土地覆被对黄河中游流域泥沙产生的影响

本在黄河中游地区选择了近60个水测站流域，流域面积从500～2500km^2，分别代表6种不同自然地理类型。运用遥感方法和专题地图，结合野外实地调查，在流域泥沙及植被、地面物质等数据采集的基础上，利用数理统计方法，建立了流域产沙量与植被、地面物质之间的定量关系。结果表明，植被和地面物质对流域产沙量有着十分重要的影响。流域产沙量与植被之间呈现相当好的非线性负相关关系，而与地面物质呈明显的线性正相关关系。流域产沙量随植被变化存在着二个临界值，一是当流域植被覆盖度等于30％时，另一是当植被覆盖度等于70％时。这一现象以往只是在试验小区或试验流域见到，而本的研究表明，类似的现象在天然河流流域也存在。多元回归表明，在影响流域产沙量诸因素中，植被的影响是最重要的，其次是地面物质。

Effect of land cover on sediment yield in the middle Yellow River basin

More than 50 river basins were chosen for analysing the relationships between sediment yield and land cover in the middle Yellow River They have drainage areas ranging from 500 to 2500 km 2 and come from 7 types of physiographical environments A set of data on sediment yield and surface material, vegetation cover and basin morphological features were collected by using remote sensing and thematic maps combined with field check and indoor analysis Based on this a correlative analysis was made between sediment yield and surface material and vegetation cover It was shown that good positive linear relationships exist between sediment yield and surface material but non linear negative relationship exists between sediment yield and vegetation cover Different positions can be identified in Figs 1 and 2 for those river basins from wide range of physiographical environments as surface materials of river basins change from sandy loess and highly weathered silt mudstone through loess rock mixture to hard rock and vegetation coverage increase Two thresholds can be observed as sediment yield changes with vegetation coverage, where vegetation coverage is equal to 30% and 70% respectively It is interesting that this phenomenon could be seen before only in experimental plots and watershed, but this paper proved that similar relations exist in natural river basins It was shown by multiple regressions that the most important factor affecting sediment yield is vegetation cover, followed by surface material