Evaluating the Ecological Integrity of Structural Stand Density Management Models Developed for Boreal Conifers

Density management decision-support systems (e.g., modular-based structural stand density management models (SSDMMs)), which are built upon the modeling platform used to develop stand density management diagrams, incorporate a number of functional relationships derived from forest production theory and quantitative ecology. Empirically, however, the ecological integrity of these systems has not been verified and hence the degree of their compliance with expected ecological axioms is unknown. Consequently, the objective of this study was to evaluate the ecological integrity of six SSDMMs developed for black spruce (Picea mariana) and jack pine (Pinus banksiana) stand-types (natural-origin and planted upland black spruce and jack pine stands, upland natural-origin black spruce and jack pine mixtures, and natural-origin lowland black spruce stands). The assessment included the determination of the biological reasonableness of model predictions by determining the degree of consistency between predicted developmental patterns and those expected from known ecological axioms derived from even-aged stand dynamics theoretical constructs, employing Bakuzis graphical matrices. Although the results indicated the SSDMMs performed well, a notable departure from expectation was a possible systematic site quality effect on the asymptotic yield-density relationships. Combining these results with confirmatory evidence derived from the literature suggest that the site-invariant self-thinning axiom may be untenable for certain stand-types.