Background: The ecosystems and natural environment of the Source Region of Yangtze River (SRYR) is highly susceptible to the climate change. Quantifying the response of vegetation Net Primary Productivity (NPP) to the changes of hydrothermal conditions is an important way to identify and predict global ecosystem dynamics.
Methods: Using MODIS/Terra Yearly NPP data at 1km×1km spatial resolution, the spatial-temporal variation of NPP was analyzed at first. Then, correlations between NPP and hydrothermal conditions were evaluated with soil water content and accumulated temperature. Finally, a response model was built to analyze the sensitivity of the NPP to precipitation and temperature changes.
Result: (1) NPP is generally lower in the western SRYR and increases gradually toward the east, with an average value of 85.2 gC/m 2 . The total NPP had increased by 1.42TgC per year from 2000 to 2014. The fastest change rate of NPP is presented in the Downstream region, followed by the middle stream region and Dam River Basin; (2) the NPP of one specific year has obvious relationship with the accumulated temperature of the same year and the soil water deficit of the previous year. The temperature is the dominant climate factor impacting vegetation growth in the SRYR; (3) It is shown an increase of NPP by 0.194 TgC (nearly 30%) with a 1-°C increase in annual mean temperature. While a 10% increase in annual precipitation corresponds to an increase in NPP by 0.517 TgC (nearly 5%).
Conclusion: A warming, wetting and greening SRYR was detected in recent decade. The NPP in SRYR is more sensitive to changes in temperature than changes in precipitation.