Vegetation Water Consumption And Soil Water Vegetation Carrying Capacity Of Hedysarum Leave And Salix Psammophila Plantations In Mu Us Desert Land

Moisture is the main factor limiting the growth and stability of vegetation in Mu Us Desert Land.Accurately obtaining the transpiration water consumption characteristics and soil water resources changes of typical afforestation tree species is the core problem to evaluate the stability of plantation community,guide the optimal regulation of stand structure and the rational allocation of vegetation.The study takes Hedysarum leave and Salix psammophila as the research objects,based on the characteristics of stand structure,conducts positioning and dynamic monitoring with thermal diffusion wrapped stem flow instrument,HOBO-U30 small meteorological station,Watch Dog2800 soil moisture automatic monitoring system and other equipment for positioning and dynamic monitoring,estimates the effective water storage of forest soil with precipitation infiltration process model(HYDRUS-1D),and reckons the bearing capacity of Hedysarum leave and Salix psammophila plantation relying on the principle of water balance.The main research results are as follows:1.Under the influence of rainfall time pattern,the soil moisture of Hedysarum leave,Salix psammophila and bare sand plots shows obvious seasonal and vertical changes.Soil moisture content is highest in August.The soil moisture profile of Salix psammophila plantation and bare sand sample shows an“S”type,and that of Hedysarum leave plantation shows an“3”type.Soil moisture content at 0-110cm depth:Salix psammophila plantation>Hedysarum leave plantation>bare sand.There are differences in soil water infiltration and depth between Hedysarum leave plantation and Salix psammophila plantation in the same rainfall event.The water supply of Hedysarum leave plantation during light rain event is greater than that of Salix psammophila plantation,and Water more easily infiltrates into deep soil layer of Salix psammophila plantation during rainfall events above moderate rain.The precipitation water greater than 8.8 mm can penetrate into the soil layer within 30 cm(the soil layer in which the roots of shrub and grass vegetation are mainly distributed in Mu Us sandy land),which is considered as an effective precipitation event.2.The result of simulating the comparative analysis of soil water infiltration rate of Hedysarum leave and Salix psammophila plantation through Kostiakov,Philip,Horton and general empirical formula indicates that Kostiakov model is suitable for describing the soil rainfall infiltration process of Hedysarum leave plantation,and the regression coefficients ranges from 0.9021 to 0.9518;The general empirical model is suitable for describing the rainfall infiltration process of Salix psammophila plantation,and the regression coefficient ranges from 0.7415 to 0.9923.HYDRUS-1D model with optimized parameters can accurately describe the soil moisture change process of Hedysarum leave plantation,Salix psammophila plantation and bare sand,and estimate the downward leakage and overall soil evaporation at 30 cm soil layer.During the peak season of vegetation growth from July to September,the infiltration flow of soil layer 30 cm or below in bare sand,Hedysarum leave and Salix psammophila plantation accounts for 78.08%,43.24%and 47.39%of the rainfall in the same period respectively.3.During the period of from July to September in 2017 and 2018,the average daily liquid flow rate of Hedysarum leave in Mu Us Desert Land is 15.18g/d and the average daily liquid flow is 364.42 g/d.The average daily sap flow rate of Salix psammophila branches is 17.01 g/D,and the average daily sap flow rate of Salix psammophila is 12245.73 g/d.The pant transpiration of Salix psammophila is significantly higher than that of Hedysarum leave.The liquid flow rate and flow rate of Hedysarum leave and Salix psammophila change with the change of meteorological factors,showing significant diurnal,diurnal and monthly process changes.Differences in response to environmental factors among the tested shrubs are that at the hourly and diurnal scales,the stem flow of Hedysarum leave and Salix psammophila is collectively affected by temperature,solar radiation,relative humidity and vapor pressure deficit;On the monthly scale,the stem flow of Hedysarum leave and Salix psammophila is affected by solar radiation.However,the difference is that the vapor pressure deficit is the main factor affecting Hedysarum leave,the temperature and solar radiation are the main factor affecting Salix psammophila.There are also differences in the response degree of the different diameter class to environmental factors.The response of small diameter plants to environmental factors is the lowest of Hedysarum leave.4.Based on water balance theory,the research estimates the recharge of soil water by HYDRUS-1D model,estimates the water consumption per plant(cluster)by vegetation water consumption model,and measures the vegetation carrying capacity of soil water in Hedysarum leave and Salix psammophila plantations which means that the suitable density of Hedysarum leave is 4701plants/hm~2,and that of Salix psammophila is about 1013clusters/hm~2.