PARENT SESSION
Contributed Oral Session 146: Biogeochemistry: Nutrient Dynamics; Carbon Sequestration
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 524 C, Level 5, Palais des congrès de Montréal
Iron and aluminum effects on oxalate regulation and subsequent base cation accumulation during wood decomposition by brown-rot fungi.
Schilling, Jonathan*,1, Jellison, Jody1, Shortle, Walter2, 1 University of Maine, Orono, ME2 USDA Forest Service, Durham, NH
ABSTRACT- Brown-rot fungi are the primary agents of softwood decomposition in northern coniferous forests. These fungi are theorized to translocate and complex soil-derived base cations during wood decay. Base cation immobilization reduces stochastic leaching and helps conserve soil buffering capacity, a valuable function in acid-sensitive northern spodosol soils. In collaboration with the USDA Forest Service, we are using inductively-coupled plasma spectroscopy (ICP) to monitor cation dynamics in decaying boles from four tree species at two northeastern forest sites. Over the past 8 years using a repeated measures design, we have observed a volume-based enrichment in wood calcium (Ca) similar to results inferred from chronosequence data. We have also demonstrated using SEM and x-ray microanalysis that translocated Ca often crystallizes with oxalate produced by decay fungi. Although oxalate has been characterized as a metabolic by-product in high C:N wood, recent biochemical studies suggest that accumulating oxalate in wood could interfere with iron reduction, a prerequisite for brown-rot decay. To test fungal oxalate regulation and relevant soil metal effects, we pre-treated spruce wood blocks with 0, 1, 10, and 100 mM sodium oxalate and incubated the wood for 12 weeks on non-amended and metal-amended agar inoculated with Fomitopsis pinicola and Meruliporia incrassate. We used HPLC to quantify oxalate in week-12 wood and found that on non-amended agar, wood oxalate had been equalized to a final level similar to the 1 mM control. Wood decayed by both fungi on agar amended with Fe and aluminum (Al), however, showed significantly enhanced oxalate production. Notably, only Fe enhanced the wood decay rate, an observation consistent with Fenton-based brown-rot theory. We are currently studying the effects of amorphous Fe-hydroxide and Al-hydroxide on oxalate regulation and the potential correlation between soil Fe availability and Ca accumulation during wood decomposition.
Key words: fungi, oxalic acid, acid neutralizing capacity (ANC), wood decay