Evaluating the Effectiveness of Restoration Treatments to Enhance Oregon White Oak Systems within the Klickitat River Watershed

Oregon white oak (Quercus garryanna) and associated plant communities provide key habitat to a number of plant and animal species, including Washington state listed threatened populations of Western grey squirrel. Over the past 150 years, human actions such as logging, fire suppression and grazing have altered stand structure and species composition of oak systems, reducing the extent and quality of historic Oregon white oak habitat. Oregon white oak and associated habitats are common in Klickitat County, which has one of the largest remaining acreages of Oregon white oak systems in the state of Washington. While most oak systems in the Pacific Northwest are found on private lands, Klickitat County contains a significant percentage of oak resources under public ownership, which provides unparalleled opportunities for landscape level management of oak systems. One management strategy public agencies and private landowners have been using to restore oak woodlands and savannas is oak release, in which conifers are removed or doghair oak stands are thinned to enhance stand conditions, improve wildlife features, and reduce the risk of habitat destroying fire. I examined the response of Oregon white oak trees thirteen years post-treatment, evaluating oak growth, seedling and cut stump responses, fuel load accumulation and changes in snag abundance, and compared these findings to untreated areas. Oak diameter, height and live-crown ratio were not significantly influenced by treatment; however, released stands displayed greater increases in tree diameters than were observed in control groups. Seedling and sapling recruitment of released stands were both significantly different from control stands. Logistic regression showed that percent canopy cover was a significant factor in determining the probability of oak stump sprout. Fuel treatments during release successfully reduced the amount of surface fuels across the study site, however overall fuel height increased between the study years. Lastly, snag abundance declined between the study years. I recommended management strategies for future implementation and protocol modifications for subsequent monitoring to help evaluate long-term release impacts