Soil Preferential Flow Characteristics Of Pinus Sylvestris Var. Mongolica Plantations At Different Forest Ages

In northwest Liaoning Province,there is little rainfall,large evapotranspiration,strong wind-sand activity,and preferential flow is easily produced under the action of soil animals and plant roots.Therefore,the study of preferential flow in wind-sand land in Northwest Liaoning Province is of great significance for further understanding the process of soil infiltration and recharge,vegetation restoration,soil and water conservation,and prevention and control of groundwater pollution in wind-sand land in Northwest Liaoning Province.In order to clarify the characteristics and influencing factors of soil preferential flow in sandy land of Northwest Liaoning Province,this paper takes Pinus sylvestris var.mongolica forest land of different forest ages in sandy land of Northwest Liaoning Province as the research object,and carries out outdoor soil preferential path dyeing experiment;indoor soil macropore,soil physical and chemical properties determination experiment,combined with soil physical and chemical properties,soil water penetration curve,root index,dyeing profile image,etc.The results show that:(1)Soil natural water content,total soil porosity,capillary porosity and organic matter decreased with the increase of soil depth in the four plots,but soil bulk density was contrary to its trend.Soil natural water content and organic matter increased with the increase of forest age,while bulk density and total porosity decreased.(2)The water penetration curves of the four plots showed an increasing trend,and the outflow rate tended to be sTable at 80-90 s and sTable at about 100 s.The steady outflow rate of 24 and 49-year-old Pinus sylvestris var.mongolica forest land and control plot decreased with the increase of soil depth.The number of soil macropore decreased with the increase of soil layers in the four plots.The radius of soil macropore ranged from 0.69 to 3.66 mm may affect water transport.(3)There are obvious preferential flow in the four sample plots.The depth range of uniform dyed area of the four sample plots is 0-8 cm,0-10 cm,0-15 cm and 0-20 cm respectively.The maximum dyed depth of the four sample plots is also different.Compared with the control plots > 49 years > 38 years > 24 years,the ratio of dyed area of the four sample plots decreases with the increase of soil layer.By analyzing the characteristics of preferential flow in four plots,it is found that the characteristics of preferential flow in 49-year Pinus sylvestris forest land are similar to those in the control plot.With the increase of forest age,the root system of Pinus sylvestris forest develops,which results in the increase of macropore depth and the decrease ofsoil water-holding capacity,which has a negative effect on the control of aeolian sandy soil.(4)The root length density of the four plots decreased with the increase of soil depth.The root length density of 0-10 cm soil layer was the highest,and the value of root length density of dyed zone was 49 years > control > 38 years > 24 years.With the increase of forest age,the root length and density of Pinus sylvestris var.mongolica forest also increased,and the ratio of dyed area also showed an increasing trend.Root biomass of the four plots increased obviously with the increase of forest age.Root biomass had some influence on preferential flow path,but this effect was not significant.