Temporal responses of vegetation to climatic factors in Kazakhstan and Middle Asia
Propastin, Pavel P., Martin Kappas and Nadiya R. Muratova
Normalized Difference Vegetation Index (NDVI) is generally recognized as a good indicator of terrestial vegetation productivity. Understanding climatic influences, in particular precipitation and temperature, on NDVI enables prediction of productivity changes under different climatic conditions. We combined a NOAA/AVHRR NDVI dataset and a gridded climate dataset to analyse inter-annual and within-season relationship between NDVI and two ecoclimatic parameters (precipitation and temperature) in Kazakhstan and Middle Asia for the time-period 1981-1998. Evaluation of within-season relationship was based on monthly values of NDVI and climatic parameters during the growing season (April-October), while for evaluation of inter-annual relationship were taken either mean growing season values or mean values over the individual seasons (spring, summer, autumn). The results indicate that a strong correlation exists between NDVI and the two climatic parameters at inter-annual and within-seasonal scales. Temperature was the leading climatic factor controlling both interannual and within-season NDVI dynamics. The dynamic of vegetation activities over the period 1982-1998 was found to be strongly predicted by dynamic of annual precipitation and mean temperature over spring. For semi-desert and steppe vegetation, the inter-annual NDVIprecipitation correlation was higher when precipitation was accumulated over the current year with one-two preceding years, while the within-season dynamic displays a response time of NDVI to precipitation of 1-2 months. The correlation coefficients between NDVI-rainfall and NDVI-temperature exhibit a clear structure in terms of spatial distribution. The results indicate that the response of vegetation to climatic factors increases in order from forest, to semi-desert and steppe, to desert and shrubs vegetation. The correlation coefficients associated with cultural vegetation, especially in areas of irrigation agriculture, as well as the correlation coefficients associated with degrading regions depend on a number of other factors such as type and intensity of irrigation or cropping practice.
Event: XXIII International FIG Congress : Shaping the change
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