Sperling, A.J., B. D. Pinno and R.E. Froese . 2025.
Abstract
Pre-commercial thinning has potential to mitigate the effect of drought stress on growth but likely
removes protection from environmental temperature extremes. Processes driving growth after
density management are poorly understood but important when applying thinning to stands that
will grow under future warmer and drier conditions. Consequently, we evaluated microclimate and
resource availability in operational scale pre-commercial thinning trials (treated and control) of
young (19-year-old) boreal trembling aspen/white spruce mixedwoods in northern Alberta,
Canada. Thinned stands in this study experienced more temperature extremes, both <0°C and
>30°C, than unthinned stands as well as the same quantity of extreme low soil moisture values.
However, lower tree density in thinned stands provided more available heat and higher average
soil moisture, especially during dry periods in the year. Soil nutrient supply rates were not
different between treatments, nor was soil moisture during wet periods, nor was soil temperature
in the early and late parts of the growing season. Regeneration of broadleaf trees species in
thinned stands was substantial. Overall, pre-commercial thinning caused both positive and
negative changes to the tree-growing environment.
Key Words
Silviculture; pre-commercial thinning; density management; microclimate; trembling aspen; white spruce; climate change
