Responses of NDVI to climate change in the Hai Basin

Abstract

In this study, based on the RS and GIS systems, AVHRR/NDVI data of 8 km resolution and meteorological data were used to analyze NDVI, annual precipitation, and temperature change rates by pixel from 1981 to 2000. In addition, the correlation between NDVI, annual rainfall, and annual average air temperature were calculated. The results showed that annual precipitation increased in the northern and southern areas of the Hai Basin from 1981 to 2000 while declining in the central area, with a range of-80 to 80 mm/10 a ('a' represents a year). As basin-wide temperatures increased, the Wutai Mountains area had the most significant increase, up to about 2℃/10 a. The NDVI reduced significantly in Beijing, Tianjin and other large adjacent cities, with a change rate of about-0.8 NDVI/10 a while increasing in the southeast part of the plains of the Hai Basin and the Yanshan Mountains, at about 0.8 NDVI/10 a. The correlation between NDVI, precipitation, and air temperature had significant spatial variation. In the cold and wet areas of the Hai Basin, such as the grasslands in the upstream areas of the Luanhe River and the area of the Wutai Mountains, the vegetation index is not sensitive to precipitation while it is correlated positively with the air temperature. In the warm and wet climate areas, such as the south end of the Taihang Mountains, the precipitation affected vegetation growth when it increased. In dry conditions, such as the eastern coastal plain and north of the Yanshan Mountains of the Hai Basin, NDVI significantly was correlated positively with precipitation and negatively with air temperature. In the irrigated agriculture areas of the piedmont plain, crop growth was not sensitive to climate changes.