Time Series Analysis of Disturbance Impacts on the Pacific Northwest Regional Carbon Balance
Large tracts of forestland in the Northwestern U.S. are subject to recurrent clear-cut harvest, thinning, variable intensity fire, and insect outbreaks − with significant impacts on local and regional carbon balance. These forests also offer the opportunity for mitigation of climate change by acting as carbon sinks through positive net ecosystem production (NEP, the balance of net primary production and heterotrophic respiration) on undisturbed stands. The proposed research will examine decadal trends in climate, NEP, and NECB (net ecosystem carbon exchange = NEP – fire emissions – logging removals) in the Pacific Northwest region using a combination of time series Landsat data and ecosystem carbon cycle modeling. Our study area (WA, OR, ID, western MT) will extend across a broad climatic gradient from cool, mesic coastal forests used primarily for wood production, to drier forests on the east side of the Cascade Mountains, and into the Northern Rocky Mountains with its more continental climate regime and higher incidence of fire and insect outbreaks. Our study period, 1985-2012 includes a wide range of interannual climate variability, notably 2002 when the Biscuit Fire burned over 200,000 ha in Southwestern Oregon, and 2010, a strong La Nina year with virtually no wild fires in the region. Our results will inform deliberations about how best to manage regional forests in the face of climate warming.