Development of a management plan for coast live oak forests affected by sudden oak death in East Bay Regional Parks

Abstract

The East Bay Regional Park District maintains the largest urban park system in the United States, comprising over 45 000 ha, and more than 1900 km of trails, with extensive forests bordering residential areas. Sudden oak death (SOD), caused by the introduced oomycete Phytophthora ramorum, was first detected in a district park in 2001. Both increased fire risk and structural failure of large trees located near sites with heavy public usage are concerns for managers. Management requires reliable data about the location and severity of the disease. To produce disease incidence and risk maps, between 2008 and 2013 we placed 537 georeferenced 10-m radius fixed plots in oak-bay stands in five parks in the East Bay Hills in the San Francisco Bay Area. We recorded data for all woody vegetation and the disease status of coast live oaks. Between 6 and 17 percent of coast live oaks were symptomatic and 2 to 8 percent were dead with symptoms of SOD. Infection rates of 2.1 and 3 percent/year were estimated for Tilden Park and Huckleberry Preserve, respectively. Logistic regression analysis for Anthony Chabot Park identified two predictors of SOD incidence: topographic moisture indices and increasing coast live oak diameter at breast height (1.37 m; DBH). Model results for the other parks confirm that DBH is a significant predictor of SOD infection. Modeled results for the other four parks found consistently significant associations between symptomatic coast live oak and remote sensing derived tasseled cap greenness vegetation index values, and distance to stream channels.

Parent Publication

• Proceedings of the seventh California oak symposium: managing oak woodlands in a dynamic world

Citation

McPherson, Brice A.; O’Neill, Joshua; Biging, Gregory; Kelly, Maggi; Wood, David L. 2015. Development of a management plan for coast live oak forests affected by sudden oak death in East Bay Regional Parks. In: Standiford, Richard B.; Purcell, Kathryn L., tech. cords. Proceedings of the seventh California oak symposium: managing oak woodlands in a dynamic world. Gen. Tech. Rep. PSW-GTR-251. Berkeley, CA: U.S. Department of Agriculture, Forest Service, Pacific Southwest Research Station: 553-561.