| Jartai Salt Lake is located in the southeast of Alxa Plateau with drought and sandstorm.Appropriate afforestation is one of the important measures to control sand damage and improve ecological enbironment in this area.In this paper,the sample plots of three afforestation methods(planting in good water condition,water jetting,and planting in mechanical hole afforestation)in the Jartai Salt Lake area were used as the sampling points for the test materials.The growth characteristics of Haloxylon ammodendron in this area were investigated and studied by using the methods of field investigation and sampling and laboratory tests.The characteristics of Haloxylon ammodendron(e.g.plant height,crown,base diameter,branching architecture and biomass allocation in overground,water and physiological characteristics)in assimilated branch in different afforestation methods were analyzed.The test results can provide a theoretical basis for selecting reasonable and effective afforestation methods in Jartai Salt Lake Area.The results showed that:(1)There were differences in plant height,crown,base diameter and growth rate of Haloxylon ammodendron in different afforestation methods.Haloxylon ammodendron was belong to the mode of increased growth in the water jitting,while it was belong to the cross growth mode in the planting in good water condition.The individuals of planting in mechanical hole afforestation has relatively poor horizontal and vertical growth.(2)The basic characteristics of branch components branch length,branch diameter,branch angle,branch volume of Haloxylon ammodendron were best in the planting in good water condition,the second was the water jitting,the planting in mechanical hole was the smallest.In the planting in good water condition method,the branch length and branch angle of ? branch were 7.61±0.70 cm,47.64±2.28° and the diameter of the ?,? branches were 1.89±0.11 mm?1.27±0.05 mm,respectively.In terms of bifurcation ratio and branch fractal characteristics showed more strong advantages in wate jitting.Under this mode,the overall bifurcation ratio is 6.51±1.95%,and the correlation coeffcients of the fitting equations of crown fractal dimensions(2.05)and box counting dimension(0.49)were all 0.89.(3)Under the three afforestation methods in the study area,the water content of assimilated branches of Haloxylon ammodendron in planting in mechanical hole was more better,the higher content of water in the plant greatly increased the survival probability of the plant in arid environment.Under this mode,the water content and carnification of assimilated branches were 63±0.01%?1.30±0.04%,respectively,and the water retention ability was 50.01 h;the bound water content and bound water/free water performance of assimilated branches were also the highest.The photosynthetic physiological characteristics of the water jitting was the best,because there were more annual branches and complicated and reasonable spatial distribution of branches under this method.The contents of chlorophyll a,chlorophyll b and total chlorophyll were the highest in the water jitting,so plants had the best absorption efficiency of light energy and nutrients.(4)The biomass distribution characteristics was that the biomass was larger in the water jitting.Because plants had more branch biomass in the water jitting,their assimilates branch biomass,nutrient component biomass and total biomass were the latgest,which were 1396.98±920.66 g,1857.02±1054.51 g,1865.68±1055.97 g.The flower-assimilated branch,the stem-assimilated branch,the nutrient component-reproductive compont all showed extremely significant allometric growth relationship(P<0.01).(5)Through the rincipal component analysis,the comprehensive score was the water jitting>the planting in good water condition>the planting in mechanical hole afforestation. |
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