HR: 0800h
AN: B41C-0647    [Abstracts]
TI: Biochemical Control of Fungal Biomass and Enzyme Production During Native Hawaiian Litter Degradation
AU: * Amatangelo, K L
EM: kamatang@stanford.edu
AF: Stanford University, Department of Biological Sciences, Stanford, CA 94309,
AU: Cordova, T P
EM: cordovap@stanford.edu
AF: Stanford University, Department of Biological Sciences, Stanford, CA 94309,
AU: Vitousek, P M
EM: vitousek@stanford.edu
AF: Stanford University, Department of Biological Sciences, Stanford, CA 94309,
AB: Microbial growth and enzyme production during decomposition is controlled by the availability of carbon substrates, essential elements, and the ratios of these (such as lignin:N). We manipulated carbon:nutrient stoichiometry during decomposition using a natural fertility gradient in Hawaii and litter of varying initial biochemistry. We collected freshly senesced litter of seven biochemically distinct species from three sites offering differing levels of N, P, cations, and ¹⁵N , but similar yearly rainfall and temperature patterns. Litter types were decomposed at both the sites they were collected, and at the other site(s) that species was found. Litter was collected at multiple time points, and after one year of decomposition, calculated K constants varied an order of magnitude, from 0.276 to 2.76. Decomposition rates varied significantly with both litter site of origin and deployment, except at the oldest, P-limited site, where litter site of origin was not significantly correlated with decomposition within species. As microbial exocellular enzymes provide the catalyst for the breakdown of organic molecules including phenols, cellulose, and cutin, we assayed polyphenol oxidase, cellobiohydrolase, cutinase, chitinase, and lignin peroxidase to evaluate the breakdown sequence of different litter types. To measure the fungal biomass accumulating during decomposition, we extracted (22E)-Ergosta-5,7,22-trien-3beta- ol (ergosterol) on a subset of samples. The production of particular exocellular enzymes on litter species responded distinctly to origin and decomposition sites: after six months, chitinase and cellobiohydrolase were significantly affected by origin site, whereas polyphenol oxidase activity was controlled by deployment site. We conclude that site characteristics can alter the interaction between litter carbon:nutrient ratios and decomposition rate, mediated through microbial biomass and enzyme production.
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting