| Land desertification is one of the serious global ecological environmental problems and the bottleneck of regional socio-economic development.Vegetation construction is an effective way to control desertification but the shortage of available water resources is a limiting factor for vegetation construction in desert areas.In order to improve the survival and conservation rate of vegetation in desert areas,and to solve the contradiction between vegetation growth and the shortage of available water resources,in this paper,the configuration of Nitraria roborowskii was studied after the artificial regulated by effects of plant endogenous hormones on changing the spatial morphology,increasing the plant root-crown ratio,promoting the water retention capacity from the above ground,and reducing the transpiration loss.Furthermore,the vegetation coverage in the sandy area and the ability of wind protection and sand fixation were improved.Besides,the application concentration,application frequency,and action time of the plant growth regulator by artificially regulating the ecological configuration and changing the spatial morphology of desert shrubs based on reducing water consumption were studied.The morphology,physiology and biochemistry,nutrients,roots,residues and degradation characteristics of Nitraria roborowskii were measured in order to cultivate the plants of short,strong,and root-developed and select the best application methods for improving the configuration.This not only provides a theoretical basis for reducing the amount of application and improving efficiency but also provides technical support for the targeted cultivation of resistant seedlings in arid and semi-arid areas.In order to explore the structural parameters of high-efficiency shrubs with wind-proof and sand-fixing and well understand the influence mechanism of shrubs on wind-sand movement,the effects of regulated shrubs with the different configurations on wind-resistant and sand-fixation in a wind tunnel experiment was further studied.It also provides a reference for the establishment of standard parameters for the ideal configuration of artificially regulating sandy shrubs.The results show that:The plant growth regulator not only reduced plant height,crown length,leaf length,leaf width,fresh weight and dry weight with above-ground,and it could promote the base diameter,crown width,leaf number,leaf thickness,root length,root average diameter,root surface area,root volume,root branch strength,root tip number,fresh weight and dry weight with roots.However,the high frequency(four times)would weaken the promotion effect.Besides,root diameter levels below 0.1mm responded most strongly to plant growth regulator.The variation of the crossover number was relatively flat compared to the cross number.According to the results of the comprehensive evaluation of plant growth indexes between different application frequency by a membership function and TOPSIS method,it was found that when the application frequency was one or two times,the higher concentration of 750mg/L should be used;when application frequency was three times,the concentration of 600mg/L should be selected;when application frequency was four times,the lower concentration of 300mg/L should be used.The plant growth regulator promoted the physiological and biochemical characteristics,but the high concentration weakened the promotion effect.All the experimental plots showed the changing trend of rising first and then decreasing(except for the evaporation rate in the experimental plot 1).When the application frequency was one time,the highest application concentration of the transpiration rate was 900mg/L,and the other physiological and biochemical indexes should not exceed 750mg/L.Besides,the photosynthetic characteristics in July and August were higher than those in September,and it reached the maximum in August.The comprehensive evaluation results showed that the higher concentration with 750mg/L should be used when the application frequency was one time;when the application frequency was between two and three times,600mg/L could be used;when the application frequency was four times,it is advisable to use a lower concentration with 450mg/L.In addition to the experimental plot 4,the plant growth regulator had a significant effect on total nitrogen,total phosphorus,and total potassium.The nutrient recovery efficiency of different application frequencies indicated that the plant growth regulator could promote nutrient recovery efficiency.However,the nutrient recovery efficiency would be negative with the increase of application concentration.High application frequency(four times)could reduce the nutrient recovery efficiency and the nutrient recovery efficiency of control was negative.In addition,the comprehensive evaluation results of the membership function method showed that when the application frequency was one or two times,600mg/L could be used;the higher concentration with 750mg/L should be used when the application frequency was three times;when the application frequency was four times,it is advisable to use a lower concentration with 450mg/L.The residual concentration was much higher than that in soil,and the application concentration was proportional to the residual concentration in soil and plants.The higher the application concentration was,the higher the residual concentration of plant growth regulators in soil and plants was.As the application frequency increased,the residual concentration in soil and plants gradually decreased.And the original attachment was proportional to the application concentration,which the higher the application concentration,the higher the original residual concentration(original attachment)of plant growth regulator.Moreover,the time in which residual concentration was completely degraded under the high application frequency and concentration would be delayed.The feasibility and safety of the above application method(high frequency and concentration of application)were proved.Regulated shrub with spindle-shaped had the best effect on wind speed weakening,and the greater the row space,the more stable the effect.However,the effects of regulated shrub with hemisphere-shaped and broom-shaped were almost the same.The effective weakening height of regulated shrub with different configurations was within 0.2cm-14cm.And the effective weakening distance was mainly in the front of first row 0.5H to the back of the last row-0.5H.Moreover,the decrease of wind speed in regulated shrubs with different configurations increased with the increase of wind speed.And wind speed and row space had little effect on the grain-size parameters.The grain-size percentage content under different height with sand collector was mainly concentrated in the medium sand in the range of grain-size from 500?m to 250?m,followed by fine sand in the range of 250?m to 100?m,and the clay content was the least.Furthermore,the sediment deposition of different configurations with regulated shrubs increased with the improvement of wind speed.The average sediment deposition of spindle-shaped regulated shrub in 17.5cm×17.5cm and broom-shaped regulated shrub in 17.5cm×26.25cm under wind speeds reached the highest.And there was less variation with the different configurations of regulated shrubs in 17.5cm×35cm under 12m/s and 16m/s.However,the sand resistance effect of broom-shaped regulated shrubs at 8m/s was the best.The sand resistance effect of broom-shaped regulated shrubs at 8m/s was better than that of spindle-shaped and hemisphere-shaped,while the sand resistance effect of different configurations with regulated shrubs in 17.5cm×35cm at 12m/s and 16m/s was the almost same. |
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