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Northwest A&F University (2022)

Modeling Soil Water Dynamics in Response to Landuse Change in China’s Loess Plateau

白晓

Titre : Modeling Soil Water Dynamics in Response to Landuse Change in China’s Loess Plateau

Auteur : 白晓

Grade : Doctoral Dissertation 2022

Université : Northwest A&F University

Résumé partiel
The introduction of high water-consuming plants and high-density planting in the Loess Plateau resulted in deep(>1 m)soil water deficit,leading to the formation of a large area of dry soil layer.Dry soil layer can aggravate the soil water repellency to a certain extent,hinder soil water movement,endanger the biological cycle of terrestrial ecosystem and weaken the water cycle,which has a certain negative effect on the existing vegetation construction achievements.In-depth understanding of soil hydrological process and its response to land use change in the Loess Plateau is of great scientific significance for the sustainable utilization of soil water and reasonable vegetation construction.The prior study on soil water and dry soil layer mostly focused on the limited observation and model simulation of plot scale.However,there are few studies on the long-term changes of deep soil water in the Loess Plateau from the farming period to the vegetation restoration period for decades,which limits the in-depth understanding of the quantitative relationship between soil water and vegetation and the recovery and regulation of dry soil layer.In this paper,the typical loess zone of the Loess Plateau is taken as the study area.Firstly,based on the three soil data sets(deep profile,north-south transect and regional sampling),the pedotransfer functions of soil hydraulic properties(including van Genuchten model parameters,bulk density and saturated hydraulic conductivity)in the study area are established,and the spatial data of deep soil hydraulic properties at the regional scale are obtained.Then,based on the in-situ observation data,the Hydrus-1D model was calibrated to simulate the response process of deep soil water to land use change during nearly one hundred years(1981–2060).Finally,the long-term change process of soil water in the 0–5 m profile from the farming period to the vegetation restoration period was simulated at the regional scale(1981–2014),and the evolution characteristics of hydrological variables such as soil water storage,potential groundwater recharge and evapotranspiration were quantified.The feasibility of regulating dry soil layer based on land use change in the typical grassland zone of the Loess Plateau was quantitatively studied,and the recovery process and main control factors of dry soil layer after the conversion of artificial forest vegetation into natural grassland were discussed.The main research results are as follows :(1)The soil hydraulic properties of 0-8 m profile in the Loess Plateau are closely related to soil texture,climatic conditions and topographic factors.The pedotransfer function equation of soil hydraulic properties constructed by various environmental factors has better simulation ability and prediction accuracy than other pedotransfer functions.Based on the established pedotransfer function model of soil hydraulic properties,combined with the spatial interpolation method,the spatial continuous 0–5 m soil hydraulic parameters(including van Genuchten model parameters(α,n,θr andθs),bulk density and saturated hydraulic conductivity)in the typical loess zone were obtained.We found that the soil hydraulic properties in the Loess Plateau had zonal distribution characteristics,which mainly showed the transition from southeast to northwest,and the south and north showed different patterns.The parameterαdecreases from southwest to north,parameter n decreases from north to south,residual water contentθr decreases from southeast to northwest,saturated water contentθs decreases from west to east.The bulk density was highest in the north,moderate in the south area,and lowest in the middle and west area.The saturated hydraulic conductivity decreases from southwest to east.

Mots clés : Land-use change ;Vegetation restoration ;Soil water ;Soil desiccation ;The Loess Plateau ;

Présentation (CNKI)

Page publiée le 16 octobre 2022