Contributions of climatic and anthropogenic drivers to vegetation dynamics indicated by NDVI in a large dam-reservoir-river system

Abstract

With the cascade hydropower stations (CHSs) development and climate change in a large dam-reservoir-river (DRR) system, distinguishing the impact of climatic and anthropogenic factors on vegetation dynamics is vital for a sustainable watershed ecosystem management. In this study, a Breaks for Additive Seasonal and Trend (BFAST) algorithm was adopted to detect the breakpoints (BP) and trend change of climatic factors (CFs) and vegetation dynamics at the pixel scale in the DRR system. The partial correlation and time lag analysis methods were chosen to examine the relationship between vegetation dynamics and CFs (i.e., temperature and precipitation). The multiple linear regression analysis method was adopted to separate the impacts of climatic and anthropogenic factors on vegetation dynamics in multiple periods (i.e., from 1999 to 2013, before BP (BBP), and after BP (ABP)). The most significant results indicated that the area fraction of the BP of vegetation dynamics was 19% of the basin, and the trend BP mainly occurred in 2008. The trend of BP mainly was positive BBP and negative ABP in the basin, and its area fraction was 53.01%. For the eight CHSs, the vegetation dynamics around Ludila and Guanyinyan were more affected by their constructions than that around the other hydropower stations. For the CFs, the vegetation dynamics was mainly affected by precipitation. The lag periods of temperature and precipitation on vegetation dynamics were four months and one month, respectively. Most of the vegetation dynamics appeared to have been impacted by anthropogenic factors in the DRR system. For the eight CHSs, the impact degree of anthropogenic factors on vegetation dynamics BBP was more severe than that ABP, especially around Ludila and Guanyinyan hydropower stations. These results are beneficial for sustainable watershed ecosystem management in the DRR system and ecological development planning around the CHSs.