Growth and Ecophysiological Responses of Fraser Fir (Abies Fraseri) Christmas Trees Along an Elevational Gradient

Fraser fir (Abies fraseri) Christmas tree production is a $100 million dollar/year industry in North Carolina, but the future of these trees may be threatened by predicted global climate change. To evaluate how this species will respond to climate drivers associated with warming, I studied growth and ecophysiology of Fraser fir Christmas trees along an elevational gradient from 664 to 1228 m. Bud-burst occurred 6 days sooner, new shoots ceased elongation 10 days sooner, and trunk growth ended 8 days later at low elevations than at high elevations, indicating a lengthening of the growing season. Capacity for photosynthesis under standard conditions did not decrease with elevation, but did as needles aged. Diurnal patterns of gas exchange under ambient conditions were measured 3 times during the 2014 growing season, which showed that photosynthesis tended to peak earlier in the morning at low elevations, and that daily carbon gain was lowest at low elevations, primarily due to high temperatures above 30 degrees C. As climate change progresses, higher cloud ceilings, increased evaporative demand, and higher temperatures will further reduce growth and ecophysiological functioning at low elevation Christmas tree farms, but middle and high elevation farms may benefit from a longer growing season.