Effectiveness of Bare-root and Gravel-culture Shrubs Used in Wildlife Habitat Restoration on Lakeshores in Northern Wisconsin

Abstract

Human development on lakeshore habitats has greatly reduced shrub layer coverage along many North American lakes, negatively impacting associated floral and faunal communities. In northern Wisconsin, several restoration projects have been implemented in recent decades to reverse the impacts of development on lakeshore natural communities. However, restoration practitioners are frequently limited to using containerized plant stock purchased at local nurseries, which can be cost-prohibitive. As an alternative, we tested the effectiveness of using dormant bare-root shrubs in restoration projects along five lakeshores in northern Wisconsin. Because bare-root plant stock can only be planted during narrow windows during the late fall and early spring, we examined the efficacy of using bare-root stock that was grown in a gravel medium (“gravel-culture”) and then planted later during the growing season. We monitored individuals from five species of native shrubs in each of three planting treatments over a three-year period and used a repeated measures, mixed-model approach to compare plant growth of both bare-root and gravel culture stock to growth of containerized stock. Logistic regression models were used to compare the survival of shrubs and treatments. Containerized stock exhibited the greatest growth and survival of the stock types examined. The utility of bare-root and gravel-culture stock varied among species, but for most species our results suggest that gravel-culture may be successfully used to extend the planting window.