COMPARATIVE ANALYSIS ON RESPONSES OF VEGETATION PRODUCTIVITY RELATIVE TO DIFFERENT DROUGHT MONITOR PATTERNS IN KARST REGIONS OF SOUTHWESTERN CHINA

The climate conditions are complex and diverse in Southwest China (SWC), especially the karst area, and the interaction between climate change and terrestrial ecosystems has become complex. Vegetation productivity is an important indicator in terrestrial ecosystems, and can visually reveal the impacts of extreme climate. Drought affects not only the process of photosynthesis directly, but also the changes in vegetation productivity from other forms of interference with photosynthesis. Against this background, we analyzed the time series and spatial distribution characteristics of drought, the temporal and spatial distribution and anomalies of vegetation productivity. For the observation period 2001-2012, we used different drought monitor patterns (including Pa, SPI, SPEI and PDSI) to assess the impact of drought on vegetation productivity (annual NPP and monthly GPP). We mainly want to explore the response of different monitor patterns to vegetation productivity at different stages. NPP exhibited considerable variation during 2001-2012; the droughts in 2009 and 2010 led to NPP reduction by 14.7% and 8.4%, respectively. The NPP is directly proportional to the severity of drought, severe drought had a greater impact on monthly GPP than mild drought, especially for evergreen forests, shrublands, and deciduous forests, while little variation was found for croplands. We compared drought indices-vegetation productivity during the drought season between 2009 and 2010; SPEI has a better correlation with SPI and PDSI. The results demonstrate that SPEI and PDSI are most capable of monitoring the vegetation drought conditions. There will be large differences of the influence on vegetation productivity on different drought levels. Our findings suggested that multi-indices in drought monitoring are needed in order to acquire robust conclusions.