三峡库区土地自然坡度和高程对经济发展的影响

坡度和高程是土地资源固有的二个重要环境因子，对土地利用和土地生产力有直接作用。在山区，坡度和高程基本上决定了土地利用方向和利用方式，从而影响到经济效益和发展潜力。三峡库区面积62640km

IMPACT OF LAND NATURE SLOPE AND SEA LEVEL ELEVATION ON THE ECONOMIC DEVELOPMENT IN THE THREE GORGES' AREA

Nature slope and sea level elevation are two important intrinsicenvironmental factors of land resource which have some direct effects on the use and productive forces of land. In the mountain area, the slope and elevation decide the basical direction and way of landuse, thus influencing on economic benefits and developing potentials. The Three Gorges' area covers 62640 km2 in which mountains are high and slopes steep.The slopes and elevations are separately devided into 4 grades: 0～7°,7～15°,15～25°,＞25° and 2 grades: below 800 m and above 800 m according to the impact levels on agriculture production. We have made the grading map of slope and elevation and the landuse map with remote sensing of the Three Gorges' area, at the 1∶100 000 scale , and at which we have obtained the areas of both land and landuse types of each grade of slopes and elevations. The area of land from grade 1 to 4 increases along with the steep of slope and decreases with the rise of altitude. The fields are mainly distributed on the slopes of 7～15° and 15～25° below 800 m. The forests are mainly distributed on the slopes of over 25°. On the basis of the quantitative analysis and comparison of annual output value of the agriculture of main cities and counties of this area from year 1980 to 1996, it can be seen that there exist clear inverse proportions between the annual output and the nature slope and sea level elevation. For comprehensive enhancent of the productive forces of land, the principle of “there are something to go on doing, something not to go on doing" must be followed, for example ,adjusting the structure of agriculture, not by unilaterally stressing the increase of total yields of grain by expanding the area of land under cultivation, but transforming the middle-low-yield fields with the slopes of 15～25°, returning the dry land with the steep slopes over 25° back to forests or grass step.