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Inner Mongolia University (2022)

Mechanism between Ecological Processes of Vegetatiion and Their Hydrological Response in Semi-arid Watersheds

于晓雯

Titre : Mechanism between Ecological Processes of Vegetatiion and Their Hydrological Response in Semi-arid Watersheds

Auteur : 于晓雯

Grade : Doctoral Dissertation 2021

Université : Inner Mongolia University

Résumé partiel
The study of vegetation and the hydrological response mechanism is an area which has recently received a great deal of interest as part of the study of the eco-hydrological processes in watersheds,especially in China.In order to prevent siltation of the Yellow River,and to reduce soil erosion and ensure the ecological security of its basin,a large number of ecological projects such as vegetation restoration and small watershed management programs have been conducted in the Loess Plateau area of China since the 1990s.Within this key management area are the ten major Kongtus(tributaries)on the right bank of the Inner Mongolian section of the Yellow River.The understanding of water transport pathways and patterns between vegetation-soil-surface water-groundwater is essential to accurately assess the response mechanisms between vegetation and hydrological processes in typical watersheds in arid and semi-arid regions.This is of particular importance for ecological restoration and watershed management projects,and is necessary to reveal the eco-hydrological response relationships in these watersheds for rational water resources utilization.In this study,the relationship between vegetation and hydrological feedback was examined at different scales from the sample site to the basin.Xiliugou,one of the ten major hole-tunnels in the Inner Mongolia section of the Yellow River,was used as the main study area,and the Wulagai River,a typical inland river in Inner Mongolia,was used as the comparison basin.The spatial distribution and composition of vegetation species in the riparian zone were clarified through a sample site survey,and the response of soil factors to the above-ground biomass and biodiversity of the community was investigated using Person correlation coeffcient analysis and structural equation modeling.This was used to clarify the common characteristics of soil factors affecting above-ground biomass and species diversity.Accordingly,stable hydrogen and oxygen isotope techniques and water chemistry analysis were applied to study dominants.As parts of this study,the water use strategy of dominant species(e.g.,shrubs and herbs),the transformation relationships between groundwater and surface water,and formation mechanisms,were investigated using stable hydrogen-oxygen isotope techniques and hydrochemical analysis of the water transport patterns in the region.The primary conclusions of this study are as follows.1)Grassland vegetation was dominant in the Xiliugou and Wulagai River basins,and the dominant vegetation in the riparian zone was primarily graminoid communities.Additionally,both the above-ground biomass and species diversity of the communities tended to decrease with increasing distance from the river.In the Xiliugou watershed,When the sampling depth is 10 cm,factors affecting vegetation characteristics were total phosphorus and total organic carbon,while total nitrogen played a key role in the sampling depth is 100 cm.Different moisture gradients led to differences in surface soil factors affecting community characteristics,but soil water content was always found to be positively correlated with the above-ground biomass of the community,and could affect above-ground community biomass directly(λ=0.2627,P<0.05)and indirectly by affecting species diversity(λ=0.7669,P<0.001).2)Both the Xiliugou and Wulagai river basins were initially supplied with water from atmospheric precipitation,and groundwaterδD andδ18O values were lower compared to soil water and surface water due to evaporation,water vapor source,altitude,and latitude.It is noteworthy that the hydrogen and oxygen isotope values of all water bodies in the Wulagai basin were greater than those in the Xiliugou basin.Soil water in the riparian zone is recharged by surface water and groundwater,and the hydrogen and oxygen isotopes of deep soil water were more stable

Mots clés : Semi-arid zone watersheds ;Riparian zone vegetation ;Ecohydrological processes ;Stable hydrogen and oxygen isotopes ;HEIFLOW model ;

Présentation (CNKI) https://oversea.cnki.net/KCMS/detai...

Page publiée le 17 octobre 2022