A species- and site-specific stand density index based on growth and mortality

Abstract

A stand density index (SDI) was derived from three hypotheses, of which two concern mortality and growth up to the age at which there is an inflection point in growth, and the third relates mean tree volume and dbh (quadratic mean diameter at breast height) up to that age. The equations are [Formula: see text] or [Formula: see text], reference dbh = 25.4 cm or 10 inches. The parameters λ and β relate mean tree volume to dbh and stand volume to number of trees. Either equation provides a simple alternative to determining the self-thinning line and finding its slope, and also provides a direct comparison to the Reineke equation. Comparison of SDI values and exponents from the above equations to others’ results indicates the equations tend to produce smaller exponents, and larger SDI values, for dbh less than 25.4 cm. Values of [Formula: see text] varied with species and site quality, generally with smaller values than 1.605 for conifers, and larger values for angiosperms, when these were determined from yield tables, while values from experimental plots were always smaller than those from yield tables. Parameters must be estimated from data that are not significantly beyond the inflection age, and β and the ratio of growth to mortality parameters must be comparable.