Evaluating the construction and effectiveness of slash walls at the perimeter of regeneration harvests to exclude deer

Abstract

Deer impacts on forest vegetation have complicated attempts at forest regeneration in many parts of the Northeast, Mid-Atlantic States, and other regions. Deer overabundance limits the success of forest regeneration. One strategy is to reduce deer browsing by temporarily excluding them from regeneration harvests. Because of the costs of fence installation, maintenance, and removal, we developed and tested the feasibility and effectiveness of slash walls. In 2017, 4 regeneration harvests ranging from 4.5 to 30 ha were cut. Slash and trees of marginal value proximate to the perimeter were piled into a slash wall that averaged 3.7 m to the tallest branch and 7.2 m wide. Slash walls occupied from 0.5 to 1.5 ha of the harvest area and used approximately 28,000 kg of slash and low-grade logs per 30 m section. The rate of construction depended on topography along with access to slash and low-grade trees. Construction rates for slash walls varied from 32 m/hr to 77 m/hr. The average cost of construction was $4.82/m ($1.47/ft) based on machine and operator costs of $200 (US)/hr for a weighted average cost of $541/ha ($219/ac). Fence installation can cost 3–4 times as much as slash wall construction, plus additional costs for maintenance and removal. The cost to monitor and maintain slash walls was negligible. Slash wall heights slumped approximately 8–14% per year, which reduced slash wall height by 37 cm per year. Four years after creating the slash walls, the heights of tagged seedlings of palatable species remained significantly greater inside the slash wall where deer were excluded than in adjacent control areas that were accessible to deer. We recommend slash walls minimally be constructed 3.1 m tall to the highest 5-cm-diameter branch, 7 m wide at the base, and sufficiently dense to prevent deer from being able to crawl through. This study is the first documentation of slash walls as a feasible and effective technique during regeneration harvesting to exclude deer from impacting forest vegetation. Subsequent to this study, multiple logging crews have created additional slash walls in CT, MA, NH, NY, and RI as part of commercial harvests.