Oxalate Biogeochemistry of Forest Soil Ectomycorrhizal Mat Communities

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Drs. Griffiths, Caldwell, Baham and Cromack have shown that certain specialized ectomycorrhizal species of Gautieria and Hysterangium form extensive hyphal or rhizomorph mat structures that are significant features of temperate coniferous forests. In comparison with soils without obvious mat development, both types of mats have elevated pore-water concentrations of dissolved organic carbon, fluoride, oxalate, and sulfate, as well as major and trace metal cations, including Al and Fe which can be responsible for controlling the solubility of both organic and inorganic phosphorus. In Hysterangium mats, most of the oxalate was present in the solid phase, presumably as calcium oxalate, while in Gautieria mats, a relatively larger fraction of oxalate was in solution at concentrations that approached those used in organic matter extractions of soils. While long implicated in mineral dissolution, the ligand properties of oxalate also suggest other significant roles in forest soil processes. Drs. Griffiths, Caldwell, Baham and Cromack will use these mat communities to investigate the role of oxalate species and other major organic ligands in mineral weathering, solution and solid phase soil chemistry, Al and Fe activity, and the processing of organic nitrogen and phosphorus by soil enzymes in diverse forest ecotypes. Results from field studies and laboratory experiments will be used as input to a quasi-steady-state model of soil solution and solid phase biogeochemistry. This model will provide insight into actual mechanisms controlling nutrient cycling in forest ecosystems. These researchers are experts in the area of forest soil biogeochemistry. The facilities available for this research are outstanding.