| Soil wettability refers to the process of replacing air with water on the soil surface.When the wettability of the soil is particularly poor,that is,water can not or it is difficult to moisten the surface of the soil,the performance of the soil water repellency.Soil water repellency can hinder surface water infiltration,increase the retention time of rainfall runoff and surface runoff,and aggravate soil erosion and soil erosion.It is for the temporal and spatial variation of soil moisture under vegetation.In this paper,soil under six local planting beds(Platycladus orientalis L.,Hippophae rhamnoides L.,Populus davidiana Dode.,Pinus tabulaeformis,Bothriochloa ischaemum L.,and Robinia pseudoacacia L.)in the loess hilly region of Ansai region was taken as the research object,and soil wettability was measured by WDPT method in four months in the field,to discuss the soil wettability strength and soil wettability changes with time under different vegetation.In this paper,WDPT of 100cm×100cm sample square soil was taken as the research basis,and its spatial variation was analyzed by using the semivariance function.At the same time,the soil wettability of different slope to slope position was studied.The wettability of soil aggregates with different diameters was studied.(1)Comprehensive six-planted soil WDPT,sorted according to different monthly WDPT,September(14.9s)> May(8.0s)> November(7.2s)> July(5.7s).The results of the four-month test of the soil under the Platycladus orientalis L.showed mild water repellency,and Robinia pseudoacacia L.soil was wettable after four months of testing.Based on four test months,the WDPT size of the six-planted surface soils was ranked as Platycladus orientalis L.(23s)>Hippophae rhamnoides L.(7.4s)>Bothriochloa ischaemum L.(7.2s)>Populus davidiana Dode.(6.8s)>Pinus tabulaeformis(5.9s)>Robinia pseudoacacia L.(3.4s).(2)It can be seen from the 100×100cm contour map that the water-repellent area of the soil in the surface layer of Platycladus orientalis L.is the largest,accounting for 67.7%,and the water-repellent areas of Hippophae rhamnoides L.,Bothriochloa ischaemum L.,Populus davidiana Dode.,Pinus tabulaeformis and Robinia pseudoacacia L.are reduced,respectively to 38.3%,37.4%,36%,33.9%,18.4%.The geostatistical analysis of a total of 120 100×100cm square WDPTs with six plants under four months showed that most of the best fitting models are exponential models,spherical model and Gaussian model followed,the maximum correlation distance varies from 10.1-311 cm.Comprehensive four months,the spatial dependence of the six plantings is ranked as Platycladus orientalis L.>Pinus tabulaeformis >Robinia pseudoacacia L.>Populus davidiana Dode.>Bothriochloa ischaemum L.>Hippophae rhamnoides L..The six plants were ranked by the strong spatial correlation ratio,Hippophae rhamnoides L.(94.4%)>Populus davidiana Dode.(89.5%)>Robinia pseudoacacia L.(86.7%)>Pinus tabulaeformis(85%)>Bothriochloa ischaemum L.(83.3%)>Platycladus orientalis L.(75 %).(3)Testing the wettability of different slope-oriented slopes with Hippophae rhamnoides L.as the dominant species.It is concluded that the WDPT value of the sunny slope soil is much smaller than the WDPT of the shade slope soil,that is,the wettability of the sunny slope is higher than that of the shade slope,and the sunny slope and the shade slope are from the uphill to the downhill,and the WDPT is gradually reduced.That is,the tendency of the wettability to increase.(4)The contact angles of soil aggregates with different diameters were determined,With the increase of the diameter,the contact angle of the 10 groups of soil samples varied from 64.76°~80.67° in the diameter of <0.2mm to 18.91° ~80.01° in the diameter 1.43 to 2 mm.It is recommended to test the contact angle with <1mm particle size soil in the laboratory.The contact angle of the agglomerates was found to be positively correlated with the organic carbon content.That is,wettability decreases as the organic carbon content increases. |
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