Skip to Main Content
Carbon storage in coarse and fine fractions of Pacific Northwest old-growth forest soils.Author(s): P.S. Homann; S.M. Remillard; M.E. Harmon; B.T. Bormann
Source: Soil Sci. Soc. Am. J. 68: 2023-2030
Publication Series: Scientific Journal (JRNL)
PDF: Download Publication (1.1 MB)
DescriptionMany assessments of soil C have been restricted to the <2-mm fraction, but C has recently been identified in >2-mm fractions of forest mineral soils. Our objective was to determine the importance of the >2mm fraction to whole-soil C pools in Pacific Northwest old-growth coniferous forests. Seventy-nine pedons in 18 western Washington and Oregon forests were sampled to a depth of 100 cm. The <2-mm fraction was separated from the >2-mm fraction by airdrying, physically crushing soil, and sieving; C was determined by Leco combustion. The >2-mm fraction contained up to 46% of the whole-soil C and averaged 23% for the seven forests that had C in that fraction. Following treatment with sodium hexametaphosphate to disaggregate soil material, up to 20% of whole-soil C remained in the >2-mm fraction Thus, the >2-mm fraction C appears to be in stable and unstable aggregates, as well as concretions. The whole-soil C in the surface 100 cm of mineral soil ranged from 30 to 400 Mg C ha-1. Multiple regression analysis indicated this C pool was positively related to available water capacity, annual precipitation, and coarse woody debris (r2 = 0.63 to 0.66, n = 18 forests). Similar results were obtained with only the <2-mm soil C, which is the basis of previous regional evaluations. This suggests consideration of the >2-mm fraction does not alter our understanding of the importance of climate and soil texture as controls of soil C pools, but it does affect the quantification of soil C pools in many old-growth forests in the Pacific Northwest.
- Visit PNW's Publication Request Page to request a hard copy of this publication.
- We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
- This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.
CitationHomann, P.S.; Remillard, S.M.; Harmon, M.E.; Bormann, B.T. 2004. Carbon storage in coarse and fine fractions of Pacific Northwest old-growth forest soils. Soil Sci. Soc. Am. J. 68: 2023-2030
- Effects of spatial and temporal climatic variability on terrestrial carbon and water fluxes in the Pacific Northwest, USA
- What the soil reveals: potential total ecosystem C stores of the Pacific Northwest region, USA.
- Soil organic matter fractions in experimental forested watersheds
XML: View XML