Abstract

Topic: Moose and forestry

Shrubs, moose, and forest overstory: understanding the effects of stand characteristics on essential forage from ericaceous shrubs.

Laura Juvany¹, Annika Felton², Per-Ola Hedwall², Adam Felton², Karin Öhman³, Märtha Wallgren⁴, Anders Jarnemo⁵, Christer Kalén⁶

Department of Wildlife, Fish and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden
Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, Alnarp, Sweden
Department of Forest Resource Management, Swedish University of Agricultural Sciences, Umeå, Sweden
Department of Wildlife, Fish, and Environmental Studies, Swedish University of Agricultural Sciences, Umeå, Sweden, Forestry Research Institute of Sweden, Uppsala, Sweden.
School of Business, Innovation and Sustainability, Halmstad University, Halmstad, Sweden
Swedish Forest Agency, Borås, Sweden.

Shrubs of the family Ericaceae are crucial in the diets of moose (Alces alces) and other cervids (family Cervidae) in Sweden. Bilberry (Vaccinium myrtillus), cowberry (V. vitis-idaea) and heather (Calluna vulgaris) often dominate the understory of boreal and temperate forests. These foundation species provide many essential ecosystem services, influencing carbon and nutrient cycles, serving as an important food resource for many species, and offering economic and cultural benefits as non-timber forest products. However, forestry-induced changes to the tree layer are thought to have reduced habitat suitability and abundance of these shrubs in Sweden. In the project ERICA, we examined how forest overstory influences these ericaceous shrubs by quantifying how stand characteristics from the most abundant forest types in Sweden, Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) dominated forests, shaped the above-ground biomass, growth, morphology and macro-nutritional composition of the shrubs. We determined that spruce dominated stands had comparatively less above-ground biomass of the three focal species than pine dominated stands; their plants were also of shorter stature, and a larger proportion of their biomass provided suitable forage for cervids. These shorter shrubs also provided a larger proportion of new shoot biomass and had a different macronutrient composition compared to shrubs growing in more open stands. The macronutrient composition of bilberry and cowberry shrubs growing in denser and more spruce dominated forests, aligned more closely with the nutritional target of moose, containing less non-structural carbohydrates, but more protein, compared to shrubs growing in more open and pine dominated forests. These findings indicate that forest owners’ decisions regarding tree species composition and forest stand density shape the shrubs’ characteristics, influencing their abundance and eventually, having an impact on the nutritional landscape for moose and other herbivores.