美国国家公园系统保护区规模的变化特征及其原因分析

美国国家公园系统的保护区其规模具有随保护区类型、建设时间和地区分布的不同而变化的特征。自然保护思想和保护区建设中土地的可获得性是形成上述特征的主要因素。其中自然保护思想对保护区规模大小有指导作用，而土地的可获得性则直接影响保护区面积。

The Reserve Area of the National Park System in the United States, Its Scale Variation and Affection Factors

The reserve area of the National Park System in the United States varies with the catopries, time of establishment, and the distribution of reserves. The main factors afforting the variation are the idea of conservation and the mpibility to acquire land for reserves. The conservation idea provides directive function for the reserve area. The possibility of land acquiring affect the reserve area itnmediately.