| Abstract: | The satellite-based vegetation condition index (VCI) and temperature conditionindex (TCI) have been used extensively for drought detection and tracking, the assessment ofweather impacts on vegetation and evaluation of the health and productivity of vegetation. Inthis study, in order to detect and monitor the growth condition of vegetation, we have collecteddata on vegetation indices and land surface temperature derived from MODIS (2001-2012)and defined a vegetation health index (VHI) based on VCI and TCI for assessing vegetationhealth condition in the Three Gorges Area, China (TGA). The results of the study show thattemporal and spatial characteristics of vegetation health condition can be detected, tracked andmapped by the VHI index. In most parts of the TGA, the vegetation health condition showedan overall increasing trend during the study period, especially in Wulong, Fengdu, Shizhu andother regions located in the midstream sections of the Three Gorges Reservoir. In addition,the four studied vegetation types all showed clear increasing trends during the study period.The increasing trend in the vegetation health condition shows a strong positive correlationwith topographical slope and altitude (below 500 m). Over the seasons, this trend is strongestin autumn, followed by spring. However, the correlations between vegetation health conditionand climatic factors are more frequently significant in summer and winter than in autumnand spring. The vegetation health condition has been low in 2006 and 2011. This findingis consistent with the extreme weather conditions in those two years. However, only in thesummer is vegetation health condition significantly correlated with three climatic factors inmost of the study area. This result implies that vegetation growth may show a lagged responseto climatic factors and may also be affected by human activities, including agriculturalactivities, industrial activities and other economic activities. |
