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Lanzhou University (2020)

Grassland Vegetation Change and Its Driving Force in the Loess Plateau of China

魏建洲

Titre : Grassland Vegetation Change and Its Driving Force in the Loess Plateau of China

Auteur : 魏建洲;

Grade : Doctoral Dissertation 2020

Université : Lanzhou University

Résumé partiel
The structure and function of grassland ecosystem response sensitively to climate change and human disturbance.Under the background of global warming and intensified human activities,clarifying the law of grassland vegetation change,quantifying the impact of environmental factors on the change of grassland vegetation and identifying the driving factors of the change of grassland vegetation are of a significant importance to understanding the change mechanism of the structure and function of grassland ecosystem and developing effective policies for ecological management and regulation.As an important part of the ecological security barrier in China,the ecological environment of the Loess Plateau is vulnerable.In the past two decades,the ecological environment of the Loess Plateau has improved significantly.However,it remains unclear that what specific factors mainly drive the dynamics of vegetation.Moreover,there is still a lack of understanding the contribution and driving mechanism of key environmental factors to the grassland vegetation activity.In order to clarify the response mechanism of grassland vegetation activities to the changes of environmental factors on the Loess Plateau,in this study,the multi-source vegetation index was used to analyze the characteristics of grassland vegetation changes in the Loess Plateau,the contribution of human activities and climate change to grassland vegetation changes was quantitatively evaluated,the specific factors driving the grassland vegetation changes in the Loess Plateau were identified by building a structural equation model,and the sensitivity of grassland vegetation response to climate change was simulated and analyzed based on the model of grassland aboveground biomass response to climate factor change on the Loess Plateau.Finally,aboveground biomass,coverage,species richness and height were used to characterize grassland vegetation growth activity,and the environmental factors affecting natural(undisturbed)grassland activity were comprehensively attributed by structural equation model on the Loess Plateau.The main results are as follows :(1)The grassland vegetation increased significantly at spatiotemporal scales on the Loess Plateau.Significant correlations(P<0.001)for SPOT-VEGETATION NDVI with the measured coverage,and MOD17A3 NPP with the measured aboveground biomass were detected.It indicated that the above two vegetation indexes were reliable for monitoring the dynamic change of grassland vegetation on the Loess Plateau.

Mots clés : the Loess Plateau; grassland vegetation change; human activities; climate change; above-ground biomass; driving factors; attribution analysis; structural equation model;

Présentation (CNKI)

Page publiée le 3 juin 2021, mise à jour le 22 octobre 2021