PROGRESS IN GEOGRAPHY ›› 2012, Vol. 31 ›› Issue (11): 1433-1442.doi: 10.11820/dlkxjz.2012.11.003

• Original Articles • Previous Articles     Next Articles

Assessment and Intercomparison of Satellite-derived Start-of-Season (SOS) Measures in Eurasia for 1982-2006

LIU Lingling1,2, LIU Liangyun1, HU Yong1,2   

  1. 1. Center for Earth Observation and Digital Earth, CAS, Beijing 100094, China;
    2. Graduate University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2011-11-01 Revised:2012-04-01 Online:2012-11-25 Published:2012-11-25

Abstract: Vegetation phenology is one of the most direct and sensitive indicators of seasonal and interanual variations of environmental conditions. Phenological changes reflect quick change of terrestrial ecosystems in response to climate change. Satellite remote-sensing techniques capture canopy reflectance and can be used for studies of vegetation phenology. In this study, satellite-derived Start of Season (SOS) dates are obtained from the GIMMS AVHRR NDVI dataset by different methods such as Dynamic Threshold method, Delayed Moving Average methods, Double Logistic analysis and Savitzky-Golay method. The derived SOS data are compared and analyzed for the ecoregions from China to Russia, and the Dynamic Threshold method is decided to be most suitable for Eurasia scale. Based on the analysis of the changes of vegetation phenology and the response of phenology to climate change from 1982 to 2006, it is concluded that the Dynamic Threshold method has high retrieval rate for the SOS dates in Eurasia, and the data show a stable trend along the latitudinal gradient. The retrieved SOS dates for boreal forests and tundra ecosystems are most stable in the long term, while in the vegetation areas of low latitudes the dates show higher variability. It is found that from 1982 to 2006, there is a trend of SOS dates becoming earlier for the majority of vegetation types, and the forest coverage areas show even stronger trend of SOS dates becoming earlier, with a change rate of 11.45-15.61 days/25 years, due to global warming. With the exception of the closed to open (>15%) shrubland (<5 m), for most other types of vegetation, there is a negative correlation between vegetation phenology and the average temperature of the month. In other words, for each one degree increase, there is 1.32-3.47 days decrease to SOS date in spring, which is consistent with global warming in recent years.

Key words: climate change, NDVI, phenology, phenology trend, SOS, temperature response