论文部分内容阅读
我省西山地区属吕梁山系,是黄土高原的一部分,也是黄河中游侵蚀严重和水土大量流失的地区。包括晋西、晋西北沿黄河一带的28个县,总面积46,200平方公里,占全省总面积的1/3。这一地区森林覆盖率仅7.6％,疏林、灌木、草场又遭不同程度的破坏。侵蚀模数为每平方公里8,000—12,000吨,年输入黄河的泥沙有2.9亿吨,平均每4年流失表土1寸。据化验分析被冲走的每一吨泥沙中含氮0.8—1.5公斤,含磷1.5公斤,含钾20公斤。据这样计算,每年就有625万吨氮磷钾肥被冲走。要想保肥、保土、必先保水,要想保水,必须有植被,植被的作用要能改变小气候,涵养水源,而这个作
Lianshan Mountain in our province is a part of the Loess Plateau and is also a region where severe erosion and large loss of water and soil occur in the middle reaches of the Yellow River. Including west Shanxi, northwest along the Yellow River in 28 counties, with a total area of 46,200 square kilometers, accounting for 1/3 of the total area of the province. The forest coverage in this area is only 7.6%, and the sparse forests, shrubs and pastures have been destroyed to varying degrees. The erosion modulus is 8,000-12,000 tons per square kilometer. There are 290 million tons of sediment input into the Yellow River every year, losing an average of 1 inch of topsoil every four years. According to laboratory analysis, each ton of sediment washed away contains 0.8-1.5 kg of nitrogen, 1.5 kg of phosphorus and 20 kg of potassium. According to this calculation, 6.25 million tons of NPK potash are washed away each year. In order to maintain fertility and preserve soil, we must first keep water. If we want to keep water, we must have vegetation. The role of vegetation should be able to change the microclimate and conserve the water.