The Study On The Variation Of Temperature And Humidity Under Different Vegetation Cover In Shallow Loess

Because the temperature and humidity changes of shallow loess under different vegetation cover have an important impact on crop selection,plant growth,crop yield and fruit quality.In order to get the change rule of temperature and humidity of shallow loess under different vegetation coverage,the temperature and humidity of shallow loess under different vegetation coverage conditions were measured and tested by using Origin Software for function fitting and CFD method for numerical simulation,and the relevant change rule and model of temperature and humidity were obtained.The results show that:(1)In spring,5cm<15cm ? 30 cm,the temperature of 5cm soil layer is about 1.4 ? lower than that of 15 cm and 30cm;in summer,the temperature of 5cm,15 cm and 30 cm soil layer is about 22 ?;in autumn,the increment of interlayer temperature with depth is less than 2 ?;in winter,the increment of adjacent soil layer temperature is more than 2 ?.The maximum monthly soil temperature of A plots and C plots was in July,while that of B plots was in August.During April to October,the soil temperature in all plots was A>B>C,but the other time periods were opposite.The average annual temperature of loess is5cm<15cm<30cm;the order of temperature in the same soil layer is B>A>C.The order of soil daily temperature fluctuation is: 7:00<21:30<14:00.The variation amplitude of shallow loess decreases with the increase of depth,which can be expressed by index function:T = aebx,b<0 in April September,b>0 in other periods.(2)From spring to winter,the soil moisture of all kinds of land is 13%-24%,16%-25%,10%-22%,8%-20%,among which the order of soil moisture at 5cm is B<A<C,the order of soil moisture at 15 cm and30cm is A<B<C.The peak values of soil moisture in sample a and B appeared in July,while those in sample C were higher and less different in March,April,July,August and November.The change of soil moisture was gentle but the peak values were three,respectively in March,July and November.Although sample B was slightly higher than plot a,it was significantly lower than sample C.The annual average value of soil moisture of sample a and B is about 14%.The annual average value of soil moisture of sample C is more stable than that of sample a and B,which is more than 18% and about 4% higher than that of sample a and B.The difference between the maximum value and the minimum value of the three plots is a< B < C.The order of soil moisture in different depth of shallow loess is 5cm < 15 cm < 30 cm.The soil moisture in 5cm and 15 cm is a ? B < C.the soil moisture with covering measures at 30 cm is higher than that in bare land.(3)In the Gauss fitting of loess temperature,the offset(y₀)increases gradually with the increase of depth,the peak position(x_c)of different depths increases gradually with the increase of depth,and the width(w)and amplitude(A)of fitting curve of different depths of soil vary little.In the Gauss fitting of loess moisture,the deviation of moisture fitting function(y₀)of three soil layers of sample a is all above 11,and that of sample B is 15.3 at 5cm and 15 cm,and that of sample C is 15.9,14.8 and 20.7 at 5cm,15 cm and 30 cm,The order of humidity is A<B<C.In the temperature nephogram,the soil temperature changes about 6 ? from the surface to the depth of 45 cm,and the soil temperature rises gradually,which is basically consistent with the measured situation.On the moisture cloud chart,the soil surface moisture is the lowest,only 6.7%,and the soil moisture value at 45 cm is 10.2%.The soil moisture increases with the depth,and the simulation results are consistent with the measured results.