Links Between Litter Microbial Activity and the Resultant Biopolymer Chemistry of Decayed Litter Among Forest Floors of Different Age.
Timothy Filley1, Melissa McCormick2, D. Lee Taylor3, and Dennis Whigham2. (1) Purdue University, EAS Dept., 550 Stadium Mall Dr., West Lafayette, IN 47907, United States of America, (2) Smithsonian Environmental Research Center, 647 Contees Wharf Rd., Edgewater, MD 21037, (3) University of Alaska - Fairbanks; Institute of Arctic Biology, 311 Irving I Building, 902 N. Koyukuk Drive, Fairbanks, AK 99775-7000
The link between changes in litter quantity and the response of soil organic matter (SOM) pools is a research area of intensive study given the dramatic changes in land use and the proposed impacts that rising CO2 and surface temperatures may have on forest productivity. In a mixed deciduous forest at the Smithsonian EnvironmentalResearchCenter litter amendment plots were established in old (120-150 y) and young (50-70 y) forests. In May 2004, six plots were amended with locally collected Lirodendron tulipifera wood and leaves. Transformations to litter biopolymers, e.g. lignin and cutin/suberin, after one year of decay were tracked by alkaline CuO extraction. Cutin and suberin were assessed by analysis of extracted hydroxyl and alkoxy-substituted fatty acids (SFA). Resultant leaf litter was distinct between age groupings whereby young sites exhibited the greatest change in chemical character as extractable lignin increased and SFA decreased yielding a cutin-poor residue. Only minor changes to biopolymer character were observed in older sites with residues exhibiting small but opposite trends to the young sites. Decayed wood residues were less dramatically altered in composition and mass yields of lignin and SFA than observed in the leaf amendments. The old forest residues, however, were relatively enriched in SFA with respect to the young sites driven by small changes to both lignin and SFA contents. These patterns in litter decay are consistent with the relatively higher activity of both phenol oxidase and B-glucosidase (enzymes involved in lignin and cellulose decay) in the young forest soil (0-5 cm) plots. We are currently assessing if these litter decay dynamics are manifest in the chemical nature of the light and heavy particulate organic matter in the associated soils.