Comparison of maximum size–density relationships based on alternate stand attributes for predicting tree numbers and stand growth

Quantification of site occupancy or stand density is essential for modeling forest stand mortality, growth and yield. A variety of measures of stand density have been proposed. Diverse tree and stand attributes have been employed, but direct comparisons of the effectiveness of various measures for estimating number of trees for fully stocked stands and for predicting growth for stands at different stages of development are not possible due to the varying forms of the measures.Maximum size–density relationships are a widely-used type of stand density measure. Reineke’s stand density index (SDI), which is based on number of stems per unit area and quadratic mean stem diameter, is the most commonly-applied stand density measure of this type. In the study reported here, stand density indices were developed by employing the structure of Reineke’s index but using the stand attributes of mean stem volume and mean stand height, as well as mean stem diameter. When estimating number of trees and periodic volume growth per unit area using data from sample plots in planted stands of loblolly pine, the SDI based on mean diameter performed best with mean stem volume being second best and mean stand height third.

► Comparisons are made of stand density indices based on diameter, height and volume.
► A common modeling framework is employed.
► Results show that diameter is best, volume second best and height third best.