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Guizhou Normal University (2021)

The Desertification Hydro-process and Carbon and Nitrogen Loss in a Typical Catchment of the Karst Plateau-Gorge

李渊

Titre : The Desertification Hydro-process and Carbon and Nitrogen Loss in a Typical Catchment of the Karst Plateau-Gorge

Auteur : 李渊

Grade : Doctoral Dissertation 2021

Université : Guizhou Normal University

Résumé partiel
Karst rocky desertification in southern China is an extreme phenomenon of soil erosion and ecological degradation caused by karst hydrological process.The high heterogeneity of rocky desertification environment and complex hydrological structure limit the understanding of hydrological process and runoff generation,resulting in insufficient understanding of the mechanism of water and soil loss.The study of hydrological process and nutrient loss in rocky desertification area is the scientific basis of soil and water conservation,which is of great significance to the sustainable development of social economy.According to the theory of karst landform development,hydrological structure,hydrological cycle and stable isotope of hydrogen and oxygen,aiming at the scientific issue of how the typical rocky desertification environment affects the hydrological process of binary hydrological structure,the Dingtan catchment is selected as the research area in Zhenfeng-Guanling Karst Plateau Gorge area,which represents the overall structure of karst rocky desertification environment in southern China.Based on the geomorphological and hydrological structure of the catchment,through the positioning observation of the meteorological hydrology,runoff plot hydrology,fissure hydrology and catchment hydrology,combined with the stable isotope technology,the data analysis methods such as wavelet coherence analysis and binary mixed model are used,the characteristics of carbon and nitrogen loss and hydrological processes in slope,fissure and catchment were studied.This paper focuses on revealing the hydrological process and carbon and nitrogen loss mechanism of karst rocky desertification,so as to provide scientific basis for the optimal regulation of water and soil resources and ecological restoration.Firstly,the spatiotemporal dynamics of soil moisture in slope surface and its influencing factors,the effects of different vegetation types on hydrological processes of surface flow and interflow,runoff and sediment yield,and the effects of runoff processes on carbon and nitrogen migration and loss were revealed.The results show that the soil moisutre in the runoff plot increases gradually with the top to bottom of slopes.The soil moisture in different slope positions and different vegetation types has time stability,especially in rainy season.However,the difference of vegetation type and coverage will lead to short-term temporal instability of soil water in dry season.Most of the rainfall is loss on the slope by seepage.Deep seepage and interflow are the main runoff generation and loss paths.The proportion of rainfall loss through slope runoff is low(<10%) ;the rainfall loss is mainly through underground leakage(>40%).Drought interval and field capacity are the main factors affecting the proportion of soil water storage.The slope runoff mainly comes from the interflow,but the contribution of different depth and slope position to the runoff plots of different types was significantly different.Vegetation coverage and rainfall are the controlling factors of runoff and sediment yield.Most of the soil loss caused by rainfall erosion comes from the surface soil.The runoff generation process on the slope has a certain impact on the nutrient loss,and the amount of carbon and nitrogen loss varies with rainfall.There was a positive correlation between DOC and TSN in runoff.The loss of DOC and TSN was positively correlated with runoff,but not with rainfall.

Mots clés : karst ;plateau-gorge ;rocky desertification ;hydrological process ;carbon and nitrogen loss ;

Présentation (CNKI)

Page publiée le 23 octobre 2021