单 位：
北京市园林绿化局;北京林业大学水土保持与荒漠化防治教育部重点实验室
关键词：
黄河中游;河龙区间;植被恢复;退耕还林;径流输沙
摘 要：
黄河中游河口镇至龙门区间(河龙区间)是黄河主要的多沙粗沙区,黄河泥沙主要来源于此。为揭示近10年退耕还林工程实施以来河龙区间植被覆盖恢复过程及其对河龙区间径流输沙的影响,该文基于GIMMS和SPOTVGT两种遥感数据,采用GIS空间分析方法研究了1981-2007年河龙区间植被覆盖时空变化及其与径流输沙的关系。研究发现:1981-2003年河龙区间归一化植被指数(normal difference vegetationindex,NDVI)整体呈上升趋势,位于其西北部地势平坦的沙地草滩区植被NDVI上升趋势显著,而黄土丘陵沟壑区和山地森林区的植被NDVI呈下降趋势。②退耕还林工程实施以来,1999-2007年河龙区间植被NDVI在降水偏低的背景下,仍表现出显著的上升趋势,植被覆盖恢复同势强劲。植被NDVI上升最显著区域位于黄土丘陵沟壑区,即窟野河、秃尾河、无定河中下游以及延河中下游地区。从前后两个时期对比看,后期NDVI较前期提高10%以上和20%以上的区域分别占总面积的72.5%和36.4%。③1950-2007年河龙区间产流量、产沙量呈减少趋势,尤其自20世纪80年代以来,减少趋势非常明显。与1950-1969年相比,1980-2007年产流量和产沙量分别减少了34.8×108m3和6.4×108t,占前期的49.4%和64.9%。④河龙区间植被NDVI与产流量、产沙量存在正相关关系,但退耕还林工程实施后,这种同步波动关系发生扭转,表现为植被NDVI上升,产流量、产沙量下降。虽然降水偏少是河龙区间产流、产沙下降的重要原因,但植被恢复可能加剧了该趋势。
译 名：
Vegetation restoration and its effects on runoff and sediment yield in Hekouzhen-Longmen Section of the middle reaches of Yellow River
作 者：
XIN Zhong-bao1;YU Xin-xiao1;GAN Jing2;WANG Xiao-ping2;LI Jin-hai2.1 Key Laboratory of Soil and Water Conservation & Desertification Combating of Ministry of Education,Beijing Forestry University,100083,P.R.China;2 Beijing Municipal Bureau of Landscape and Forestry,100029,P.R.China
关键词：
middle reaches of Yellow River;Hekouzhen-Longmen Section;vegetation restoration;conversion of cropland to forestland;runoff and sediment
摘 要：
Sediment yield of the Yellow River is mainly originated from the drainage area between Hekouzhen and Longmen area(Helong Section).Spatio-temporal variations of vegetation cover in this area during 1981--2007 were investigated using GIMMS and SPOT VGT NDVI data.The authors also analyzed the interannual variations of vegetation cover,annual runoff and sediment yield,which were resulted from precipitation changes and the Project of Conversion of Cropland to Forestland(PCCF).The results showed that vegetation cover of Helong area had experienced an increasing trend during 1981--2007.The northwestern Helong,where the flat sandy land was covered by grass,was the mostly significant increasing region.The region where vegetation cover showing a decreasing trend mainly appeared in southern and southeastern Helong area,which was gullied hilly area or forested area.During 1999--2007,although precipitation was relatively low,vegetation cover showed a significant increasing trend in the Helong area due to the implementation of PCCF.During 1999--2007,the most significant improvement of vegetation cover mainly appeared on the loess gullied hilly area,such as the drainage basins of the Kuye River,Tuwei River and the middle and lower reaches of Wuding River and Yanhe River.Comparison of the average annual maximum NDVI between the earlier(1998--2002)stage and the later stage(2003--2007)of PCCF indicated that,the areas with increases of 10% and 20% in NDVI accounted for 72.5% and 36.4% of the total area,respectively.Interannual variability of annual runoff and sediment yield showed a decreasing trend,especially since the 1980s,the decreasing trend was very obvious.Compared with 1950--1969,the average runoff and sediment yield of 1980--2007 decreased by 34.8×108 m3 and 6.4×108 t,accounting for 49.4% and 64.9% to those of 1950--1969,respectively.There was a positive correlation between the annual maximum NDVI and annual runoff as well as sediment yield.But the positive correlation had been reversed after the implementation of PCCF since 1999,i.e.an increasing NDVI trend of the Helong area was associated with the decreased runoff and sediment yield.Although less precipitation was an important driving factor for the decreasing runoff and sediment yield during 1999--2007,the restoration and improvement of vegetation cover might exacerbate this decreasing trend by enhancing evapotranspiration and alleviating soil erosion.
