Wednesday, November 15, 2006 - 9:30 AM

Bioenergetic Electron Flow Diagrams: A Powerful Tool for Teaching Biogeochemical Cycling in Soil and Beyond.

Nick Balster and Robin Harris. Dept. of Soil Science, Univ. of WI, 1525 Observatory Dr., Madison, WI 53706-1299

Understanding soil chemistry and its link to nutrient cycling rests upon a foundation in biogeochemistry where the interaction between the soil biology and chemical substrates are quantified. Moreover, this foundation requires knowledge and skill in basic thermodynamics, electron flow, and redox, subjects often difficult for university students to comprehend or to appreciate their relevance. Because these barriers persist, it is often difficult to teach such concepts, let alone solidify their use in lifelong learning beyond the classroom exam. We have developed a tool called Bioenergetic Electron Flow diagrams (BEF) that helps bridge this barrier such that students can easily predict and quantify (if needed) how the environment determines the organisms involved in the cycling of chemicals within soil and the potential of these selections to occur. The BEF diagrams are based on ranked electron transfer half reactions with pre-calculated standard and ambient electron transfer potentials. These diagrams can be used as a direct visualization of coupled electron donor and acceptor reactions for the identification of the relative energetics of the multitude of biological reactions in diverse soil systems. The educational advantage of this tool resides in the intuitive ease of its use in contrast to the classical non equilibrium biogeochemical approach that requires completely balanced reactions and labor-intensive quantitative derivations. Most important, this tool demystifies the geochemical litany of reactions that must be understood to make informed quantitative predictions of the cycling of soil chemicals and the organisms that mediate their movement and storage.