Tuesday, November 14, 2006

The Use of Spectroscopic Properties as an Indicator of Dissolved Organic Matter Quality in Soils.

Jason Fellman1, David D'Amore2, Eran Hood1, and Rick Edwards2. (1) Univ of Alaska, Fairbanks, AK 99775, (2) USDA Forest Service, Pacific Northwest Research Station, 2770 Sherwood Lane, 2A, Juneau, AK 99801

Organic matter rich soils are a source of carbon and nutrients for growth and cycling in terrestrial ecosystems.  There are substantial fluxes of dissolved organic matter (DOM) from temperate forest soils, although it is generally believed the material that is exported is biologically unavailable after microbial degradation and the cleaving of nutrient-rich portions by soil fauna and plants. Direct measurements of the chemical quality of DOM exported from soils are difficult, although recent advances in fluorescence spectroscopy enable the rapid and precise characterization of aquatic DOM. Despite these recent advances, the use of fluorescence spectroscopy has been applied primarily to marine ecosystems. We measured soil pore water concentrations of DOM as dissolved forms of C, N, and P from 3 distinct soil types: 1) histosol – bog; 2) histosol forested wetland, and 3) spodosol-upland. We also determined the chemical quality of pore water DOM by measuring fluorescence, specific ultraviolet absorbance (SUVA) and biodegradable dissolved organic carbon (BDOC). The use of fluorescence spectroscopy in this study provides a baseline for evaluating how the chemical quality of DOM varies seasonally and within different soil types. Further, this technique is a relatively rapid and inexpensive method for evaluating the chemical quality of soil pore water DOM.