The Eco-physiological Response Mechanisms And Strategies Of Haloxylon Ammodendron Under The Influence Of Water And Salt

The carbon-water balance in trees is broken by many interferences and thus it is difficult to maintain the growth and the phenomenon of widespread forest decline and plant death have become hot topics.Water plays an important role in the relatively weak arid desert region,and is the main driving factor and limiting factor of the area's occurrence and succession.The desert ecosystem is distributed in Ebinur Lake Basin in arid area.Vigorous evaporation and salt moved with water which form the distribution pattern of water and salt in the soil with high salt to high water,and little salt to little water.Therefore,salinization controls the degree of combination variation between factors as well as drought.The difficulties of coercion plants are faced with can be adjusted by physiology in the short term and regulated by morphology in the long term.Previous studies on plant carbon water physiological responses mostly focused on drought,insect pests,shading and other stresses,only few studies centered on the effects of double stress of carbon-water balance in forest in situ.In addition,the plant watercarbon physiological response to the external environment is closely related to the body elements.Woody plants are group species and dominant species of desert ecosystem,studying its carbon-water physiological response to external stress,morphological adjustment mechanism on the ground and exploring the relationship between former physiological changes and the nutrient element are important to explain the physiological response mechanism and ecological adaptation of plants in desert ecosystem.Belongs to super xerophytic and strong resistance to salt sand fixing plants in arid areas,Haloxylon ammodendron is of great significance for the stability and conservation of desert ecosystem in arid area.Understanding the carbon-water dynamic response and morphological adjustment mechanism of Haloxylon ammodendron is helpful to comprehend and predict changes in its population and the relationship among Haloxylon ammodendron communities.Otherwise,the element utilization strategy and non-structural carbon shape and dynamic adjustment of Haloxylon ammodendron relates closely,so it is worth further discussing about its effect of the measurement relationship between the element absorption strategy and the carbon dynamics on survival.Based on the soil water and salt gradients,the study observed carbon-water physiological and morphological indexes and chemical measurement characteristics of carbon,nitrogen and phosphorus of Haloxylon ammodendron to determine its carbonwater physiological response mechanism and morphological adjustment strategy;meanwhile,obtained intrinsic relationship between the absorption of elements and the physiological function.The results showed that:(1)In high water and high salinity environment,serious soil salinization led to the difficulty of root water absorption.The Haloxylon ammodendron tree adopted the strategy of reducing the water potential of assimilating branches at night and lower than the water potential of the two grade branches to absorb and utilize the canopy dew and maintain the balance of water,and the strong stomatal regulation ability and the efficient water use efficiency,so that it can improve the net photosynthetic rate in the daytime;The control ability of the stomatal behavior of Haloxylon ammodendron trees decreased slightly under the middle water and salt environment,and the high transpiration rate made the xylem have a developed water guide system to keep the water demand in the body,but this would increase the consumption of water and the respiration rate at night,and need to consume more carbohydrates to maintain the safety of the transport system;However,Haloxylon ammodendron not only had no reverse water potential gradient,but also no efficient water conductivity,though higher stomatal conductance can be maintained to improve photosynthetic rate,interestingly.(2)With the decrease of soil moisture and salt content,the height,basal diameter,crown area and specific leaf area and total nonstructural carbohydrate content of Haloxylon ammodendron was significantly decreased This morphological adjustment in the upper part of the earth is similar to "self-thinning",which aimed is to reduce the transpiration area and balance the carbon distribution in the plants.Plant carbon accumulation could resistance the double of drought and salinization.Haloxylon ammodendron showing high total nonstructural carbohydrate content,plant height and width shape under the soil environment with high water and salinity;However,Haloxylon ammodendron showing low total nonstructural carbohydrate content and plant morphology thin and small under the soil environment with low water and salinity;The total nonstructural carbon content of Haloxylon ammodendron and tree morphology were between the above two soil enviroment in middle water and salinity.(3)The content of carbon,nitrogen and phosphorus of Haloxylon ammodendron in the Ebinur Lake Basin were lower than other vegetation of terrestrial ecosystem;With the decrease of soil moisture and salinity,the carbon content of the assimilating branches tended to increase,and the carbon content of the secondary branches decreased first and then increased,while the nitrogen and phosphorus content of both tissues decreased gradually and the nitrogen and phosphorus are negatively correlated with carbon elements at the same time.Nitrogen/phosphorus of the assimilating branches was generally greater than 16,which mainly limited by phosphorus.There was a significant negative correlation between total non-structural carbon and carbon content,but significant positive correlation with the content of nitrogen and phosphorus of Haloxylon ammodendron.And there is a strong positive correlation between the total non-structural carbon/phosphorus and nitrogen: phosphorus,while the total nonstructural carbon: nitrogen and nitrogen: phosphorus is not significant.The above results showed that the total non-structural carbon of synthesis and accumulation in Haloxylon ammodendron by the influence of carbon,nitrogen and phosphorus content and the root may be to an upper part of conveying the content of phosphorus in the size of a qualitative will important for regulating nutrient element balance and non-structural carbon dynamics.