1982-2006 年欧亚大陆植被生长季开始时间遥感监测分析

植被物候是环境条件季节和年际变化最直观、最敏感的生物指示器,物候变化可以反映陆地生态系统对气候变化的快速响应.论文基于1982-2006 年连续25 年的GIMMS AVHRR NDVI数据,采用动态阈值法、延迟滑动平均法,双Logistic 和Savitzky-Golay 方法提取欧亚大陆植被的生长季开始时间,并对不同方法的提取结果进行比较和分析.然后以动态阈值法的物候提取结果,研究了1982-2006 年期间植被物候变化趋势以及物候对温度变化的响应情况.结果表明：动态阈值法在欧亚大陆地区生长季开始时间提取率高,在纬度上的变化趋势稳定;北方森林/针叶林和苔原地区的生长季开始时间提取结果最稳定,低纬度区域的变率最大.1982-2006 年,大部分植被类型的生长季开始时间表现出提早趋势,其中森林覆盖区域提早趋势明显,变化幅度为11.45~15.61 d/25a;除了郁闭式至开放式( > 15%) 灌木丛( < 5 m)植被类型外,植被物候和温度表现出负相关关系,变化幅度为1.32~3.47d/℃,这也验证了近几十年气候变暖的趋势.

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

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.