| In ramosissima Bosten lake shore with the natural growth of the north shore of the research material, along the shore in the direction approximately perpendicular to the lakeshore and water and salt from the water distribution and the selection of four different plots. And in four plots, Tamarix vegetation select growing well established 5m*5m plant plots, within plots ramosissima the number of trees, crown, physiological characteristics height, diameter and other classified and recorded in the sample subregion where the natural stratification divided by 0-10 cm, 10-30 cm, 30-60 cm,60-80 cm,80-100 cm, a total of five soil digging soil profiles and soil samples, measurements in the laboratory Analysis of soil moisture and salinity characteristics. Using LI-6400 photosynthesis system of ramosissima four samples within the diurnal variation of photosynthetic characteristics under typical weather for analysis. O n this basis, the use of the methods and principles of statistics, explore different water and salt gradient ramosissima different characteristics of photosynthesis variety characteristics and laws of time and space. At the same time revealing response relationship between the various plots ramosissima diurnal variation of photosynthetic characteristics and water- salt gradient change. To protect Bosten Lake area of wetland vegetation, and provide a reference for understanding the growth of tamarisk in photosynthetic vegetation under different water and salt gradientResearch results show that:(1) to the characters of different distances away from the lake lake shore four sample soil salt distribution rules of analysis, the results show that in addition to the sample area four salt content is low, other kinds of soil salinization is clearly more severe and table together. Due to the strong evaporation activities, amplitude of ground surface soil salt content, the biggest change range of 0.127% to 0.127%, at the same time also showed a strong spatial correlation. All kinds of ground surface soil salt content is highest, with the loss of the depth, after a declining trend. The layers of soil salt ion of anion in C l- and SO42- the largest percentage, 0.655% and 1.642% respectively, proportion of cation with Na+, K+ 1.224% maximum. O f four sample plots of soil salt ion is roughly same, has a bigger difference in vertical direction.(2) the different distances from the lakes of four sample plots of tamarisk photosynthetic characteristics were analyzed, and the results showed that four sample plots in different age paragraph the tamarisk net photosynthetic rate of change is big, show unimodal curve, and the difference to be markedly, according to the size of the order: foth sample > thrid sample > second sample > frist sample. Variation characteristics of stomatal conductance and net photosynthetic rate, the size of the show with the increase of moisture and salt, net photosynthetic rate and stomatal conductance are affected, four kind of tamarisk water use efficiency, all show the morning water use efficiency was significantly higher in the afternoon. Through correlation analysis and regression analysis showed that all kinds of tamarisk net photosynthetic rate and effective radiation was significantly positively related to the sun, but the other environmental and physiological factors, such as air temperature, air relative humidity, water use efficiency(wue) and intercellular CO2 concentration in different extent impact on it.(3) four sample area change curve of soil water content, are characterized by rising curve. C losest to the lake water sample to the soil moisture content is among the highest in the four sample, at 30.643%, due to all kinds of soil water content with depth of down and up, with the increase of soil depth, soil water content, time and space distribution of soil salt have significant profile distribution pattern.(4) the tamarisk photosynthetic rate between the influence factor and the soil salinity gradient changes of correlation analysis showed that the water and salt under the condition of different kinds to tamarisk photosynthetic characteristics affected by water and salt are different. In a soil sample to 10 cm, salt and intercellular CO2 concentration, atmospheric CO2 concentration(Ca) present positive correlation, the correlation coefficient of 0.411 and 0.405. With the air relative humidity has significant negative correlation.Because of the difference of all kinds of land as the distance from the lake, soil moisture content is reduced gradually, and the soil moisture content and net photosynthetic rate, transpiration rate rises with the decrease of water content, the relevance of the positively correlated relationship and correlation are close. Negative correlation with the intercellular CO2 concentration, the correlation of soil moisture content and other factors.(5) in addition to the 0 to 30 cm layer of total nitrogen, Na+, K- ion, total salt, total nitrogen ions and total salt has suppression characteristics to the tamarisk plant height, other ions in each layer of tamarisk plant height in order to promote role. Tamarisk crown length and width in different soil layer under the influence of soil salt ion is roughly same, 10 cm, 60 cm, 100 cm of HCO3- ion and total nitrogen ions, of tamarisk can inhibit the crown length and width, 60 cm soil total salt on the crown length and width of negative correlation, while other layers are positive correlation.Soil moisture content on the variation of plant height of tamarisk has more obvious influence and role. Tamarisk crown length and crown width and density growth with the increase of the depth of soil layer, the correlation, the positive correlation coefficient of the change, showed that soil moisture on the crown length and crown width and the density of tamarisk has more significant effect.Research shows that: when the plants under a state of the lack of soil moisture for a long time, will the physiological status of tamarix obvious effect, and high soil salt can make the photosynthesis of tamarix is restrained, the lack of water is indirect influence the decline of photosynthesis tamarisk belong to salt, drought resistance of plant species, the moderate salt drought environment will allow them to quickly adapt to the environment change, for better growth and competitive advantage of ecological adaptability is stronger. But the same properties of plants in different habitats by restricting factors is different, so its growth characteristics also vary. |
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