Sediment discharge from the Yellow River originates mainly from the drainage area between Hekouzhen and Longmen, i.e., the Helong area. Spatial-temporal variations of the vegetation cover in this area during the 1981-...Sediment discharge from the Yellow River originates mainly from the drainage area between Hekouzhen and Longmen, i.e., the Helong area. Spatial-temporal variations of the vegetation cover in this area during the 1981-2007 period have been investigated using GIMMS and SPOT VGT NDVI data. We have also analyzed the interannual variations in vegetation cover and changes in annual runoff and sediment discharge, the consequences from precipitation change and the Grain for Green Project （GGP）. The results show that vegetation cover of the Helong area has increased during the 1981-2007 period. The northwestern part the Helong area, where the flat sandy lands are covered by grass, has experienced the largest increase. The region where the vegetation cover has declined is largely found in the southern and southeastern Helong area, which is a gullied hilly area or forested. Although precipitation was relatively low during the 1999-2007 period, the vegetation cover showed a significant increase in the Helong area, due to the implementation of the GGP. During this period, the most significant improvement in the vegetation cover occurred mainly in the gullied hilly areas of the Loess Plateau, such as the drainage basins of the Kuyehe and Tuweihe rivers and the middle and lower reaches of the Wudinghe and Yanhe rivers. A comparison of the average annual maximum NDVI between the earlier （1998-2002） stage and the next five years （2003-2007） of the GGP indicates that the areas with increases of 10% and 20% in NDVI account for 72.5% and 36.4% of the total area, respectively. Interannual variation of annual runoff and sediment discharge shows a declining trend, especially since the 1980s, when the decrease became very obvious. Compared with the 1950-1969 period, the average runoff during the 1980-2007 period was reduced by 34.8 × 10^8 m3 and the sediment discharge by 6.4 ×10^8 t, accounting for 49.4% and 64.9% of that in the 1950-1969 period, respectively. There is a positive correlation between the annual maximum NDVI展开更多
黄河中游河龙区间是我国退耕还林/还草工程(Grain for Green Project,GGP)实施的重点区和典型区,定量评估该流域植被动态及其对径流的影响,对流域水资源可持续利用以及GGP工程的生态水文效应评价具有重要意义。该研究基于遥感、GIS技术...黄河中游河龙区间是我国退耕还林/还草工程(Grain for Green Project,GGP)实施的重点区和典型区,定量评估该流域植被动态及其对径流的影响,对流域水资源可持续利用以及GGP工程的生态水文效应评价具有重要意义。该研究基于遥感、GIS技术、数理统计和布迪克弹性系数法,利用7期植被类型数据,定量评估了37年来河龙区间植被覆盖的时空变化格局及其对径流变化的影响。结果表明:(1)植被变化并未显著地改变河龙区间各植被类型的时空分布格局;(2)GGP的实施改变了各植被类型的平衡状态和转化速度;(3)植被变化是GGP实施后10年(2000-2010年)径流下降的主要驱动因素,但随后降水的持续增加,使得植被的"减水效应"趋于缓和。展开更多
基金supported by Beijing Forestry University for Young Scientist and funded by the National Natural Science Foundation of China (Grant No.40871136)
文摘Sediment discharge from the Yellow River originates mainly from the drainage area between Hekouzhen and Longmen, i.e., the Helong area. Spatial-temporal variations of the vegetation cover in this area during the 1981-2007 period have been investigated using GIMMS and SPOT VGT NDVI data. We have also analyzed the interannual variations in vegetation cover and changes in annual runoff and sediment discharge, the consequences from precipitation change and the Grain for Green Project （GGP）. The results show that vegetation cover of the Helong area has increased during the 1981-2007 period. The northwestern part the Helong area, where the flat sandy lands are covered by grass, has experienced the largest increase. The region where the vegetation cover has declined is largely found in the southern and southeastern Helong area, which is a gullied hilly area or forested. Although precipitation was relatively low during the 1999-2007 period, the vegetation cover showed a significant increase in the Helong area, due to the implementation of the GGP. During this period, the most significant improvement in the vegetation cover occurred mainly in the gullied hilly areas of the Loess Plateau, such as the drainage basins of the Kuyehe and Tuweihe rivers and the middle and lower reaches of the Wudinghe and Yanhe rivers. A comparison of the average annual maximum NDVI between the earlier （1998-2002） stage and the next five years （2003-2007） of the GGP indicates that the areas with increases of 10% and 20% in NDVI account for 72.5% and 36.4% of the total area, respectively. Interannual variation of annual runoff and sediment discharge shows a declining trend, especially since the 1980s, when the decrease became very obvious. Compared with the 1950-1969 period, the average runoff during the 1980-2007 period was reduced by 34.8 × 10^8 m3 and the sediment discharge by 6.4 ×10^8 t, accounting for 49.4% and 64.9% of that in the 1950-1969 period, respectively. There is a positive correlation between the annual maximum NDVI
文摘黄河中游河龙区间是我国退耕还林/还草工程(Grain for Green Project,GGP)实施的重点区和典型区,定量评估该流域植被动态及其对径流的影响,对流域水资源可持续利用以及GGP工程的生态水文效应评价具有重要意义。该研究基于遥感、GIS技术、数理统计和布迪克弹性系数法,利用7期植被类型数据,定量评估了37年来河龙区间植被覆盖的时空变化格局及其对径流变化的影响。结果表明:(1)植被变化并未显著地改变河龙区间各植被类型的时空分布格局;(2)GGP的实施改变了各植被类型的平衡状态和转化速度;(3)植被变化是GGP实施后10年(2000-2010年)径流下降的主要驱动因素,但随后降水的持续增加,使得植被的"减水效应"趋于缓和。
