Variations in satellite-derived phenology in China's temperate vegetation

The relationship between vegetation phenology and climate is a crucial topic in global change research because it indicates dynamic responses of terrestrial ecosystems to climate changes. In this study, we investigate the possible impact of recent climate changes on growing season duration in the temperate vegetation of China, using the advanced very high resolution radiometer (AVHRR)/normalized difference vegetation index (NDVI) biweekly time-series data collected from January 1982 to December 1999 and concurrent mean temperature and precipitation data. The results show that over the study period, the growing season duration has lengthened by 1.16 days yr(-1) in temperate region of China. The green-up of vegetation has advanced in spring by 0.79 days yr(-1) and the dormancy delayed in autumn by 0.37 days yr(-1). The dates of onset for phenological events are most significantly related with the mean temperature during the preceding 2-3 months. A warming in the early spring (March to early May) by 1 degrees C could cause an earlier onset of green-up of 7.5 days, whereas the same increase of mean temperature during autumn (mid-August through early October) could lead to a delay of 3.8 days in vegetation dormancy. Variations in precipitation also influenced the duration of growing season, but such influence differed among vegetation types and phenological phases.