Estimating site index from tree species composition in mixed stands of upland eastern hardwoods: Should shrubs be included?This article is part of a larger document. View the larger document here.
Site index is the most widely used method for site quality assessment in hardwood forests of the eastern United States. Its application in most oak (Quercus sp. L.) dominated stands is often problematic, however, because available sample trees usually do not meet important underlying assumptions of the method. A prototype method for predicting site index from tree species composition has shown promising results in the southern Appalachian Mountains. The objective of this study was to determine if upland oak site index was associated with two common understory shrubs: mountain laurel (Kalmia latifolia (L) and spice bush (Lindera benzoin (L) Blume). Regression analysis indicated that including these shrubs in the model increased r2 from 0.63 to 0.67. Predicted upland oak site index decreased by 5.4 ft if mountain laurel was present on a sample plot and increased by 7.4 ft if spice bush was present. Results from this exploratory study conducted in a small watershed should be validated elsewhere, but the findings do suggest that estimates of upland oak site index using the species composition method can be improved by observing the presence of mountain laurel and spice bush.