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Université de Mongolie-Intérieure (2017)

Vegetation Dynamics and Its Response to Climate Change in Arid and Semi-arid Areas

苗百岭;

Titre : Vegetation Dynamics and Its Response to Climate Change in Arid and Semi-arid Areas

Auteur : 苗百岭;

Grade : Doctoral Dissertation 2017

Université : Université de Mongolie-Intérieure

Résumé
The impact and feedback of climate change on terrestrial ecosystems is an important part and issue in global change research.The arid and semi-arid areas are sensitive regions of global climate change.In this paper,the NDVI data from 1982 to 2011,the long-term dynamic monitoring data of above-ground biomass of typical grassland communities from 1982 to 2015,the plant phenology observation data of grassland in 2004-2003 and their corresponding climate date were used to analyze the impact of climate change on the key functions and processes of ecosystems such as phenology,productivity,stability and inter-specific relationships in arid and semi-arid ecosystems.This study will provide examples of research on the global response and adaptation to climate change in arid and semi-arid ecosystems,as well as provide theoretical and data support for adaptive management,sustainable use and conservation of ecosystem responses to climate change in arid and semi-arid areas.The main result were drawn as follows:1.In 2004 and 2013,the annual mean temperature of Inner Mongolia grassland did not change significantly,and the annual precipitation increased slightly.The start of the growing season(SOS)slightly ahead of time,the end of the growing season(EOS)was significantly pushed after which extend the growing season.The start of the growing season of plants in the meadow steppe,typical steppe and desert steppe was shift to an earlier date 2.04 d/10a,4.01 d/10a and 1.32 d/10a,respectively.The end of the growing season was delayed 12.68 d/10a,10.35 d/10a and 9.58 d/10a in the meadow steppe,typical steppe and desert steppe respectively ;the growth season was prolonged by 14.72 d/10a,14.36 d/10a and 10.90 d/10a,respectively.The temperature is the main limiting factor of the start of the growing season in the grassland area.The change trend of the growing season and the daily mean temperature are stabilized through the average temperature of 0℃-10℃,the number of days between 0℃ and 10℃ is stabilized,Basically the same.The climatic mechanism that affects the end of the growing season of plants is complicated,and the degree of matching of water and heat determines the advance or delay of the plant growing season.2.The natural vegetation NDVI of the Inner Mongolia Plateau in 1982-2011 did not change significantly,but it had obvious five-year stage fluctuation characteristics.The natural vegetation NDVI in 1982-1986,in 1992-1996,and in 2007-2011 all showed an upward trend in the whole region.There was a slight downward trend in the natural vegetation NDVI in 1997-2001,and in 2002-2006,the maximum value of natural vegetation NDVI in the past 30 years was appears in 1992-1996,while the minimum value of NDVI appears in 1997-2001.But the variation of vegetation NDVI in different vegetation types was slightly different.3.Drought frequency,intensity and occurrence range have increased between 1982 and 2011,especially in summer and autumn.The effect of drought on vegetation productivity has significant temporal and spatial heterogeneity:the response of typical steppe and desert steppe to drought is intense with the decrease of NDVI is larger,while the decrease of NDVI in forest,meadow steppe and desert is small.The typical grassland and desert grassland are more sensitive to summer drought,and forest and meadow grassland are more susceptible to spring drought.The five vegetation types showed a lag time of 1-2 months to drought in the spring and summer.4.The precipitation fluctuation characteristics of typical steppe in Inner Mongolia during the period from 1982 to 2015 were significant,mainly in the concentration of precipitation decreased significantly ;small precipitation events(≤5 mm)increased significantly ;inter-annual fluctuations of continuous days without precipitation increase.5.Precipitation fluctuation cause a change in the time of functional groups reach the peak biomass,which increase asynchronous.The time reach the peak of biomass of perennial rhizome grasses,perennial forbs and shrubs is slightly ahead of time,while the time reach the peak of biomass of perennial bunch grasses,semi-shrubs and annuals and biennials is delayed.Although the fluctuation of functional groups’ peak biomass increased,the stability of perennial rhizome grasses,perennial forbs and perennial bunch grasses which was the dominant functional group is still high,leading to the high stability of the whole community,thus can well adapt to climate fluctuations

Mots clés : climate change; plant phenology; vegetation productivity; drought; species asynchrony; community stability;

Présentation (CNKI)

Page publiée le 12 juin 2019