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Journal of Undergraduate Research

Keywords

chemical defense, quaking aspen, resource conservation, Populus Tremuloides

College

Life Sciences

Department

Plant and Wildlife Sciences

Abstract

Browse damage to the quaking aspen (Populus Tremuloides) has dramatically increased in recent years due to proliferate wildlife densities, especially elk, in the central Rocky Mountains (Kaye et al. 2005). To protect itself from this, the quaking aspen produces chemical compounds called phenolic glycosides which deter wildlife from browsing the leaves. While the quaking aspen is known to increase the levels of these compounds in response to herbivory (Young et al. 2010), it is unknown whether these increases effect the entire canopy or only locations that are vulnerable to browsing. The purpose of this project was to test whether highly browsed areas of the aspen canopy are more strongly defended than other, more out-of-reach locations. By varying defense compound concentrations throughout the canopy, the quaking aspen can theoretically conserve resources that would otherwise be used for full canopy defense. The hypothesis states that mature and juvenile aspen trees will show higher concentrations of defense chemistry in the lower versus the upper canopy as this area is more easily browsed by local wildlife. Aspen suckers were hypothesized to have increased phenolic glycoside concentrations in the upper canopy where they are more heavily browsed.

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