Fluorescence characteristics and biodegradability of dissolved organic matter in forest and wetland soils from coastal temperate watersheds in southeast Alaska

Abstract

Understanding how the concentration and chemical quality of dissolved organic matter (DOM) varies in soils is critical because DOM influences an array of biological, chemical, and physical processes. We used PARAFAC modeling of excitation-emission fluorescence spectroscopy, specific UV absorbance (SUVA₂₅₄) and biodegradable dissolved organic carbon (BDOC) incubations to investigate the chemical quality of DOM in soil water collected from 25 cm piezometers in four wetland and forest soils: bog, forested wetland, fen, and upland forest. There were significant differences in soil solution concentrations of dissolved organic carbon (C), nitrogen (N), and phosphorus (P), DOC:DON ratios, SUVA₂₅₄ and BDOC among the four soil types. Throughout the sampling period, average DOC concentrations in the four soil types ranged from 9 to 32 mg C/L, and between 23 and 42 percent of the DOC was biodegradable. Seasonal patterns in dissolved nutrient concentrations and BDOC were observed in the three wetland types suggesting strong biotic controls over DOM concentrations in wetland soils. PARAFAC modeling of excitation-emission fluorescence spectroscopy showed that protein-like fluorescence was positively correlated (r² = 0.82; P < 0.001) with BDOC for all soil types taken together. This finding indicates that PARAFAC modeling may substantially improve the ability to predict BDOC in natural environments. Coincident measurements of DOM concentrations and BDOC and PARAFAC modeling confirmed that the four soil types contain DOM with distinct chemical properties and have unique fluorescent fingerprints. DOM inputs to streams from the four soil types therefore have the potential to alter stream biogeochemical processes differently by influencing temporal patterns in stream heterotrophic productivity.

Keywords

Biodegradable dissolved organic carbon, dissolved organic matter, fluorescence, PARAFAC, peatland, soil biogeochemistry

Citation

Fellman, Jason B.; D'Amore, David V.; Hood, Eran; Boone, Richard D. 2008. Fluorescence characteristics and biodegradability of dissolved organic matter in forest and wetland soils from coastal temperate watersheds in southeast Alaska. Biogeochemistry. 88(2): 169-184