基于EVI2和多趋势分析法的高原草地植被物候动态监测研究

基于EVI2数据集提取青藏高原草地植被的物候信息,分析青藏高原草地返青期(Start of Growth Season,SOG)、枯黄期(End of Growth Season,EOG)和生长季长度(Length of Growth Season,LOG)的空间分布格局及近30 a来青藏高原草地物候的时空动态变化特征。结果表明:青藏高原的草地物候由东南向西北呈现出明显的区域性差异。其中,高原东部和西北部地区的草地植被返青时间早于中部和西南部地区,而枯黄时间却晚于中部和西南部地区,生长季长度较中部和西南部地区长。同时,青藏高原物候变化趋势在东西部地区的差异十分明显。草地植被返青提前的区域主要集中在高原的东部,提前速率为0.49 d/a(R^2=0.54)。草地植被物候分布和变化趋势在不同海拔和坡向上的差异也十分显著。海拔每升高1 000 m,草地SOG推迟4 d,EOG提前5 d,LOG缩短9 d。随海拔的升高,草地SOG的推迟速率逐渐增加,LOG变化速率呈现出逐渐减小的趋势。此外,南坡草地SOG较北坡晚,其LOG较北坡、东坡和西坡的短。北坡草地SOG平均推迟速率低于南坡。

Dynamic Monitoring of Grassland Vegetation Phenology in Tibetan Plateau based on EVI2 and Three Trend Approaches

Based on grassland vegetation phenology extracting from EVI2 data sets,distribution and dynamic variation characteristic of SOG,EOG and LOG were analyzed in recent 30 years.The results showed that grassland phenology had shown an obvious regional difference from southeast to northwest in TP.The grassland vegetation in eastern and northwestern part of plateau turned green earlier and brown late,with a relatively longer growth season than other regions.The changes of grassland vegetation phenology from 1981 to 2010 in the east and west regions were also remarkable in TP.The Start of Growth Season(SOG)was in advance in eastern region,with the advanced rate of 0.49 d/a(R^2=0.54).There were remarkable difference in phenology distribution and changes in different elevations and aspects.When the altitude had risen 1000 m,the SOG delayed 4 days,EOG advanced 5 days,and LOG shorten 9 days.With the increase of altitude,the SOG rate of grassland increased gradually,and LOG change rate showed a decreasing trend.In addition,SOG in south aspect was later than that in north aspect.LOG in south aspect was shorten than that in others.Average delay rate of SOG in north aspect was lower than that in south aspect.