The snow in the willows: assessing the use of shrub-willows for living snow fences in Minnesota, USA

Abstract

Blowing and drifting snow adversely affect winter driving conditions and road infrastructure in Minnesota, often requiring removal methods costly to the state and environment. Living snow fences (LSFs)—rows of trees, shrubs, or grasses installed on fields upwind of roadways—are economically viable solutions for controlling drifting snow in agricultural areas and can provide a range of environmental benefits, such as carbon sequestration and wildlife habitat. Despite incentives and financial assistance by state and federal agencies, farmer adoption of LSFs is low, in part due to concerns about removing cropland from production. Shrub-willows (Salix spp.) have been proposed as a LSF species to meet landowner needs, given their potential to reach effective snow fence heights and densities soon after planting and provide a marketable biomass product. As part of evaluating the use of willow LSFs for multiple benefits in Minnesota, this thesis sought to 1) assess the establishment and snow trapping ability of three willow varieties in two- and four-row planting arrangements in a LSF in south-central Minnesota, and 2) compare the establishment and growth of both native and hybrid shrub-willow varieties and species to species traditionally used in Minnesota LSFs (i.e., Gray dogwood and American cranberrybush). In the first study, willows had an average survival rate of 89% and average growth of 1 meter after two growing seasons. Over the 2014-15 winter, no differences were found among willow varieties in their ability to trap snow; however, four-row arrangements caught more snow than two-row arrangements. Blowing snow models indicated that two- and four-row arrangements should be able to trap all of the mean annual snow transport for the study region after three and four growing seasons, respectively. In the second study, all species showed good establishment, and all willows exceeded the growth of traditional LSF species after the second growing season. Additionally, a native willow (S. petiolaris) had similar growth to the top-growing hybrid willow varieties, suggesting it may provide a suitable local source for future LSFs. Overall, these results suggest that willows may provide effective LSFs earlier than traditional LSF species and add to the LSF design practices for transportation agencies, natural resource managers, and landowners.