Site Quality Evaluation for White Spruce Plantations Using Discriminant Analysis
1985
Harding, R. B. | Grigal, D. F. | White, E. H.
Fifty-six study plots were established in fully-stocked white spruce plantations, 33 to 43 yr old, in northern Minnesota. The plots were separated into three growth response groups based on site index, basal area, and mean annual biomass increment of the spruce. Discriminant analysis was used on data from 50 of the plots to determine the site descriptors that best separated the plots into their respective growth groups. The discriminant functions, based on seven descriptors, correctly classified 76% of the plots. Plots in groups 1, 2, and 3, roughly equivalent to good, medium, and poor productivity, were correctly classified 69%, 80%, and 79%, respectively. When individual plots were sequentially deleted from computation of the functions (jacknife analysis), these values dropped to 56%, 75%, and 71%, with an overall value of 68%. Three of the remaining six independent test cases were correctly classified. Slope, soil phosphorus, and nutrient synecological coordinates were all major discriminators. These discriminators represent physiographic, soil, and vegetation properties, and demonstrate the importance of the total site approach when defining site quality for white spruce.
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