JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. This content downloaded from 202.28.191.34 on Sun, Abstract. The weight loss and changes in the concentrations of major classes of macromolecules were assessed in white oak (Quercus alba) and pignut hickory (Carya glabra) during processing in a third order hardwater stream in southwestern Michigan.Oak was processed more slowly than hickory. An initial rapid weight loss in hickory was followed by a linear rate of loss, while oak lost weight at a linear rate over the entire processing period.Losses of soluble reducing sugars and polyphenols were rapid, occurring mainly during the initial 2-wk exposure to the stream. Hemicellulose and cellulose losses were similar in both species and nearly paralleled weight loss. An absolute increase in the lignin fraction was observed in both species during the first 6-12 wk of processing. We consider this to be due to an increase of complexed N containing compounds in the lignin fraction. Lipid loss was intermediate between soluble sugars and polyphenols and the structural components. Of the constituents analyzed, only the concentration of Kjeldahl nitrogen and lipid was significantly higher in hickory than in oak leaves during the entire processing period.