Buffaloberry [Shepherdia canadensis (L.) Nutt.] fruit production in fire-successional bear feeding sites

Abstract

Buffaloberry [Shepherdia canadensis (L.) Nutt.] fruits are the usual late-summer food for bears (Ursus spp.) in the Front Ranges of Banff National Park, but little is known about the effect of fire or other factors on fruit production. I assessed the association between fruit production (fruits m-2 of buffaloberry shrub) and environmental factors at 76 plots in Banff National Park and found a negative association with forest canopy cover. Forest canopy cover accounted for 70% of the variation in fruit production. Fruit production also decreased from NNE- to SSW- facing slopes, but this effect was small compared to the decrease associated with increasing forest canopy cover. Forty plots were re-established at or near the original 76 sites the following year. A strong negative association between fruit production and forest canopy cover again occurred, but there was no significant association between fruit production and slope aspect. Fruit production began 5 years after fire in 2 recent burns. In sites burned 23 and 25 years ago, fruit production was comparable to the recorded in older-aged burns, and already was low at one site in the 25-year-old burn where regenerating lodgepole pine (Pinus contorta Dougl.) canopy cover measured 72%. Many sites in older burns, however, have remained forest-free due to xeric site conditions, chinook wind, avalanching, or other factors. These open sites were associated with abundant fruit. Managers must consider the prolonged effects of fire when assessing relation ships among fire, forest canopy cover, and buffaloberry fruit production.