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Northwest A&F University (2017)

Effects of Land Use on Soil Hydraulic Properties in the Loess Plateau,China

Kalhoro Shahmir Ali

Titre : Effects of Land Use on Soil Hydraulic Properties in the Loess Plateau,China

Auteur : Kalhoro Shahmir Ali

Grade : Doctoral Dissertation 2017

Université : Northwest A&F University

In order to evaluate the soil hydraulic parameters affected by the land use types in the Loess Plateau regions,the present study was carried out in 2015-2016.The loess soil area is very fragile in nature and in 1999 Chinese Government launched the special project titled as“Grain for Green”for the enhancement of soil dominance and a decrease of soil erosion in the Loess Plateau.On the other side due to extensive vegetation restoration on the Loess Plateau,The area(mainly the present study area)also facing some issue such as soil desiccation and river flow decrease which threaten the regional water recycling and drinking water safety.The research on macropores from root system is helpful to study the mechanism of groundwater recharge and improve the infiltration models of an inhomogeneous medium.Cropland,forestland,and grassland in different utilization years are the objects of this.The root characteristics of the soil core method and the root image scanning of the root analysis provide the relation between root development and the formation of macropores in the process of vegetation restoration.Additionally,indoor experiments of soil water characteristic curve also provide the base the link between pores characteristics.The results could be used to evaluate the influence on the soil recharge ability to groundwater,and it can help deeply understood of the regional hydrological response caused by Land Use and Land Cover Change and provide a national ecological construction with some reliable basis.Grassland has high value in soil organic matter 17.96±0.89 g kg-1 at top soil layer,and the minimum was recorded in cropland maize 10.72±0.03 g kg-1at sub-soil layer.The higher electrical conductivity was noted in common apple orchard followed by abandoned apple orchard,grassland,cropland wheat,cropland maize and shrub-grassland respectively.Conclusively,the results of soil basic properties demonstrate that grassland and shrub-grassland uses are the most efficient and suitable land use system to improve soil organic matter conservation compared to other land use.In order to protect soil quality and health to maintain the sustainable agricultural development,the conversion of farmland to grassland or other alternate suitable land use should be an ideal practice for soil organic matter and associated soil properties.Soil aggregate stability is akey indicator for controlling soil losses and to improve soil quality.Higher percentages of water stable aggregates were observed in the shrub grassland and grassland at 0-20 cm of soil layer 65%and 61%,respectively.Moreover,in comparison of croplands,cropland wheat has more percentage of dry stable aggregate and water stable aggregate 56%and 42%as compared to cropland maize 50 and 49%respectively.Whereas the abandoned apple orchard has 73%and 50%and common apple orchard have 55%and50%.Both mean weight diameters and geometric mean diameters of aggregate were recorded higher in grassland than the other land uses ;the results are highly significant under different land use .The formation of soil aggregates and their stability were positively correlated with soil organic carbon content and root biomass of different plant communities.Furthermore the correlation coefficient of mean weight diameter,geometric diameter,root biomass,and soil organic carbon content were also highly significant.Increased soil organic carbon concentrations were closely linked with the formation of macro-aggregates.

Mots clés : Soil Aggregates; Soil Infiltration Rate; Soil Organic Carbon; Soil Water Characteristic Curve; Root Ct-Scanning; Land-use; Loess Plateau;

Présentation (CNKI)

Page publiée le 28 mai 2018