在日本,为了满足各种管理目的而建立的防护林林种有17个,其总面积1980年大约为714万公顷,其中约75%(或者说约514万公顷),是遍布全国水源地的水源涵养林,从这个统计数字就可以看出,水源涵养林在17个防护林林种中占有非常重要的地位.森林对水的作用问题包括三个方面—水质、水量和洪峰流量的调节.对于这三方面的问题很多学者曾发表过许多著作予 In Japan, there are 17 shelterbelts established to meet various management purposes. The total area is about 7.14 million hectares in 1980, of which about 75% (or about 5.14 million hectares) is a source of water all over the country According to this statistics, water conservation forests play a very important role in the development of 17 shelterbelts, and the role of forests in water issues includes three aspects: water quality, water quantity and peak flow regulation. Three Issues Many scholars have published many books