A comparison of phenolic levels in Populus tremuloides across four ecosystems.

Abstract

The coevolution between plants and herbivores has produced a wide range of secondary metabolite defense adaptations in plants, one of the largest groups being phenolics. The carbon-nutrient balance hypothesis states that when the C:N ratio is high within a plant, more carbon-based secondary metabolites are created. Also, if C:N is low more primary metabolites are synthesized. We speculated that soil moisture would have an affect on C:N and thus secondary metabolite levels. We studied the differences in phenolic levels of the Populus tremuloides in four distinct ecosystems: swamp, moraine, high outwash plain, and low outwash plain. We found a significant difference between the constitutive phenolic levels of the samples from the four ecosystems (Kruskal-Wallis Statistic = 9.179, p = .027). Specifically, the high and low outwash and the moraine and low outwash were significantly different (p = .028 and p = .007 respectively) with the low outwash have the lowest amount of phenolics. We speculate this is due to lower soil moisture content in the low outwash plain, but other factos may also have had an effect. If soil moisture does have an affect on C:N and phenolic levels there are obvious consequences due to climate change from global warming.