A Study Of Autumn Olive (Elaeagnus Umbellata) Phenology And Associated Physiological Traits That May Facilitate Its Invasion Of The Understory Of A Southern Appalachian Forest

Elaeagnus umbellata, better known as Autumn Olive (AO), is an exotic tree species that has invaded much of the United States. It grows in a variety of habitats, but little is known about its ability to invade and persist in forest understories, especially at high elevations. AO may take advantage of high light conditions before canopy leaf out and after canopy leaf fall by leafing out early and maintaining leaves late into the fall. The use of an extended leaf phenology allows autumn olive to gain most of its carbon during these high light times. To address this hypothesis, I made phenological and gas exchange measurements throughout 2017. AO began leafing out in mid-February whereas native understory species didn’t leaf out until early April, and canopy trees until mid-April. The monthly diurnal measurements found that rates of carbon dioxide uptake by AO were higher in spring and fall when light levels were higher versus in summer when they were lower, suggesting that most of its annual carbon is gained during those periods when the overstory is leafless. The nearly two months of extended phenology gives AO a physiological advantage over native species, thereby contributing to its invasiveness.