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Northwest Agriculture and Forestry University (2019)

Spatio-temporal Variations of Vegetation Cover and Its Relationships between Climate Change and Human Activities Over China


Titre : Spatio-temporal Variations of Vegetation Cover and Its Relationships between Climate Change and Human Activities Over China

Auteur : 金凯;

Grade : Doctoral Dissertation 2019

Université : Northwest Agriculture and Forestry University

Résumé partiel
Society and economy as well as the ecological environment we depend on have been critically influenced by global warming in recent decades.As one of the most important parts in the terrestrial ecosystem,vegetation provides a wide range of ecological funct ions such as storm prevention,sand immobilization,soil and water conservation,and climate regulation.Vegetation cover change is very complicated in China due to rapid growth of national economy and population,increasing impact of human activities on the vegetation ecosystem and the regional difference of climate change.It is necessary to understand the spatio-temporal variation of vegetation cover and scientifically analyze the interaction between vegetation,climate,and human activities,which can contribute to the formulation and implementation of the national strategy for ecologically sustainable development.However,the current studies differ greatly in the research scale,region,and period,and the attribution analysis of the national vegetation cover change needs further investigation.Therefore,based on the long-term data of climate,land use,and Normalized Difference Vegetation Index(NDVI)datasets and various methods of Kriging interpolation,trend analysis,coefficient of variation,correlation analysis,multiple regression and residual analysis,this study explored the changes of climate,land use,and vegetation cover in China from 1982 to 2015 at varied spatiotemporal scales,and then evaluated the drivers of vegetation cover change and their contributions.Finally,we analyzed the impacts of land surface processes dominated by vegetation cover change on surface air temperature in the Loess Plateau where vegetation cover has been undergone significant restoration with a widely-used OMR method(Observation Minus Reanalysis)worldwide.The main conclusions of this study are as follows :(1)Climate warming in China is significant during 1982-2015 and the average increasing trend of annual mean temperature is about 0.35℃/10a(P<0.01).The change rates of annual mean temperature varies in each region,and it has a clear decline in the eight vegetation sub-regions as follows:Qinghai-Tibet Plateau alpine meadow region(V8),Temperate desert region(V7),Temperate grassland region(V6),Evergreen broadleaf forest region(V4),Deciduous broadleaf forest region(V3),Rainforest region(V5),Broadleaf–coniferous mixed forest region(V2)and Coniferous forest region(V1).While the annual total precipitation showed an unobvious trend in China,it increased the fastest in V5 and decreased the fastest in V1.Moreover,the seasonal temperature and precipitation generally showed certain interdecadal variations in China,whereas their overall change trends showed great spatial heterogeneity.On average,seasonal mean temperature increased rapidly before 1998,and then increased slowly,and even decreased in winter ;precipitation in autumn decreased obviously before 1998,and then increased obviously,which was contrary to the change of precipitation in summer.In recent 34 years,the temperature in spring showed the fastest increase,while the temperature in winter showed the slowest increase ;there was no significant change in precipitation in each season.At the provincial scale,while the annual mean temperature showed the fastest increase in Shanxi,it showed the slowest increase in Hainan ;while the annual total precipitation showed the fastest increase in Hainan,it showed the fastest decrease in Hubei.In general,while the climate in most areas of northwestern and southeastern China showed a warming and humid trend,it showed a warming and drying trend in the strips extending from the northeastern to the southwestern.

Mots clés : China; NDVI; vegetation cover; climate change; land use; human activities;

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Page publiée le 5 mai 2020