6Alexander S A, Palmert C J. Forest health monitoring in the United States : First four years [ J ]. Environment monitor assess, 1999, 55 (2): 267-277.
7Blather K A, Keegan C A, O Lau gin, Adams D L. Forest health management policy: A case study in southwestern in alto [G]. In: Sampson R N ad. Assessing forest ecosystem health in the land west. New York: Food Products Press, 1993: 317 -318.
8Callicott J B. Aldo Leopold'metaphor [ G ]. Ecosystem Health: New Goals for Environmental Management, Washington: Island Press, 1992 : 42 - 56.
9Callicott J B. Aldo and the foundations of enosis-tem management [J]. Journal Forest, 2000 (5) : 5 - 13.
10Leopold J C. Getting a handle on ecosystem health [J]. Science, 1997:276 -287.
