana microphylla can sustain 10h. Under cloudy conditions, the sap flow peak of Salix gordejevii can sustain 3.5h. The sap flow peak of Caragana microphylla can sustain 8.5h. Under rainy conditions, the sap flow peak of Salix gordejevii can sustain 2h. The sap flow peak of Caragana microphylla can sustain 4h. Under different weather conditions, the main meteorological factors affecting the stem flow rate is solar radiation.(6) Small rain events (<10mm) did not change the sap flow, whereas moderate rain(10-20mm) had changed a little and large rain events (>30 mm) significantly increased the sap flow on days following rainfall.(7) Using the cross-section of stem and leaf area for extending scalar. Then calculated the transpiration of Salix gordejevii and Caragana microphylla in the growing season. The total water consumption of Salix gordejevii and Caragana microphylla are: 314.7 mm and 106.3 mm. Using the Penman Monteith equation to calculate forest transpiration of Salix gordejevii and Caragana microphylla and compared two methods showed that the results are in good agreement.
Keywords/Search Tags:Salix gordejevii, Caragana microphylla, Photosynthetic characteristics, Transpiration, Scale extension, Penman-Monteith
PDF Full Text Request
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