Abstract
Temperature and water conditions affect vegetation growth dynamics and associated spectral measures. We examined the response of the growing season maximum enhanced vegetation index (MEVI) to the growing season temperature, precipitation, vapor pressure and relative humidity on the Tibetan Plateau. The responses of the MEVI to climatic factors changed with the vegetation type, which may be attributed to the finding that the background values and climatic factor changes varied with the type of vegetation. The spatially averaged MEVI over the entire plateau exhibited a non-significant decreasing trend. Approximately 5% and 12% of the vegetation area exhibited significant MEVI decreasing and increasing trends, respectively. Both vapor pressure and relative humidity significantly affected the MEVI, whereas the temperature and precipitation did not significantly correlate with the MEVI over the entire plateau. Specifically, the environmental humidity dominated the MEVI variation over the entire plateau.
Highlights
Vegetation indices, which indicate vegetation growth conditions, have been widely applied for estimating vegetation biomass and coverage [1,2,3,4,5], determining vegetation phenology [6,7] and spatially extrapolating ecosystem carbon flux [8,9,10,11,12]
In this study, based on climatic data and enhanced vegetation indices from 2000–2012 on the Tibetan Plateau, we used a trend analysis to analyze the changes in the growing season maximum enhanced vegetation index (MEVI), temperature and water conditions, and we used a correlation analysis to analyze the relationship between the MEVI and climatic factors
This is the first study that has analyzed the correlations between the enhanced vegetation index and the temperature, precipitation and, especially, humidity for different types of vegetation on the Tibetan Plateau
Summary
Vegetation indices (e.g., the normalized difference vegetation index, NDVI), which indicate vegetation growth conditions, have been widely applied for estimating vegetation biomass and coverage [1,2,3,4,5], determining vegetation phenology [6,7] and spatially extrapolating ecosystem carbon flux [8,9,10,11,12]. Many studies have analyzed NDVI variations and their relationships with temperature and precipitation on the Tibetan Plateau, but no consistent correlations between NDVI and climatic factors have been observed [1,19,20]. Zhang et al [6] demonstrated that warming beneficially affects alpine vegetation growth. Both Fu et al [1] and Zhang et al [21] found that warming adversely affects grassland growth. Many studies have shown that precipitation positively correlates with NDVI [20,22], Zhang et al [21] found negative relationships between NDVI and precipitation at certain specific sites on the Tibetan Plateau. The NDVI has certain disadvantages in vegetation analyses, such as band saturation, especially in areas with high vegetation coverage [13,23]
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