Environmental Microbiology: Tannins & Microbial Decomposition of Leaves on the Forest Floor

Abstract

Tannins are plant chemicals that humans find useful in products as diverse as tea and leather. Why do plants produce these compounds? One possible answer is defense against pathogens and herbivores. In this series of laboratory exercises, student inquiry begins with a simple question: What happens to the multitude of leaves that drop each autumn? This inquiry brings students from the outdoors to the laboratory, where they observe differences in leaf decomposition rates and the natural abundance of bacteria and tannin concentrations in leaf tissues of red oak, white oak, and tulip poplar. In the process, students increase their understanding of plant chemistry, bacterial culture, graphing, and natural history, while experiencing the iterative nature of scientific inquiry.