Spatiotemporal Assessment of Vegetation Trends in the Post-Soviet Central Asia

Abstract

Currently there is a gap of spatially and temporally explicit information on vegetation cover dynamics and trends in the post-Soviet Central Asia at spatial scales sufficient to support decision-making in the region. Insufficient information also exists concerning vegetation variability across climatic gradients as well as vegetation response across different land uses, from natural rangelands to intensively irrigated croplands. We analyzed vegetation cover changes in five Central Asian countries in this study. This analysis included trends in key vegetation phenological parameters derived from 250 m Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) time-series data for 2000–2011. In order to follow the vegetation changes over time, we calculated trends in phenometrics using a robust trend analysis method. The results showed that inter-annual vegetation dynamics followed precipitation patterns only outside irrigated areas, while clearly differentiated winter and summer seasons were observed throughout the study area. Specifically spatial patterns of long-term vegetation trends allowed defining areas characterized by decrease in overall vegetation greenness and peak greenness as well as revealing the shifts in timing of occurrence of peak greenness over the monitoring period. The information obtained will prove as a useful guide in the selection of field sites for detailed vegetation surveys and land rehabilitation interventions as well as improvement of overall understanding of vegetation dynamics and variability in the remote regions of Central Asia.