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一、森林的荣枯,左右着我区经济的兴衰延安地区,地处陕北黄土高原,北部为丘陵沟壑区,南部为高原沟壑区和部分天然林区。境内有大小河流59条,以洛河、延河、秀延河、汾川河、仕望河较大,径流总量年均10.7亿米~3。有大小山峁6万多个,大小沟道2万多条,水土流失面积占本区总面积70％以上。丘陵沟壑区水土流失更为严重,尤以洛河上游为烈,每公里~2年均侵蚀1.8万多吨。全区年均输入黄河的泥沙总量达2.2亿吨。据测算,流失的泥沙总量中,含氮1.76亿千克,磷3.3亿千克,钾4.4亿千克。我区这种严重的水土流失,并非历来如此。据历史记载,秦汉之前,这里曾是森林茂密、水草丰美、牛羊蕃息的地方。秦筑边墙,明清修茸,每役数十万人,砍树烧砖筑城,长
First, the prosperity of the forest, affecting the economic development of our region Yan’an, is located in northern Shaanxi Loess Plateau, northern hilly and ravine, the southern gully area and part of the natural forest. The territory of the size of the river 59, with Luohe, Yanhe, Sau Yanhe, Fenhe River, Shiwang River larger, total annual runoff of 1.07 billion m ~ 3. There are more than 60,000 large and small mountains, more than 20,000 large and small channels, and the area of soil erosion accounts for more than 70% of the total area of the area. Hilly and gully areas more serious soil erosion, especially in the upper reaches of Luohe is strong, erosion of more than 18,000 tons per kilometer ~ 2 years. The average annual sediment input into the Yellow River reaches 220 million tons. It is estimated that the total amount of sediment loss, containing 176 million kilograms of nitrogen, phosphorus 330 million kilograms, 440 million kilograms of potassium. This area has never been such a serious soil erosion. According to historical records, before the Qin and Han dynasties, where once the lush forests, lush plants, cattle and sheep to rest in peace. Qin built side walls, repair the Ming and Qing dynasties, each serving hundreds of thousands of people, cut trees burning brick city, long