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Patterns of Increasing Swiss Needle Cast Impacts on Growth of 20- and 40-year-old Douglas-fir from Tillamook
Lee, E., S. Cline, AND M. Bollman. Patterns of Increasing Swiss Needle Cast Impacts on Growth of 20- and 40-year-old Douglas-fir from Tillamook. Swiss Needle Cast Cooperative Annual Meeting, Corvallis, OR, November 07, 2017.
Douglas-fir (Pseudotsuga menziesii var. menziesii (Mirb.) Franco) is a dominant PNW tree species that is infected by the foliar fungus Phaecryptopus gaeumannii (Rhode) Petrak which causes Swiss needle cast (SNC) disease. Currently, SNC is causing an epidemic west of the Oregon Coast Range from Coos Bay to Astoria. The most severely infected Douglas-fir stands are located in Tillamook, Oregon where environmental conditions are highly favorable for fungal development. Increasing severity of SNC has reduced the growth of naturally regenerated Douglas-fir stands since ~1984 due to increasing winter temperatures associated with climate change. WED scientists reconstructed the history of SNC impacts on 20- and 40-year-old Douglas-fir trees growing on Stimson Lumber land in Tillamook. Our work is important for filling in the gaps of knowledge in understanding the complex interactions of temperature, water, and biotic disturbance agents on naturally-regenerated and introduced conifer stands in the PNW under climate change scenarios. Because the greatest warming due to climate change is predicted to occur in the winter and summer, SNC is expected to intensify in frequency and magnitude at higher elevations and/or higher latitudes along the coast and inland where current winter temperatures are a primary limiting factor to fungal growth. SNC in combination with climate stress are predicted to decrease forest health and condition. This Abstract contributes to CIVA-2.4.
Currently, Swiss Needle Cast (SNC) is causing an epidemic west of the Oregon Coast Range from Coos Bay to Astoria. The most severely infected Douglas-fir trees are located on BLM land and Stimson Lumber plantations in Tillamook where environmental conditions are highly favorable for fungal development. Increasing severity of SNC has reduced the growth of naturally regenerated and introduced Douglas-fir stands since ~1984. Annual radial stem growth of 20- and 40-year-old Douglas-fir trees on Stimson Lumber land in Tillamook displayed a marked decline in growth rates in the most recent decade. The increase in SNC severity is associated with increasing winter temperature which enhances the proliferation of pseudothecia and inoculum abundance.