Changes in Growth of Spring Precipitation-Dominated Vegetation in the Great Lakes Region of Central Asia Over the Period 1982–2015

The Great Lakes region of Central Asia (GLRCA) is the largest dryland in the middle temperate zone of the northern hemisphere and is characterized by precipitation occurring mainly in spring. However, little attention has been paid to the response of vegetation growth to spring climate change in the GLRCA. In this study we used the satellite-derived Normalized Difference Vegetation Index (NDVI) and climate data from 1982 to 2015 to analyze the spatial and temporal variation in spring (March, April, and May) vegetation and the impacts of changes in spring precipitation, temperature, and drought on vegetation growth over the GLRCA. A piecewise linear regression model indicated a turning point (TP) in spring NDVI trend for the year 1999 at a regional scale, with an increasing trend before the TP but a decreasing trend following the TP. Spatially, the TP of spring NDVI trend and the major climate factors driving vegetation growth were found to vary among regions. Before and after the TP in spring NDVI we found that the spatial pattern in the trend of increase in precipitation was relatively consistent with the trend of increase in the NDVI in the southern regions, which are dominated by spring precipitation. However, in the northern regions (dominated by summer precipitation) the spatial pattern of the trend of increase in temperature was more consistent with the trend of increase in the NDVI. Results indicated that spring vegetation response to temperature is more sensitive in the regions dominated by summer precipitation, while the response to precipitation is more sensitive in the regions dominated by spring precipitation. Additionally, we found that the influence of spring precipitation on the annual maximum NDVI was greater than that in spring NDVI, suggesting a lag in the effect of precipitation on vegetation growth