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Interactions of predominant insects and diseases with climate change in Douglas-fir forests of Western Oregon and Washington, USA
Agne, M., Peter A Beedlow, D. Shaw, D. Woodruff, E Henry Lee, S. Cline, AND R. Comeleo. Interactions of predominant insects and diseases with climate change in Douglas-fir forests of Western Oregon and Washington, USA. Society of American Foresters national convention, Albuquerque, NM, November 15 - 19, 2017.
By the end of the 21st century, climate models predict hotter, drier summers and warmer, wetter winters in the Pacific Northwest (PNW), resulting in decreased snowpack, earlier snowmelt, and increased summer water balance deficit. These changes are already affecting sensitive forested ecosystems, raising concerns that forests are becoming increasingly susceptible to land management practices, tree pathogens, phytophagous insects, and fires. There is an increasing interest in understanding the interactions of these biotic and abiotic disturbance agents to allow for prediction of future climate-mediated changes in forest ecosystems. WED scientists have taken a system-specific approach to disturbance regime characterization for the Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) region of the coastal PNW which is an important region for timber production, carbon sequestration, and wildlife habitat. WED scientists have concluded that the impacts of biotic and abiotic disturbance agents are substantial in this region, but knowledge of the interactions among disturbance agents is generally lacking. Our work is important for identifying and filling in the gaps of knowledge in understanding the complex interactions of temperature, water, and biotic disturbance agents on conifer forests in the PNW under climate change scenarios. As temperature rises and soil moisture decreases, how climate change impacts will manifest in the PNW will depend on the changing role of these forest disturbance regimes. This contributes to ACE CIVA 2.4.
Forest disturbance regimes are beginning to show evidence of climate-mediated shifts associated with global climate change, and these patterns will likely continue due to continuing changes in environmental conditions. Tree growth is controlled by the physiological constraints of temperature and moisture availability, but forest management, insect pests, pathogens, fire, and drought are important disturbance factors in many forest ecosystems. Understanding physiological, stand-level, and landscape-scale effects of important disturbance agents, as well as their interactions, is critical to predicting future trends in response to climate change and effects on ecosystem services. However, disturbance regimes are specific to a given forest type and are not easily generalizable. Here, we discuss the disturbance regime of Douglas-fir (Pseudotsuga menziesii) forests of the Coastal Pacific Northwest of North America as a model system to illustrate the complex interactions of the major disturbance factors in a forested ecosystem. We then examine historical and projected trends in regional climate, which can generally be described as “hotter, drier summers” and “warmer, wetter winters,” and discuss implications of these climate trends on the disturbance regime. Finally, we highlight important knowledge gaps in the understanding of this disturbance regime.