Study On Characteristics Of Sap Flow Of Salix Psammophila And Soil Structure In Mu Us Sandy Land

In the Soil-Plant-Atmosphere continuum,soil and plant transpiration play very important roles,especially in areas with severe desertification and soil erosion.In order to fully understand the characteristics of sandy soil structure and the transpiration regularity of dominant shrub species in sandy land and their response to environmental factors,this experiment was carried out in Mu Us sandy land of Wushen Banner,Ordos.The Salix psammophila and the soil at different depths near the clump were used as the research object.Three groups of Salix psammophila are set up,and the annual(1a)Salix psammophila is 4?8 mm in diameter;the 2 years(2a)Salix psammophila is 8-12 mm in diameter;The diameter of 3 years Salix psammophila(3?5a)is more than 12 mm;and 3 slope positions are set(flat beach(P1),middle(P2)and top(P3))and 3 time scales(month scale,day scale and hour scale).The wrapped sap flow meter based on the principle of heat balance is used to monitor the long-term continuity of Salix psammophila and to continuously and continuously observe the surrounding environmental factors,including meteorological factors(photosynthetically active radiation PAR,air temperature T,air humidity RH,and water pressure difference VPD,Wind speed Vw,etc.)and soil factors(soil temperature ST,soil water content SW,etc.);ring knife profile soil extraction and drying method to measure soil water capacity and calibrate soil water content;Gemini ? 2390 specific surface area analyzer perform pore structure feature analysis.By analyzing the characteristics of Salix psammophila sap flow on a spatial and temporal scale and soil pore structure,the plant transpiration and soil characteristics in arid and semi-arid regions are explored in order to provide basic data and theory for the management of Salix psammophila plantations in the Mu Us sandy land.The results of this test are as follows:(1)The sap flow of Salix psammophila at different slope positions is the same,showing a multi-peak "?" shape curve.All three had transpiration midday breaks,and there was a slight transpiration phenomenon at night;There were topographic differences in the flow accumulation,and the overall trend is P1>P2>P3.Among them,PI is significantly different from P2 and P3,and P2 and P3 are not significantly different.At the same slope position,the sap flow of Salix psammophila showed a trend of 3-5a>2a>1a.The sap flow of Salix psammophila at three slope positions was significantly related to meteorological factors,including a significant positive correlation with PAR,T,and VPD,and a significant negative correlation with RH.In the multiple linear stepwise regression model,different slope positions and different diameter ranges the selected meteorological factors are slightly different,but PAR and T dominate.(2)The effects of environmental factors on the sap flow of Salix psammophila have significant differences on the time scale.On the monthly scale,the sap flow of Salix psammophila was mainly dominated by soil factors.Soil factors can be used according to the regression model(R2=0.93)to estimate Salix psammophila's sap flow;on the daily and hour scales,the sap flow was affected by more environmental factors,the meteorological factor was dominant,and the regression model R2 was small,which should be monitored directly by an instrument;under sunny conditions,the sap flow correlation between the rate and each meteorological factor was better than that of rainy weather.In the model of the relationship between the sap flow rate of Salix psammophila and the meteorological factors,the influence factors of meteorology on the sap flow rate of Salix psammophila are different.Through scale expansion,it is found that the transpiration of Salix psammophila is much larger than the rainfall,and the supply and demand were unbalanced.Salix psammophila can be stubbed regularly to reduce transpiration consumption.(3)For three different slope positions,the soil moisture content at P1 was higher,and Salix psammophila grows best,followed by P2.The Salix psammophila willow pruning rate was higher at P3,and the retention rate was lower,but the top effect was significant.P1 is more suitable Salix psammophila growth;BET isothermal adsorption model was more suitable for analyzing sandy soil than other models.The isothermal adsorption curves of soils at different slope positions and different depths were slightly different.The proportion of mesopores in soil pores at the 3 slope positions was the largest.Macro holes were next,and micro holes were the smallest.