A Conceptual Model for Defining and Assessing Condition of Forest Stands

/ Determining what indicators can be used to measure forest health has been much discussed but largely unresolved in the forestry literature. A model is presented in which the condition of a stand is quantified relative to a suitable target condition based on a preselected set of stands that, in the opinions of the managers, meet management objectives. Each stand was characterized by a list of variables that were selected from the existing forest database. We termed these characterizations stand profiles. Profiles of inventory data for 28 stands, each managed for either wildlife habitat or timber production in the Wallowa-Whitman National Forest in eastern Oregon, USA, were used to develop this model. Healthy stands were represented by points in multidimensional scaling space that fell within the bounds of a 65% kernel density estimation of the distribution of stands preselected for each management objective. Stands falling outside these bounds were, by definition unhealthy, and the distance from the bounds is a measure of degree of unhealthiness. Operationally, the objectives of silvicultural manipulations would be to maintain or move points to within the target space by selectively manipulating the values composing stand profiles. The direction and length of the trajectory associated with manipulations is an indicator of the effect of management actions. More work needs to be done to develop and validate this method. KEY WORDS: Monitoring forest condition; Forest health; Decision making; Silviculture prescriptions; Forest management; Forest pests; Forest diseases; Forest insects