Effect of diameter limits and stand structure on relative density indices: A case study

Abstract

An understory of shade-tolerant species often develops in stands in the Douglas-fir region of western Washington and Oregon and can have a disproportionate effect on relative density indices, such as Reineke stand density index and Curtis relative density. The effects of such understories and of other departures from the even-aged condition are illustrated with selected stand data. In general, the summation methods are less influenced by departures from the even-aged condition than are the conventional calculations based on quadratic mean diameter. Recommendations are made for consistent definition of the lower diameter limit of trees to be included in such computations.