The relative importance of competition, microsite, and climate in controlling the stem taper and profile shape in jack pine

Abstract

The purpose of this study was to identify the relative importance that environmental factors have on the taper and profile shape of mature jack pine (Pinusbanksiana Lamb.) stems. A total of 60 dominant trees from six different stands (10 per stand) were felled and measured to determine stem size, taper, and profile shape. Total height, basal age, and diameters at three locations (breast height, 20% total height, and 70% total height) were collected. The last two diameters were then used to calculate stem taper and profile shape. Data on competition (4 variables) and microsite (10 variables) were collected. Climatic variables (6) were interpolated from nearby weather station data. From the regression results, several environmental factors from all three categories (competition, microsite, and climate) proved to be important in determining taper and shape. The most relevant measures from each category, respectively, were percent canopy opening (taper) or total basal area (shape), slope, and growing degree-days. When combined in a multiple linear regression, these environmental variables, along with stand age, explained 61.9% of the variation in stem taper and 38.6% in stem shape. Although these values represent a significant portion of the variation in stem profile characteristics, further exploration into additional factors (e.g., bending and stress caused by wind action, nutrition, genetics) affecting stem taper and shape is required.