Effectiveness of basal area for estimating canopy cover of ponderosa pine

Basal area is commonly used as a measure of canopy cover when describing overstory-understory relationships in forest ecosystems. We evaluated basal area and a number of other biotic and abiotic variables from 61 stands along the Rocky Mountain Front Range to establish whether this procedure has scientific merit and ascertain whether other models might provide a more precise estimator. Only basal area was correlated to overstory canopy and that relationship broke down above a canopy cover of 60%. Quadratic and piecewise linear models both provided an adequate fit of data over all stands sampled, however, the latter was regarded as better because (1) it reflected the straight-line relationship found below 60% canopy cover and (2) it objectively estimated the change-over point from a positively correlated model to one of no correlation. Basal area explained about 83% of the variation in canopy cover in both models. (C) 1997 Elsevier Science B.V.