During the last decade there has been increased interest in mixed species silvicultural systems throughout boreal and sub-boreal Canada. These silvicultural systems often rely on crop trees grown under shaded conditions for extended periods of time. Consequently, there is a need for additional information regarding tree performance in full or partial shade. Six different regions throughout British Columbia, Alberta and Saskatchewan were sampled for this project. In the first part of this project, we developed regional equations predicting (1) radial increment of juvenile aspen as a function of growing season light availability, and (2) radial and height increment of juvenile spruce as a function of growing season light availability and initial tree size. For spruce, radial growth showed an approximately linear increase with light levels, while height growth increased more asymptotically. For aspen, radial growth was found to increase asymptotically with light levels. Initial tree size was found to have a large effect on both spruce radial and height increment. No effect of initial tree size on aspen radial growth was found. Some regional differences in growth patterns were observed. These differences can probably be attributed to differences in macroclimate between the sampled regions. In the second part of this project, we determined species-specific crown openness for mature aspen and spruce. Aspen was found to have a higher openness than spruce in all sampled regions. Significant regional intraspecific differences in openness were found. The observed differences are small, and consequently unlikely to have large effects on stand dynamics or understory tree performance. The highest openness was observed in the western sampling regions, while lower openness was observed in the eastern sampling regions. We did not find any significant relations between openness and macro climatic variables.
Bruce C Larson.
Larson, Bruce C.. 2004. Modeling growth of juvenile aspen and white spruce in western boreal Canada: FII forest research program 2003/04 annual progress report. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2004MR222