Organic matter composition and dynamics in a northern hardwood forest ecosystem 15 years after clear-cutting

David A N Ussiri, Chris E Johnson

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36 Scopus citations

Abstract

Soil organic matter (SOM) plays an important role in governing soil properties and nutrient cycling in forest ecosystems. Clear-cutting alters the SOM cycle by changing decomposition rates and organic matter (OM) inputs to the forest ecosystem. We studied the 15-year clear-cutting response on the properties and composition of SOM at the Hubbard Brook Experimental Forest (HBEF) in New Hampshire. Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy was used to study the structural chemistry of SOM in whole soils and extracted humic substances. Overall, alkyl C and O-alkyl C were the dominant C fractions in soils and humic substances. Alkyl C accounted for 38-49% of the total NMR signal intensity in soils and 33-56% in humic substances. O-alkyl C accounted for 32-45% of the signal intensity in soils and 20-31% in humic substances. Following clear-cutting, the contribution of O-alkyl C increased in whole soils and humic acids of the Oa horizon, while alkyl C decreased in whole soils and humic acids of Oa and Bh horizons. Thus, the ratio of alkyl C to O-alkyl C, an index of the degree of decomposition of SOM, decreased in whole soils and humic acids after clear-cutting, indicating that the SOM in post-harvest soils is less decomposed relative to pre-harvest soils. On average, humic substances accounted for 47% of SOM. The concentration of humic acid decreased by up to 25% in Oa, E and Bh horizons after clear-cutting, while the concentration of fulvic acid decreased by more than 40% in the Oa and E horizons. Together, these results indicate that clear-cutting resulted in the loss of humic substances from the forest floor and upper mineral horizons, which was replaced by less decomposed OM in the post-clear-cut soils under the regrowing forest.

Original languageEnglish (US)
Pages (from-to)131-142
Number of pages12
JournalForest Ecology and Management
Volume240
Issue number1-3
DOIs
StatePublished - Mar 15 2007

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Keywords

  • C CPMAS NMR
  • Forest clear-cutting
  • Forest soils
  • Hubbard Brook Experimental Forest
  • Humic substances
  • Spodosol

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Forestry
  • Ecology

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