1990—2020年三峡库区植被物候时空格局及其演变机制

Spatio⁃temporal patterns of vegetation phenology and their evolutionary mechanisms in the Three Gorges Reservoir Area from 1990 to 2020

作为长江上游生态屏障的核心区,三峡库区特殊的地理位置使其在推动长江经济带发展和生态文明建设中肩负着重大使命。三峡库区的生态环境在蓄水前后发生了较大改变,其变化能通过植被物候的变动体现,研究三峡库区植被物候时空演变特征及其驱动力,对于区域生态可持续发展和长江经济带生态文明建设具有重要意义。借助动态阈值法提取物候参数,整合多源遥感物候参数提取结果,分析1990—2020年三峡库区植被物候时空格局;结合Theil-Sen Median趋势分析与Mann-Kendall检验等方法,定量分析三峡库区蓄水前后植被物候时空演变特征;运用地理加权回归分析、Pearson相关性分析以及主成分分析等方法,定量探究三峡库区植被物候时空演变的影响因素。结果表明:(1)近31年来,三峡库区植被的生长季开始时间(Start of Growing Season,SOS)主要出现在60 DOY(Date of Year),生长季结束时间(End of Growing Season,EOS)主要出现在301 DOY,生长季长度(Length of Growing Season,LOS)总体为248 d。在空间上,SOS与EOS均呈现出从库首至库尾逐渐提前的趋势,LOS的空间异质性较小。(2)库区植被物候表现出SOS提前、EOS推迟和LOS延长的特征,SOS提前的平均幅度为0.3 d/a,库首区域最为典型;EOS推迟的平均幅度为0.8 d/a,库尾区域尤为明显;LOS延长的平均幅度为1.7 d/a,库尾区域更加突出。植被物候对库区蓄水的响应表现出一定的滞后性。(3)人为因素与间接人为因素(水位、人口和水域面积等)是影响库区植被物候时空分异的主要因素。

As the core area of the ecological barrier in the upper reaches of the Yangtze River,the Three Gorges Reservoir Area(TGRA),due to its special geographical location,has a major role to promote the development of the Yangtze River Economic Belt and the construction of ecological civilization.The ecological environment of the TGRA has altered significantly before and after the impounding of the reservoir,which may be a reflection of the change in vegetation phenology.Therefore,it is of great significance to study the spatial and temporal evolutionary characteristics of vegetation phenology and its driving forces in the TGRA for sustainable development of regional ecology and the construction of ecological civilization in the Yangtze River Economic Belt.The study analyzed the spatial and temporal patterns of vegetation phenology in the TGRA from 1990 to 2020 by integrating the results of multi⁃source remote sensing phenological parameter extraction using the dynamic threshold method.Combined with Theil⁃Sen Median trend analysis and Mann⁃Kendall test,the temporal and spatial evolution characteristics of vegetation phenology before and after the impounding of the reservoir were quantitatively analyzed.Geographic weighted regression analysis,Pearson correlation analysis and principal component analysis were used to quantitatively explore the factors influencing the spatio⁃temporal evolution of vegetation phenology in the TGRA.The results showed that:(1)over the past 31 years,the Start of Growing Season(SOS)of vegetation in the TGRA mainly occurred at 60 DOY(Date of Year),the End of Growing Season(EOS)mainly occurred at 301 DOY,and the Length of Growing Season(LOS)was 248 days.Spatially,both SOS and EOS showed a trend of gradually advancing from the head to the tail of the reservoir,and the spatial heterogeneity of the LOS was smaller.(2)The vegetation phenology showed the characteristics of SOS advance,EOS delay,and LOS prolongation.The average amplitude of SOS advance was 0.3 d/a,which was particularly evident at the head of the reservoir.The average amplitude of EOS delay was 0.8 d/a,which was particularly evident at the tail of the reservoir.The average amplitude of LOS prolongation was 1.7 d/a,which was particularly evident at the tail of the reservoir.The response of vegetation phenological to reservoir water storage showed a certain time lag.(3)Anthropogenic factors and indirect anthropogenic factors,including water level,population,and water area were main factors influencing the spatial and temporal variability of vegetation phenology in TGRA.