| 摘 要： |
Vegetation dynamics are key processes which present the ecology system's response to climate change. However, vegetation sensitivity to climate change remains controversial. This study redefined vegetation sensitivity to precipitation (VSP) and vegetation sensitivity to temperature (VST) by the coefficient of determination (R-2) obtained by a linear regression analysis between climate and the normalized difference vegetation index (NDVI), as well as by using an analysis of variance to explore the significant differences between them in different seasons from 1982 to 2013, and exploring the general changed rules of VSP/VST on a timescale. Moreover, the variations in VSP and VST across the Tibetan Plateau were plotted by regression analysis. Finally, we used structural equation modeling (SEM) to verify the hypothesis that the respondence of VSP and VST to the NDVI was regulated by the hydrothermal conditions. Our results showed that: (1) the annual VSP increased in both spring and winter (R-2 = 0.32, p < 0.001; R-2 = 0.25, p < 0.001, respectively), while the annual VST decreased in summer (R-2 = 0.21, p < 0.001); (2) the threshold conditions of seasonal VSP and seasonal VST were captured in the 4-12 mm range (monthly precipitation) and at 0 degrees C (monthly average temperature), respectively; (3) the SEM demonstrated that climate change has significant direct effects on VSP only in spring and winter and on VST only in summer (path coefficient of -0.554, 0.478, and -0.428, respectively). In summary, our findings highlighted that climate change under these threshold conditions would lead to a variation in the sensitivity of the NDVI to seasonal precipitation and temperature. |
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