Study On Soil Properties Variation Of Different Land Use Types In Southern Horqin

The process of desertification controlis accompanied by the change of land use type.Land use type not only visually changesthe surface morphology and coverage,but also affectsphysical and chemical properties,structure and function ofsoil.Reasonable land use plays an important role in promoting the reconstruction and restoration of regional vegetation and increasing ecosystem stability.We chose Pinus sylvestris var.mongolica Litv plantation,Populus simonii Carr plantation,Caragana microphylla Lam plantation,Salix gordejevii Y.L.Chang&Skvortsov community,corn field,orchard,fruit-grass mixtus land,fencing land,moderate grazing land,fixed sandy land,semi-fixed sandy land,low-land as research objects,shifting sandy land as a control sample,analyzed the soil restoration effect of different land use types by combining the method of space time substitution with paired sites.BP neural network was used to construct the soil water characteristic curve transfer function of 0-60cm profile,and the soil water holding capacity under different land use types was defined.Based on the annual average precipitation and plant water consumption,the paper analyzed the water consumption relationship between plant and soil.The conclusion is not only an important basis to determine the rationality of current land use in Horqin sandy land,but also can provide reasonable suggestions for the future land desertification control.The main results of this study are as follows:The physical and chemical properties of soil can be obviously improved by artificial afforestation,enclosure and agricultural utilization.The cluster analysis of soil physical and chemical properties was carried out.In the method of cluster analysis,these indices were joined by Ward-method,the distance between two indices was measured by squared euclidean distance,set 80 percent as a similarity level.The result shows that thirteen kinds of land use types were divided into four groups.Take shifting sandy land as control,the best effect on soil physicochemical properties recovery of eight rain-fed land use types is Populus simonii Carr plantation after the exclusion of agricultural land.The similarity degree among Pinus sylvestris var.mongolica Litv plantation,Populus simonii Carr plantation,fencing land was 80.94 percent.The V-G model simulation results of soil saturated and residual water rate show high accuracy,and it is higher for residual water rate.The soil moisture PTFs was constructed based on BP neural network,the resulting water characteristic curve is in agreement with the measured value.The correlation coefficient R~2 between simulated values and measured values of four soil water parameters is above 0.98.The model can accurately predict the whole 0-60cm soil profile.Soil water holding storage ability was higher in corn and orchard during 13 land use types,soil effective water content was higher as well,but the soil water potential and soil water content ratio is bigger,it means easier to form the drought when soil volume water content reached 20%.The proportion of soil excess water was larger in the other land use types,and it is less prone to drought.To ensure the plants growth normally,the theoretical value of annual irrigation water of corn and orchards is about 504~567mm precipitation,and the actual irrigation irrigation amount is far greater than the theoretical value,serious consumption of groundwater;The water supply is greater than demand in Populus simonii Carr plantation,Caragana microphylla Lam plantation and mixture.The other land use types can maintain normal growth under the condition of rainfall,and also have a supplementary effect on groundwater.By the systematic analysis of soil physical and chemical properties recovery effect and water dependency of 13 land use types,the result showed that the fencing can recover soil physical and chemical properties good,conserve water,and the pressure on soil water vegetation carrying capacity is less,thus fengcing is the most suitable for local ecological restoration under rain-fed conditions.In the current irrigation mode,corn and orchards had a huge water consumption.It will hinder the ecological restoration in Horqin Sandy Land,these two land use types should be improvement or limitation.