Vegetation phenology of Northern China from SPOT-VEGETATION and the influence of climate

摘要

This paper demonstrates an empirical link between temperature and vegetation phenology, and environmental changes in vegetation productivity and vegetation phenology in Northern China over 11 years. SPOT Vegetation derived NDVI at 10-day (dekad) temporal resolution was analysed over Northern China from 1998 to 2009. We extracted phenological information from NDVI time-series by deriving three indices: start and end of the growing season, and the time-integrated NDVI as an indicator of seasonal vegetation productivity. In this process, the camelback algorithm (Balzter et al., 2007) was used to define the dates of green-up and dormancy. The derived timing-based phenological matrices in eight Koppen climate classes indicate an overall advance of the start of the growing season and a statistically significant increase in NDVI-based productivity. A regression analysis between corresponding phenological and temperature variables for each year found positive trends in the onset of green-up and negative trends in vegetation dormancy on both pixel and climate-type basis. In nearly all years, the earlier start of the growing season (SOS) is related to warmer weather in the preceding three months, while higher temperatures in the three months before the end of the growing season (EOS) have the effect of delaying EOS.