Interannual variations of the grassland boundaries bordering the eastern edges of the Gobi Desert in central Asia

Abstract

The Mongolian Steppe that borders the northern and eastern edges of the Gobi Desert in central Asia is one of the world's largest grasslands, extending across the nation of Mongolia and the Inner Mongolian Autonomous Region (IMAR) of China. Recent findings show that this region has one of the strongest warming signals on Earth since the late 1970s. The objective of this study was to evaluate the relationships between climate and interannual variation of the grassland boundaries in Mongolia and IMAR between 1982 and 1990. The remote sensing data used in this study were the 15–day maximum Normalized Difference Vegetation Index (NDVI) composites derived from the Global Area Coverage of the Advanced Very High Resolution Radiometer (AVHRR). Monthly precipitation, mean monthly temperature, and monthly actual evapotranspiration (AE) were derived from meteorological station records acquired during the study period across the eastern Mongolian Steppe. The occurrence of onset of green–up, as determined with time-series NDVI data, was used to identify vegetated and non-vegetated areas. Great interannual variation of the Gobi boundary position was observed over the study period. This boundary variation was largely controlled by the climate before the growing season (the ‘preseason’ climate). Along the eastern edge of the Gobi desert in central IMAR, preseason AE was the major climatic factor affecting the annual shift of the Gobi boundary, while further north in Mongolia, preseason temperature was the driving climatic factor. Our findings suggest that the response of vegetation communities to climate changes varied as a function of land-use intensity within the ecosystem.

Acknowledgments

The authors acknowledge the financial support provided by the National Science Foundation through Models and Methods for Integrated Assessment Program ATM-0001478. The authors thank Dr Compton Tucker (Biospheric Sciences Branch Laboratory for Terrestrial Physics, NASA Goddard Space Flight Center) for providing the GAC AVHRR dataset. The authors also wish to thank Mr Chenyang Xiao for the discussion with the statistical analysis, and Dr Stephen Egbert, Mr Mike Houts, Dr Mark Jakubauskas, and Dr Mingliang Liu for their help with manuscript review.