Abstract
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.
Highlights
The complexity of density management decision-making for traditional volumetric-based objectives has been greatly reduced with the introduction of stand density management diagrams (SDMDs; e.g., [1–3])
Determining the degree of consistency between predicted developmental patterns and those expected from known ecological axioms derived from even-aged stand dynamics, represents an important step in this process
For reference purposes, the principal concept or relationship being evaluated is denoted in individual subgraphs using the following abbreviated subtitles (n., matrix position denoted in parentheses): Site Curves (1:1), Site Form (1:2), Sukatschew Effect
Summary
The complexity of density management decision-making for traditional volumetric-based objectives has been greatly reduced with the introduction of stand density management diagrams (SDMDs; e.g., [1–3]). Classified as stand-level distance-independent average tree models within the context of the forest modeling nomenclature [4], SDMDs can be subdivided into either static or dynamic types depending on their ability to describe density change dynamics throughout the rotation [5]. The latter type explicitly accounts for density-dependent mortality throughout all stages of stand development via the inclusion of a mortality submodel whereas the former type does not. The modular-based structural stand density management model (SSDMM) was developed.
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