Post-fire conifer regrowth in upper subalpine Grouseberry (Vaccinium scoparium) habitat used by Grizzly Bear (Ursus arctos) in Banff National Park, Alberta

Abstract

Grouseberry (Vaccinium scoparium) communities in many open, upper subalpine sites within Banff National Park have abundant conifer seedlings, saplings, and small trees. Because fruit production typically decreases with increasing forest canopy cover, we predict that infilling by conifers will lead to reduced Grouseberry fruit availability for wildlife, including Grizzly Bear (Ursus arctos), a Threatened species in Alberta. We studied conifer recruitment in Grouseberry communities within recent (2001 prescribed fire) and old (1920 and 1889) burns in Banff National Park during 2008–2022. Most (55%) of the conifers in our plots were Engelmann Spruce (Picea engelmannii); an additional 34% were Subalpine Fir (Abies lasiocarpa), 11%, Lodgepole Pine (Pinus contorta), and <1%, Subalpine Larch (Larix lyallii). The density of small conifers (height >30 cm, diameter <10 cm) did not vary in communities that were 21, 102, and 133 years post-fire, but was lower in the 2001 burn 6–7 years post-fire. The mean density of small conifers in the 2001 prescribed burn increased from 15 ± 18 (SD) stems/100 m² in 2007–2008 (6–7 years post-fire) to 73 ± 67 stems/100 m² in 2022 (21 years post-fire). Conifer ingrowth has the potential to overgrow and shade Grouseberry habitat, with declining fruit production a predicted consequence. However, in Banff National Park, where lightning-caused fires are rare, managers have the option of applying prescribed fire to create openings in the upper subalpine forest and thus enhance fruit production in Grouseberry and other fruiting shrubs important to wildlife.