Effect of Climate Change on Tannin Levels in Aspen and Birch

1. Effect of Climate Change on Tannin Levels in Aspen and Birch Yamini Karandikar, Ezra Schwartzberg (mentor), LindrothLab, Department of Entomology Aspen Birch ABSTRACT Tannins are used as a defense mechanism by plants to protect from herbivory. The Growth Differentiation Balance Hypothesis states that as plants gain the ability to grow faster, less energy is allocated towards defense. Under warmer growing conditions, such as those experienced under predicted future temperatures, we expect plants to grow faster and produce less condensed tannins. To test this, leaf samples from aspen and birch trees grown under control, +1.8, and +3.6 C temperature-controlled forest plots were analyzed for tannin content. We found that birch and aspen grown under higher temperatures have lower levels of condensed tannin. Big Picture How does this affect the boreal forest ecosystem? Although predators, herbivores, and plants initially experience a higher rate of growth with increasing temperatures, plant growth will level off and decline with further temperature increase. The boreal forest will be negatively impacted as a result of increased temperatures. Since aspen and birch produce less defensive chemicals at higher temperatures, the boreal forest will also be negatively impacted by increased herbivory. • BACKGROUND • Study on the effects of boreal forest warming • This map shows the worldwide distribution of boreal forests. • This study investigates the effects of warming on tannin levels in plant leaves. • Tannins characterized by an astringent taste • Found in all plant parts: flower, seeds, bark, wood, and protects plant from predation1 • Environmental factors and resource availability impacts tannin levels2 • Better growing conditions plants produce less tannin 2 • do not need as much protection • compensate for losses with more growth Results The plus 3.6 C0 treatment was found to be significantly different than the control and plus 1.8 treatments. D.F: 2, 34, F=2.76, p=.079<.100 The control treatment was found to be significantly different than the plus 1.8 and 3.6 C0 treatments. D.F: 2, 35, F=2.92, p=.069<.100 HYPOTHESIS Birch and aspen will have lower amounts of condensed tannin when grown under higher temperatures. Increase in temperature by 3.6 C0 causes a decrease in average % condensed tannin levels. Increase in temperature by 1.8 and 3.6 C0 causes a decrease in average % condensed tannin levels. METHODS Research site: leaf samples from Minnesota where the trees are all grown under the same condition except for temperature. • Treatment: • Aspen and Birch plants are grown under three different temperatures: control (normal temperature), +1.8 C, and +3.6 C. • Chemical analysis: • 25 mg of each leaf sample used for tannin extraction • extracted in a solution of acetone, water, and ascorbic acid with a centrifuge • Extracted tannin solution is diluted, acid butanol and an iron reagent is added. • Causes color change which is analyzed by a photo spectrometer Statistical Analysis: Used one-way ANOVA analysis of variance to determine if data was significantly different. References: 1Hollinger, J. "BornNaturalist:Anthocyanins." BornNaturalist: Home. Creative Commons, 26 June 2007. Web. 22 Nov. 2011. 2Reed, Jennifer, and Brian McCarthy. "Patterns of Leaf Tannin Variation in Chestnut Oak (QuercusPrinus) and Black Oak (QuercusVelutina) with Respect to Topography in a Southeastern Ohio Oak-Hickory Forest." Bulletin of the Torrey Botanical Club (1996). Print.