Carbon remineralization in a north Florida swamp forest: Effects of water level on the pathways and rates of soil organic matter decomposition

James D. Happell, Jeffrey P. Chanton

Research output: Contribution to journalArticle

47 Scopus citations

Abstract

Water level controlled gas emissions from North Florida swamp forests. Under flooded conditions, CO2 and CH4 were the principle carbon gases transported to the atmosphere by bubble ebullition and molecular diffusion. The respective emission rates were for CO2, 29.3 ± 16.4 (13% by means of ebullition, 87% by means of diffusion, error is ± 1 standard deviation throughout) and for CH4, 2.16 ± 2.24 (45% by means of ebullition, 55% by means of diffusion) mol m−2 yr−1. Methane emissions were significantly attenuated by CH4 oxidation which occurred primarily at the sediment‐water interface. Forty‐six ± 22 % (n=19) of the belowground CH4 diffusing to this interface was oxidized before it could escape to the atmosphere. Under dry conditions, CO2 was the principle carbon gas released and atmospheric CH4 was consumed by microbes in the soil. The respective rates were 101.2 ± 26.80 and −0.015 ± 0.005 mol mr−2 yr−1. A carbon budget for the degradation of soil organic matter was developed for a swamp forest site under flooded and dry conditions. Assuming that live root respiration accounted for 67% (value determined in a swamp forest and is at the upper range of literature values) of the total CO2 emissions (given above), we calculate that under flooded conditions carbon remineralization proceeded at a total rate of 11.9 mol C m−2 yr−1. Forty‐nine percent of the remineralization was by means of nonmethanogenic processes which produce CO2; the balance was by means of methanogenic processes, which produce both CH4 and CO2. Under dry conditions, remineralization was dominated by aerobic processes at a rate of 33.7 mol C m−2 yr−1. Carbon inputs to the soil occurred by aboveground and belowground production. Aboveground litter production contributed 25.6 mol C m−2 yr−1. If belowground production contributed an equal amount, then over the course of this study organic carbon accumulated in the soils at rates of 39.3 and 17.5 mol C m−2 yr−1 under flooded and dry conditions, respectively. If root respiration accounted for only 6% (lowest value in literature) of the total CO2 emissions, organic carbon would accumulate in the soil at a rate of 21.6 mol C m−2 d−1 under flooded conditions and be lost from the soil at a rate of 43.8 mol C m−2 d−1 under dry conditions.

Original languageEnglish (US)
Pages (from-to)475-490
Number of pages16
JournalGlobal Biogeochemical Cycles
Volume7
Issue number3
DOIs
StatePublished - Sep 1993
Externally publishedYes

ASJC Scopus subject areas

  • Global and Planetary Change
  • Environmental Chemistry
  • Environmental Science(all)
  • Atmospheric Science

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