Risk Analysis and Guidelines for Harvest Activities in Wisconsin Oak Timberlands to Minimize Oak Wilt Threat

Oaks (Quercus spp.) are an important species group in the forests of Wisconsin. The State's timberland typed as oak-hickory forest was estimated at 2.9 million acres in 1996. Growing stock volume for red oak was estimated at 2.4 billion cubic feet, whereas select white oak volume was estimated to be 927 million cubic feet. Oak wilt, the oak disease of greatest concern in Wisconsin, is widespread in the lower two-thirds of the State. Harvest activities in oak stands may result in introduction of the disease agent, Ceratocystis fagacearum, into the stand or promote intensification of the disease within the stands or both. A risk-rating system based on scientific- and experience-based knowledge was used to develop a statewide system for oak wilt risk analysis. Guidelines for timber harvest activities in oak stands were then developed based on results of the risk analysis. The analysis and recommendations have been published (http://www.dnr.state.wi.us/forestry/fh/oakWilt/guidelines.asp) in three different formats. The formats include a pdf version of decision-trees with accompanying tables, a simple spreadsheet application allowing the user to obtain specific guidelines based on his/her response to five questions about the stand and timing under consideration, and an interactive online format derived from the spreadsheet version. The query page of the interactive formats is linked to a concealed table containing the risk analysis and recommendation matrix. The tool provides consistent, statewide guidelines for harvest activities that will, when applied, minimize spread and reduce the biological and economic impacts of oak wilt to Wisconsin’s oak timberlands. The rule-based, expert-driven system approach used to develop these guidelines could be used to assess risk and develop large-scale management guidelines for other established forest pathogens.