Interactions of predominant insects and diseases with climate change in Douglas-fir forests of western Oregon and Washington, U.S.A.
Citation:
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, U.S.A. FOREST ECOLOGY AND MANAGEMENT. Elsevier Science Ltd, New York, NY, 409:317-332, (2018).
Impact/Purpose:
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. Forest disturbance regimes are beginning to show evidence of climate-mediated shifts associated with climate change, raising concerns that forested ecosystems are becoming increasingly susceptible to forest management, tree pathogens, phytophagous insects, and fires. Understanding the physiological effects of climate and the important disturbance agents on forested watersheds and ecosystem services is critical to predicting future trends in response to climate change. EPA scientists in collaboration with the U.S. Forest Service reviewed the disturbance regime of Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) forests of the Coastal Pacific Northwest (CPNW) of North America as a model system to illustrate the complex interactions of biotic and abiotic factors in a forested ecosystem. The historical disturbance regime in CPNW Douglas-fir forests consists of long-term fire return intervals interacting with biotic and abiotic factors that then interact with forest management. A key finding is the climate-disturbance interactions vary across the region depending on topographic and edaphic conditions, consequently, generalizations beyond the region are limited. While the impacts of individual disturbance agents on Douglas-fir forests are relatively well-understood, knowledge of the interactions among disturbance agents is generally lacking. The impacts of biotic and abiotic disturbance agents on this forest type are substantial and it is important to include these disturbance effects, in addition to constraints of temperature and moisture, in models of forested ecosystems to understand how forests may change in the future. Our work is important for filling in the gaps of knowledge in understanding the complex interactions of temperature, water, and biotic disturbance agents on conifer forests in the CPNW under climate change scenarios. This article contributes to ACE CIVA 2.4.
Description:
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 largely 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 the 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 and forest ecosystems. Finally, we highlight important knowledge gaps in the understanding of this disturbance regime in Pacific Northwest coastal forests.
