黄河流域2001—2020年植被物候及其对气候变化的响应

Vegetation phenology and its response to climate change in the Yellow River Basin from 2001 to 2020

植被周期性的物候更替被公认为是全球气候变化的综合指示器,深入研究区域植被物候的变化趋势和时空特征,可以提高对该区生态系统稳定性及动态变化程度的认识。基于2001—2020年16天、250m分辨率的中分辨率成像光谱仪归一化植被指数(MODIS NDVI)数据,利用Savitzky-Golay滤波法(S-G)和相对阈值法提取黄河流域植被物候参数,结合谷歌地球引擎(GEE)平台提供的欧洲中期天气预报中心第五代陆地再分析数据集(ERA5-LAND)小时气候再分析数据集和气候危害组红外降水站数据(CHIRPS)日降水数据集数据,运用趋势分析和偏相关分析等方法,探究全球气候变化下黄河流域不同植被分区物候参数空间分布特征、变化趋势,及其对气候因子的响应。结果表明:(1)2001—2020年黄河流域气候整体呈暖湿化的发展趋势,年均温上升幅度为0.15℃/10a(P>0.05),年降水增加幅度为24mm/10a(P<0.05)。(2)黄河流域暖温带落叶阔叶林区域的生长季始期和中期最早,温带南部典型草原亚地带和温带南部荒漠草原亚地带最晚,温带灌木、禾草半荒漠亚地带的生长季结束期最晚,青藏高原高寒植被区域的生长季长度最短。(3)全流域内生长季始期和中期分别有69.3%和66.4%的面积呈提前趋势(P<0.05),生长季末期50.9%的面积结束期呈推迟趋势(P<0.05),66.1%的面积整个生长季长度呈延长趋势(P<0.05)。(4)不同植被地带气候对物候参数影响存在差异,温度因子对带北部典型草原亚地带、高寒草原地带和高寒草甸地带的物候参数影响较大,降水和太阳辐射因子对温带南部典型草原亚地带、温带灌木、禾草半荒漠地带、温带南部荒漠草原亚地带和中亚热带常绿阔叶林地带的物候参数影响较大。

Vegetation phenology is widely recognized as a comprehensive indicator of global climate change.Studying the spatiotemporal characteristics and trends of regional vegetation phenology can improve our understanding of the stability and dynamic changes of the ecosystem.Based on the 16day,250m resolution MODIS NDVI data from 2001 to 2020,this study used the S-G filtering method and the relative threshold method to extract vegetation phenology parameters in the Yellow River Basin.Combined with the ERA5-LAND hourly climate reanalysis dataset and CHIRPS daily precipitation dataset provided by GEE platform,using trend analysis and partial correlation analysis methods,we explored the spatial distribution characteristics and change trends of vegetation phenology in different vegetation zones under global climate change.We also analyzed its response to climate factors.The results show that:(1)the climate in the Yellow River Basin presented a warm and humid development trend from 2001 to 2020,with an annually average temperature increase of 0.15℃/10a(P>0.05)and an annual precipitation increase of 24mm/10a(P<0.05).(2)The warm temperate deciduous broad-leaved forest region in the Yellow River Basin had the earliest start of the growing season and middle time of the season,while the typical grassland subzone in the southern temperate zone and the desert grassland subzone in the southern temperate zone had the latest start of the growing season and middle time of the season.The end of the growing season in the temperate shrub-grass semi-desert zone was the latest,and the length of growing season in the alpine vegetation region on the Qinghai-Tibet Plateau was the shortest.(3)Within the whole basin,69.3%and 66.4%of the area showed an advance trend(P<0.05)for start of the growing season and middle time of the season,respectively,50.9%of the area showed a delay trend(P<0.05)for end of the growing season,and 66.1%of the area showed an extension trend(P<0.05)for length of growing season.(4)There were differences in climate impacts on phenology parameters among different vegetation zones.Temperature had a greater impact on phenology parameters in typical grassland subzone in northern temperate zone,alpine grassland zone,and alpine meadow zone,while precipitation and solar radiation factors had a greater impact on phenology parameters in typical grassland subzone in southern temperate zone,temperate shrub-grass semi-desert zone,desert grassland subzone in southern temperate zone and mid-subtropical evergreen broad-leaved forest zone.