Title: Seasonal changes in the chemical quality and biodegradability of dissolved organic matter exported from soils to streams in coastal temperate rainforest watersheds
Author: Fellman, Jason B.; Hood, Eran; D'Amore, David V.; Edwards, Richard T.; White, Dan
Source: Biogeochemistry. 95: 277-293
Description: The composition and biodegradability of streamwater dissolved organic matter (DOM) varies with source material and degree of transformation. We combined PARAFAC modeling of fluorescence excitation-emission spectroscopy and biodegradable dissolved organic carbon (BDOC) incubations to investigate seasonal changes in the lability of DOM along a soil-stream continuum in three soil types: bog, forested wetland and upland forest. The percentage of BDOC ranged from 7 to 38 across all sites, and was significantly greater in soil compared to streamwater in the bog and forested wetland, but not in the upland forest. The BDOC also varied significantly over the entire sampling period in soil and streamwater for the bog and forested wetland, as BDOC peaked during the spring runoff and was lowest during the summer months. Moreover, the chemical quality of DOM in wetland soil and streamwater was similar during the spring runoff and fall wet season, as demonstrated by the similar contribution of protein-like fluorescence (sum of tyrosine and tryptophan fluorescence) in soil water and in streams. These findings suggest that the tight coupling between terrestrial and aquatic ecosystems is responsible for the delivery of labile DOM from wetland soils to streams. The contribution of protein-like fluorescence was significantly correlated with BDOC (p < 0.001) over the entire sampling period indicating DOM is an important source of carbon (C) and nitrogen (N) for heterotrophic microbes. Taken together, our findings suggest that the production of protein-rich, labile DOM and subsequent loss in stream runoff might be an important loss of labile C and N from coastal temperate watersheds.
Keywords: biodegradable dissolved organic carbon, dissolved organic matter, dissolved organic nitrogen, fluorescence, PARAFAC, peatland, biogeochemistry
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Fellman, J.B.; Hood, E.; D'Amore, D.V.; Edwards, R.T.; White, D. 2009. Seasonal changes in the chemical quality and biodegradability of dissolved organic matter exported from soils to streams in coastal temperate rainforest watersheds. Biogeochemistry. 95: 277-293.
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