Climate effects on red alder growth in the Pacific Northwest of North America

Abstract

We investigated the effects of climate on the growth of red alder across a broad latitudinal gradient and over a wide range of growing conditions in the Pacific Northwest of North America (PNW). Data for this study came from a study established in 1988 that includes 31 research installations located between the Pacific Coast and the Cascade Mountains in Oregon, Washington, and British Columbia. The growth-climate model developed includes: summer heat moisture index (SHM), mean warmest month temperature (MWMT), spring precipitation (PPTsp), and initial height; and captures 78% of the variation in red alder volume increment. Based on this model, estimates of potential future growth were generated for three climate scenarios (i.e., cccma_cgcm3_A2-run4 ‘warm and wet’ of the Canadian Centre for Climate Modeling and Analysis; and ukmo_hadcm3_B1-run1 ‘cool and moist’ and ukmo_HadGEM1_A1B-run1 ‘hot and dry’ of the Hadley Centre for Climate Prediction and Research). These projections indicate a potential increase in volume increment of up-to 12% by the 2080s. Range-wide maps were generated for the volume increment potential (VIP) for the reference normal period 1961–1990, for the ‘warm and wet’ climate scenario, and the 2050s time period, suggesting that climate change may cause a substantial shift in the range and productivity of red alder in the PNW. In addition, maps of the predicted VIP of red alder for the Campbell River District in BC were generated and indicate an overall increase in projected growth of red alder. This study provides evidence that climate change will likely lead to expansion of the range and potential increases in growth for red alder in conjunction with assisted migration of provenance in the PNW. While these results indicate potential increased opportunities for extension of the range of red alder and opportunities for its management, care must be taken to avoid planting alder on sites with high risk of damaging agents such as cold outflow winds, frost, or drought.