The incision of the Sanmen Gorge marks the birth of the modern Yellow River,but its timing varies from the late Miocene-early Pliocene to the late Pleistocene(~0.15 Ma),and the suggested forcing mechanisms vary from t...The incision of the Sanmen Gorge marks the birth of the modern Yellow River,but its timing varies from the late Miocene-early Pliocene to the late Pleistocene(~0.15 Ma),and the suggested forcing mechanisms vary from the uplift of the Tibetan Plateau to global climate change.Here,we report sedimentologic,geochronologic,and provenance data from a drill core near the Sanmen Gorge,the last gorge along the main course of the Yellow River.Our results indicate that typical river channel deposits,with detritus from the Ordos Block in the upstream regions,started to accumulate in the Sanmen Gorge at~1.25 Ma.When integrated with river terrace evidence from the upstream and downstream regions,the results provide robust evidence that the final integration of the modern Yellow River occurred at~1.25 Ma,consistent with the beginning of the Mid-Pleistocene transition(MPT).We propose that the accelerated lowering of eustatic sea level during the MPT may play as important a role as tectonism in driving the birth and evolution of the modern Yellow River.展开更多
选取长江上游地区生态环境相对脆弱的宜宾市为典型案例,分析其16年来NDVI所表征的植被生长动态变化。以MODIS MOD 13Q1为数据源,采用Sen+Manna-Kendall非参数检验方法和Hurst指数模型,分析NDVI时间变化特征、变化趋势与未来可持续特征,...选取长江上游地区生态环境相对脆弱的宜宾市为典型案例,分析其16年来NDVI所表征的植被生长动态变化。以MODIS MOD 13Q1为数据源,采用Sen+Manna-Kendall非参数检验方法和Hurst指数模型,分析NDVI时间变化特征、变化趋势与未来可持续特征,并应用空间转移矩阵和重心迁移模型分析其空间变化特征,最后应用地理探测器模型探测影响NDVI空间分布的主导因素,进一步揭示NDVI分异特征及其驱动力。结果表明:(1)2000—2015年宜宾市植被覆盖整体状况良好,自北向南逐渐优化,多年平均NDVI大于0.6的区域占52.06%。年际NDVI以极显著趋势波动增长,平均年际变化率达到0.007/a,极显著增长区域面积达70.18%。与此同时,NDVI增长整体持续性不强,未来可能出现波动的区域占53.65%。(2)2000—2015年间宜宾市植被生长以正向演进为主,演进过程和已有生态建设工程成效研究结论相符,生态环境不断优化。(3)宜宾市NDVI主要受一系列地表差异,包括海拔、年均温、土地利用类型、人口密度所决定,其因子解释力均超过25%,自然环境因素与人类活动共同作用对NDVI影响更加显著。展开更多
基金supported by the Fundamental Research Funds for the Central Universities,China(lzujbky-2021-ey12)the National Natural Science Foundation of China(42072211)+1 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(2019QZKK0602)the National Non-Profit Fundamental Research Grant of China(IGCEA 2008)。
文摘The incision of the Sanmen Gorge marks the birth of the modern Yellow River,but its timing varies from the late Miocene-early Pliocene to the late Pleistocene(~0.15 Ma),and the suggested forcing mechanisms vary from the uplift of the Tibetan Plateau to global climate change.Here,we report sedimentologic,geochronologic,and provenance data from a drill core near the Sanmen Gorge,the last gorge along the main course of the Yellow River.Our results indicate that typical river channel deposits,with detritus from the Ordos Block in the upstream regions,started to accumulate in the Sanmen Gorge at~1.25 Ma.When integrated with river terrace evidence from the upstream and downstream regions,the results provide robust evidence that the final integration of the modern Yellow River occurred at~1.25 Ma,consistent with the beginning of the Mid-Pleistocene transition(MPT).We propose that the accelerated lowering of eustatic sea level during the MPT may play as important a role as tectonism in driving the birth and evolution of the modern Yellow River.
文摘选取长江上游地区生态环境相对脆弱的宜宾市为典型案例,分析其16年来NDVI所表征的植被生长动态变化。以MODIS MOD 13Q1为数据源,采用Sen+Manna-Kendall非参数检验方法和Hurst指数模型,分析NDVI时间变化特征、变化趋势与未来可持续特征,并应用空间转移矩阵和重心迁移模型分析其空间变化特征,最后应用地理探测器模型探测影响NDVI空间分布的主导因素,进一步揭示NDVI分异特征及其驱动力。结果表明:(1)2000—2015年宜宾市植被覆盖整体状况良好,自北向南逐渐优化,多年平均NDVI大于0.6的区域占52.06%。年际NDVI以极显著趋势波动增长,平均年际变化率达到0.007/a,极显著增长区域面积达70.18%。与此同时,NDVI增长整体持续性不强,未来可能出现波动的区域占53.65%。(2)2000—2015年间宜宾市植被生长以正向演进为主,演进过程和已有生态建设工程成效研究结论相符,生态环境不断优化。(3)宜宾市NDVI主要受一系列地表差异,包括海拔、年均温、土地利用类型、人口密度所决定,其因子解释力均超过25%,自然环境因素与人类活动共同作用对NDVI影响更加显著。
