Entity

Time filter

Source Type


Zhang G.,Hulun Buir Grassland Ecosystem Observation and Research Station | Zhang G.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Zhang G.,University of Chinese Academy of Sciences | Xu X.,Ministry of Agriculture Key Laboratory of Resource Remote Sensing and Digital Agriculture | And 5 more authors.
Acta Geographica Sinica | Year: 2011

Global warming, a global concern, has led to significant vegetation changes especially in the past 30 years. The Hulun Buir Grassland in Inner Mongolia, one of the world's three prairies, is undergoing a process of prominent warming and drying. It is necessary to investigate the effects of climatic variations (temperature and precipitation) on vegetation changes for a better understanding of acclimation to climatic change. NDVI (Normalized Difference Vegetation Index), which can reflect characteristics of plant growth, vegetation coverage, biomass, and so on, is used as an indicator in monitoring vegetation changes. GIMMS NDVI from 1981 to 2006 and MODIS NDVI from 2000 to 2009 were adopted and integrated in this study to extract the time series characteristics of vegetation change conditions in Hulun Buir. The responses of vegetation coverage changes to climatic variations from the yearly, seasonal and monthly time scales were analyzed combined with temperature and precipitation data of seven meteorological sites. In the past 30 years, vegetation coverage change was closely correlated with climatic factors, and the correlations were different on different time scales. Annual average of vegetation change was better correlated with precipitation, suggesting that rainfall was the main factor for driving vegetation change. Correlations between seasonal average of vegetation coverage and climatic factors showed that the sensitivity of vegetation growth to hydrothermal condition change was different in different seasons. The sensitivity of vegetation growth to temperature in summer was higher than in the other seasons, while that of vegetation growth to rainfall in both summer and autumn was higher, especially in summer. Correlations between monthly average of vegetation coverage and climatic factors during growing seasons showed that the response of vegetation change to temperature in April and May was stronger, indicating that the temperature effect occurred in the early stage of vegetation growth. Correlations between NDVI of the current month and precipitation of the month before the current month were better from May to August, showing a hysteresis response of vegetation growth to rainfall. Grasses turned green and began to grow in April, and the impacts of temperature on grass growth was obvious, therefore, the increase of NDVI in April might be due to an advanced growing season caused by climatic warming. In summary, relationships between annual variation of monthly vegetation and climatic factors represent temporal rhythm controls of temperature and precipitation on grass growth.


Zhang G.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | Zhang G.,University of Chinese Academy of Sciences | Zhang G.,Hulun Buir Grassland Ecosystem Observation and Research Station | Xu X.,CAS Beijing Institute of Geographic Sciences and Nature Resources Research | And 5 more authors.
Journal of Geographical Sciences | Year: 2011

Global warming has led to significant vegetation changes especially in the past 20 years. Hulun Buir Grassland in Inner Mongolia, one of the world's three prairies, is undergoing a process of prominent warming and drying. It is essential to investigate the effects of climatic change (temperature and precipitation) on vegetation dynamics for a better understanding of climatic change. NDVI (Normalized Difference Vegetation Index), reflecting characteristics of plant growth, vegetation coverage and biomass, is used as an indicator to monitor vegetation changes. GIMMS NDVI from 1981 to 2006 and MODIS NDVI from 2000 to 2009 were adopted and integrated in this study to extract the time series characteristics of vegetation changes in Hulun Buir Grassland. The responses of vegetation coverage to climatic change on the yearly, seasonal and monthly scales were analyzed combined with temperature and precipitation data of seven meteorological sites. In the past 30 years, vegetation coverage was more correlated with climatic factors, and the correlations were dependent on the time scales. On an inter-annual scale, vegetation change was better correlated with precipitation, suggesting that rainfall was the main factor for driving vegetation changes. On a seasonal-interannual scale, correlations between vegetation coverage change and climatic factors showed that the sensitivity of vegetation growth to the aqueous and thermal condition changes was different in different seasons. The sensitivity of vegetation growth to temperature in summers was higher than in the other seasons, while its sensitivity to rainfall in both summers and autumns was higher, especially in summers. On a monthly-interannual scale, correlations between vegetation coverage change and climatic factors during growth seasons showed that the response of vegetation changes to temperature in both April and May was stronger. This indicates that the temperature effect occurs in the early stage of vegetation growth. Correlations between vegetation growth and precipitation of the month before the current month, were better from May to August, showing a hysteresis response of vegetation growth to rainfall. Grasses get green and begin to grow in April, and the impacts of temperature on grass growth are obvious. The increase of NDVI in April may be due to climatic warming that leads to an advanced growth season. In summary, relationships between monthly-interannual variations of vegetation coverage and climatic factors represent the temporal rhythm controls of temperature and precipitation on grass growth largely. © 2011 Science China Press and Springer-Verlag Berlin Heidelberg.

Discover hidden collaborations