Terrestrial vegetation dynamics are closely influenced by both climate and by both climate and by land use and/or land cover change (LULCC) caused by human activities. However, it can be difficult to separate the effects of climate change from ULCC on vegetation.
Recently, researchers in Dr. SHEN Yanjun’s group from the Center for Agricultural Resources Research, Institute of Genetics and Development Biology, the Chinese Academy of Sciences, attempted to attribute trends in the fractional green vegetation cover to climate variability and to human activity in Ejina Region, a hyper-arid landlocked region in northwest China. Through linear difference model, the satellite-observed vegetation coverage change was separated into the fractional vegetation cover and area changes of the desert vegetation and irrigated-oasis. Therefore, their related water availabilities both from precipitation and irrigation can be used to explain the regional fractional vegetation cover.
They found that the fractional vegetation cover in this hyper-arid region was very low but that the mean growing season vegetation cover had increased since the Ecological Water Conveyance Project (EWCP) was launched in 2000. The largest contribution to the overall greening was due to changes in green vegetation cover of the extensive desert areas related with climatic variability with a smaller contribution due to changes in the area of irrigated land (96%). Through comprehensive analysis with different precipitation data sources, they found that the greening of the desert was associated with increases in regional precipitation. Their also reported that the area of land irrigated each year could be predicted using the runoff gauged 1 year earlier.
Taken together, water availability both from precipitation in the desert and runoff inflow for the irrigation agricultural lands could explain about 45%-62% of the total variance in regional vegetation cover from 2000 to 2010. Such results informed management on the implications for water allocation between oases in the middle and lower reaches and for water management in the Ejina oasis.
This work has been published in Hydrology and Earth System Sciences on 9 September, 2014. This study was supported by the National Program on Key Basic Research Project of China (2010CB951003).
AUTHOR CONTACT:
SHEN Yanjun, Group Leader
Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
