自二十世纪八十年代中期以来,美国林业科研的重要部门就已经进行大气污染物对森林生态系统影响的研究(Schroeder和Keister,1989)。该研究旨在确定各种污染物对美国不同的森林生态系统所造成的损失数量,从而为政策分析提供情报。目前用于估测森林损害的两种基本方法是野外调查与对照试验。野外调查是使用从量测 Since the mid-1980s, major sectors of forestry research in the United States have studied the impact of air pollutants on forest ecosystems (Schroeder and Keister, 1989). The study aimed to determine the amount of damage caused by various pollutants to different forest ecosystems in the United States, thus providing intelligence for policy analysis. The two basic methods currently used to estimate forest damage are field surveys and controlled trials. Field surveys are used from the measurement