Contrasting effects from snow cover manipulation on two dwarf shrubs along an altitudinal gradient – an investigation on the phenology and performance of Vaccinium myrtillus and Vaccinium vitis-idaea

Abstract

Vaccinium myrtillus and Vaccinium vitis-idaea are key species in boreal ecosystems due to their abundance in biomass, flowering and berry production, yet we know little about how they are affected by ongoing climate change. Current knowledge suggests that snow cover extent and properties have and will change considerably with climate change. The principal objectives of this study were to investigate the effects from spring snow cover manipulation on phenology and performance of the early-flowering Vaccinium myrtillus and the later-flowering Vaccinium vitis-idaea along a climate gradient. In order to investigate this, the snow cover was manipulated at three altitudes containing the study species at ca 150, 500 and 900m asl in Sogn, Western Norway in order to advance and delay snow melt timing. Snow was manipulated through shovelling, then followed observation of the phenophases, counting of flowers and berries as well as measurements of growth over the growth season of 2018. Altitude was the main factor explaining phenophases for both species. Still, varied effects on phenology was found in V. myrtillus along the gradient. Phenology in this species was positively affected by snow melt delay at low altitudes, but not at higher altitudes. Combined effects between elevation and snow cover manipulation were not found in reproduction and growth, but snow melt advance negatively affected reproduction. Vaccinium vitis-idaea proved resilient to the snow cover manipulation, with only minor delay in flower formation. The findings in this study suggests that the early-flowering V. myrtillus will be negatively affected by reduced snow cover at low altitudes in Western Norway, while Vaccinium vitis-idaea is likely to withstand future changes at all altitudes. Responses because of experimentally induced snow change were different between species and along the altitudinal gradient for V. myrtillus. With this, the understanding of dwarf shrubs has increased ever so slightly.