Two stem analysis data sets were used in this evaluation (Map1). The first data set was from Canadian Forest Products and was obtained for trembling aspen and white spruce in the lower foothills natural subregion. The second stem analysis data set came from Alberta Pacific Forest Industries and sample trees for white spruce and trembling aspen came from the central mixedwood natural subregion. Trees were randomly selected for sampling representing different canopy positions (dominant, co-dominant, intermediate and suppressed). The sample tree was sectioned at regular intervals along the stem. Tree sections or tree cookies were cut from the top end of each tree section. The length of each tree section or bolt was recorded. Several tree level measurements were also taken in the sampling including breast height age, stumpage, total tree height diameter at breast height, species and canopy position. The sample discs were taken back to the lab and were sanded to ensure that the section ages were accurate. The dependent variable in this study was the growth increment tree height ratio while the independent variables were tree age, tree height, section increment and species.
Sample Size for white spruce and trembling aspen in the central mixedwoods and lower foothills natural subregions in Alberta (Figure 1 and 2)
Calculations for tree increment tree height ratios.
Once the sample discs were collected for each tree they were aged and diameters were measured, both outside and inside bark (Figure 3). The data was entered into a table format for each tree in the sample. Each individual tree section was entered into the data set as a separate record along with the cumulative height. Each sample tree is represented as a series of separate tree lengths in the table. All of the sections add up to the total tree height. The same calculations were completed for all white spruce and trembling aspen sample trees. Graphs were then completed showing growth increment tree height ratios for tree age and tree height by species in each natural subregion. Trembling aspen was compared to white spruce in this research study. A comparison was made between species and within white spruce for the lower foothills based on canopy position. This was not done for white spruce in the central mixedwood natural subregion as canopy position was not measured in the sample data