The effects of climate change on normalized difference vegetation index (NDVI) in the Northeast of Iran

On the basis of land use/land cover map, satellite derived images of NDVI, air temperature and precipitation, the correlations between NDVI-air temperature and NDVI-precipitation over time period of 1987-2016 in inter-annual/monthly scales were analyzed. The present study investigated the relationships between inter-annual/monthly variations of climate features and the fluctuations of NDVI by four vegetation types in Mashhad-Chenaran plain, northeast of Iran. It was revealed that yearly precipitation by all vegetation types has close correlations with NDVI fluctuations. The inter-annual NDVI-precipitation showed that rich ranges were most affected by precipitation, followed by moderate ranges, dry farming and irrigated farming, where the correlation coefficient R varied between 0.419 and 0.488 (P <= 0.05), (P <= 0.01). Furthermore, the correlations between monthly NDVI-air temperature by all vegetation types were remarkably significant. The responses of the NDVI to monthly variations of air temperature exhibited that rich range were most affected by monthly temperature fluctuations followed by dry farming, moderate range, and irrigated farming. Accordingly, the values of correlation coefficient R ranged from 0.769 to 0.845 (P <= 0.01). The finding results confirmed the utility of NDVI index to express vegetation variability in semi-arid climate conditions and improved our knowledge about the relations between climate features and vegetation growth for rehabilitation programs in watershed scale.