Bird Community Changes One Year Post-Wildfire in Mesic Temperate Rainforests: A Case Study in the H.J. Andrews Experimental Forest, Oregon, USA

In the Cascade region of the Pacific Northwest, the productive, mesic, Douglas-fir dominated temperate rainforest is experiencing an increase in wildfire frequency. As an area with a history of mixed severity fire regimes, there is a need to better understand the immediate, and often long-lasting, ecological impacts of these altered fire regimes on ecological functions. My study uses pre- and post-fire bird population data, fire severity, and remotely sensed pre-fire forest structure data in a long term ecological research site to assess the impacts of a wildfire one year post event using birds as bioindicators. Using non-metric multidimensional scaling as the ordination method, bird community patterns were visualized as shifting towards warmer microclimate, and towards a more complex forest, which affected an increase in community variation post-wildfire. Using general linear mixed models, Relativized differenced Normalized Burn Ratio (RdNBR) was found to be the most significant predictor of bird community turnover which was displayed through temporal beta diversity. The interactions with RdNBR and plantations show that at low RdNBR values, plantations tend to have higher temporal beta diversity turnover than old-growth plots. This pattern reverses at higher RdNBR values, where turnover in old-growth plots trends upwards while that in plantations trends downwards. Overall, my findings highlight the need to protect structural diversity in forests, aiming to have mixed severity wildfires that promote a complex avian community - something that will be increasingly important as wildfire regimes shift with climate change. By linking burn severity, forest structure, and bird community responses, my study provides a foundation for understanding how complex ecosystems reorganize after disturbance and adapt to a changing climate.