黄河下游宽滩区及其沿线植被覆盖度变化特征

Study on the Variation Characteristics of Vegetation Coverage Along the Lower Yellow River Floodplain

植被覆盖度是反映黄河下游宽滩区生态环境状态的重要指标,其变化反映了自然演化和人类活动对生态环境的影响,以黄河下游宽滩区及其沿线行政区为研究对象,利用1987年、1994年、1998年、2003年、2008年、2013年、2017年Landsat遥感影像,采用归一化植被指数像元二分法,反演出植被覆盖度及其分级,利用一元线性趋势分析、转移矩阵法、重心迁移模型、相关性分析等方法,探究研究区植被覆盖度时空变化特征及影响因素。结果表明:黄河下游宽滩区沿线及宽滩区内植被覆盖整体呈改善趋势,且宽滩区内植被覆盖度在2003年之后与宽滩区沿线植被覆盖度差距逐渐减小并在2017年实现反超;黄河下游宽滩区沿线植被覆盖度年内变化呈现明显“双峰型”特征;河道收束和城镇化发展对植被覆盖度年际变化有重要影响。

Vegetation coverage is an important indicator to reflect the ecological environment status of the lower Yellow River floodplain and its changes mirror natural evolution and the effect of human activities on the ecological environment.The county-level administrative area involved in the wide beach area of the lower Yellow River was used as the research area,and the seven periods of Landsat in 1987,1994,1998,2003,2008,2013 and 2017 were used as the remote sensing data source.It used the pixel dichotomy method based on the NDVI index to obtain vegetation coverage and classification.It used the methods of univariate linear trend analysis,transfer matrix method,center of gravity transfer model and correlation analysis to analyze the spatial and temporal changes of vegetation coverage in the study area and the influencing factors.The results show that the overall vegetation coverage in the broad beach area of the lower Yellow River and along the area has shown an overall improvement trend in the past 30 years.The gap between the vegetation coverage in the beach area and the vegetation coverage in the coastal administrative areas are gradually decreased after 2003,and it achieves an overtake in 2017.The annual change of vegetation coverage presents an obvious“bimodal”characteristic.The channel contraction and the development of urbanization have an important impact on the inter-annual changes in vegetation coverage.