2001-2010年秦岭森林物候时空变化遥感监测

植被物候是陆地生态系统对全球气候变化响应的最佳指示器,研究其时空变化对深入理解陆面水热过程、碳循环过程及预测陆地生态系统的时空变化具有重要意义。本文采用2001-2010年MODIS MOD09A1产品,通过引入MOD09A1的时间控制层DOY(Day of Year)提高EVI的时间精度;采用最大变化速率法和阈值法相结合提取秦岭森林物候期。结果表明,随着水热条件变化,由低海拔至高海拔,东南向西北,生长季始期(Start of Growth Season, SOG)逐渐推迟,集中在第81~120 d(即从3月下旬-4月末);生长季末期(End of Growth Season, EOG)逐渐提前,集中在第270~311 d(10月初-11月上旬);生长季长度(Length of Growth Season, LOG)逐渐缩短,集中在150~230 d。秦岭森林物候期与海拔关系密切,海拔每升高100 m,SOG推迟2 d,EOG提前1.9 d,LOG缩短3.9 d。2001-2010年,森林SOG提前、EOG延后和LOG延长主要分布于秦岭中高海拔区;SOG延后、EOG提前和LOG缩短主要分布在海拔1000 m以下部分区域。高海拔区物候的年际变化要比低海拔区复杂,2000 m以上区域SOG提前、EOG提前、LOG缩短。上述研究结果量化了不同海拔梯度森林的物候差异,揭示了近10年秦岭森林物候的时空格局,可为秦岭地区生态环境评价和保护提供科学依据。

Spatiotemporal variations of forest phenology in the Qinling zone based on remote sensing monitoring, 2001-2010

Plant phenology is one of the most salient and sensitive indicators of terrestrial ecosystem's response to climate change. Understanding its spatiotemporal change is significantly important for understanding both land surface processes and carbon cycle and predicting changes in the terrestrial ecosystem. MODIS MOD09A1, with the spatial resolution of 500 m × 500 m and at an 8-day temporal interval, was used in this study to investigate the change in forest phenology in the Qinling zone of central China in 2001?2010. First, we used the day of year (DOY) of MOD09A1 to improve the temporal precision of EVI; we then combined the maximum ratio and the threshold method for phenology data extraction start of growth season (SOG), end of growth season (EOG), and length of growth season (LOG)] in the Qinling zone. Results of this study show that: Accompanying the deterioration in heat and water conditions from low altitude to high altitude and southeast to northwest, SOG delayed, EOG advanced, and LOG shortened gradually. SOG and EOG mainly occurred on the 81th?120th and 270th?311th days respectively. LOG was mainly between 150 and 230 days. The phenology of forest in Qinling zone is closely related to altitude, with every 100 m rising in altitude, SOG, EOG, and LOG gradualy delayed 2 days, advanced 1.9 days, and shortened 3.9 days, respectively. From 2001 to 2010, early SOG, late EOG, and extended LOG mainly occurred in medium altitude. SOG, EOG, and LOG gradually delayed, advanced, and shortened respectively in some areas that are lowered than 1,000 m above sea level. Interannual changes at high altitude were more complicated than that at low altitude, and SOG advanced, EOG advanced, and LOG shortened above 2000 m. The reasons for these changes remain unclear. The findings quantified the differences of forest phenology with the change in elevation and revealed the spatiotemporal variations in forest phenology from 2001 to 2010. This article provides a reference for the evaluation and protection of ecological environment in the Qinling zone. In future study, reasons for the above mentioned differences in forest phenology need to be explored.