Revealing climatic impacts on the temporal and spatial variation in vegetation activity across China: Sensitivity and contribution

Relative weakness in sensitivity and contribution integration, especially lack of specific indicators at spatial and temporal scales, may hinder the formation of systematic knowledge for climate change impact on vegetation activity. Considering the interannual variability and periods difference, we investigated the ecosystem sensitivity to hydrothermal conditions and the contribution of individual climatic factors to vegetation activity on spatiotemporal scales during the period of 1980s-2013 in China. We ran simulations of the Common Land Model (CoLM) to obtain the photosynthetic rate, and used the satellite-derived Normalized Difference Vegetation Index (NDVI), to which we applied a temporal sensitivity analysis, the slope change ratio of accumulative quantity (SCRAQ), and geographical detectors. We show that the discrepancy between warming and precipitation variation contributed to vegetation activity was more notable than the ecosystem sensitivity to hydrothermal conditions, regardless of which temporal and spatial scale was considered. The sensitivity of vegetation activity to hydrothermal variation in most parts of northeastern and western China was higher than elsewhere, and the contribution of warming to vegetation dynamics was relatively high in the Inner Mongolian Plateau and Tibetan Plateau (>60%), where the contribution of warming to the vegetation distribution was also greater than elsewhere in China. Conversely, the contribution of precipitation variation to vegetation dynamics was comparatively greater in northwestern China and subtropical and tropical regions (>55%). The spatiotemporal contribution of precipitation variation to vegetation activity differed between regions, especially on the Tibetan Plateau and in subtropical and tropical regions. Moreover, both the temporal and spatial sensitivities to climate change were weak in the subtropical and tropical regions, where the contribution of climatic factors to vegetation distribution was also small. Overall, temperature sensitivity and its contribution to vegetation activity were positively associated in most regions. However, the regions where precipitation contributed substantially to vegetation activity were not necessarily also highly sensitive to changes in precipitation within the range of variation explored.