Variable-quality form in mature jack pine stands: quantification and relationship with environmental factors
1992
Morris, D.M. | Parker, W.H.
The purpose of this study was to determine quantitatively to what extent various stem, crown, and branching attributes conformed to subjective evaluations of form for jack pine (Pinus banksiana Lamb.) in northwestern Ontario and which environmental variables were associated with the form-related variation. Six fire-origin stands established on deep soils were selected on the basis of their form and subjectively evaluated as good (2), medium (2), or poor quality (2). Ten dominant trees were randomly chosen from each stand, and 26 attributes were determined for each sampled tree. These attributes were categorized as growth (2), stem form (6), crown form (6), or branch characters (12). Data on surrounding stand conditions and microsite were also collected. Climatic factors for each stand were interpolated from nearby weather station data. These data were analyzed by canonical discriminant analysis. The first function separated the poor-quality stands from the other two classes, while the second function separated the average- from the good-quality stands. Important variables in the first canonical function were related to stem and crown characters, whereas branch characters were also important in the second canonical function. First and second canonical discriminant axis scores were used as two new summary variables representing quantified estimates of jack pine form and were regressed against environmental data. While competition and spacing variables explained much of the observed variation, climatic and soil moisture variables were also important. From the present results it is unclear whether these variables affect form directly or indirectly by modifying competition and spacing variables over the course of stand development.
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