Inter-Annual Changes in Vegetation Activities and Their Relationship to Temperature and Precipitation in Central Asia from 1982 to 2003

Abstract

ABSTRACT. We analyzed inter-annual trends in annual and seasonal vegetation activities in Central Asia from 1982 to 2003 and their correlation to climate variability using the NOAA/AVHRR Normalized Difference Vegetation Index (NDVI) dataset and a gridded climate dataset. The results indicate a significant increase in NDVI with a value of 11.35% over the growing season during the 22-year period. Totalled over the entire vegetated area, about 35% of all pixels exhibited significant upward trend in growing season NDVI. We found that NDVI increase in spring was the main contributor to the general upward trend, the spring NDVI increased in more than 50% of all pixels and showed an average value of 13.58%. Correlation analysis indicated a gradual rise in temperature as the only factor controlling trend in spring NDVI. Significant increase in vegetation activity was also identified for summer season, but its amplitude (9.23%) and comprising area (25.13% of all vegetated pixels) were less than for spring. Downward trends in growing season NDVI occurred in 2.17% of the total vegetated area. The greening trends of spring, growing season and summer NDVI strongly related with the climatic parameters: for each land cover type, we found significant correlation with spring temperature and total precipitation; 75% of all upward trends in growing season NDVI were explained by the combination of these both variables. We found that the NDVI trends and their climatic correlates demonstrate great spatial variability at the scale of individual land cover types and at per-pixel scale and proofed that the land use change caused by the constitutional change in the 1991 has substantial control on the vegetation trends. Increased vegetation growth indicated through the analysis of NOAA AVHRR NDVI time-series suggests an increasing carbon stock in biomass of ecosystems in Central Asia.

Modeling Net Ecosystem Exchange for Grassland in Central Kazakhstan by Combining Remote Sensing and Field Data

“…As the steppe grassland occupies territories with significantly higher precipitation amount, the conditions for vegetation growth are much better. It is well known that, because precipitation is the major limiting factor for vegetation growth in drylands, it controls strongly the spatial patterns in vegetation [35,58,59]. Within the short grassland, there is a distinct gradient in the distribution of GPP and NPP from South to North.…”

“…During droughty months in summer (July and early August) their rate of development is hindered. This period of semi-dormancy occurs throughout the study region [34,35].…”

Economics of Land Degradation and Improvement in Uzbekistan

“…Spatial cropping patterns were observed in the Horazm region in Uzbekistan (Conrad et al 2011(Conrad et al , 2014. Inter-annual changes in vegetation activities and their relationship to temperature and precipitation in Central Asia from 1982 to 2003 were analyzed by Propastin et al (2008). Yet cropland degradation per se and the relevant aspects for assessing, for instance, relations between the degradation and their possible drivers have not been studied within quantitative data-based frameworks in Uzbekistan.…”

SPOT-Based Sub-Field Level Monitoring of Vegetation Cover Dynamics: A Case of Irrigated Croplands

“…For example, spatial and temporal LD patterns were analyzed over the Ust-Urt Plateau in Kazakhstan using Landsat images and geostatistical methods [11]. Inter-annual changes in vegetation dynamics and their relationship to temperature and precipitation conditions in Central Asia were studied for the 1982-2003 period by Propastin et al [12]. De Beurs and Henebry [13] assessed LULC changes in Kazakhstan during the periods of 1985-1988 and 1995-1999 using a normalized difference vegetation index (NDVI) satellite time series derived from Advanced Very High Resolution Radiometer (AVHRR) data.…”