引言 2000年的春天，退耕还林（草）工程在中国启动，这项宏大的生态治理工程涉及数千万农户、投资高达数百亿元，其力度之大，范围之广，在中国历史上可谓史无前例。 　　2000年 3月 9日，国家正式下发了退耕工作实施方案，将长江上游和黄河上中游 13个省区市的 174个县确定为 Introduction In the spring of 2000, the Project of Returning Farmland to Forests (Grassland) was started in China. This magnificent ecological management project involves tens of millions of farmers with an investment of tens of billions of yuan. Its intensity is large and its scope is wide. In the history of China, Can be described as unprecedented. On March 9, 2000, the state formally issued a plan for the implementation of the program of returning farm work to determine 174 counties in the upper reaches of the Yangtze River and the 13 provinces and municipalities in the upper and middle reaches of the Yellow River as