Isotopic analysis of respired CO2 during decomposition of separated soil organic matter pools

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dc.citation.epage3291en_US
dc.citation.issue11en_US
dc.citation.spage3279en_US
dc.citation.volume38en_US
dc.contributor.authorCrow, Susan E.
dc.contributor.authorSulzman, Elizabeth W.
dc.contributor.authorRugh, William D.
dc.contributor.authorBowden, Richard D.
dc.contributor.authorLajtha, Kate
dc.contributor.avlauthorBowden, Richard D.
dc.contributor.departmentBiologyen_US
dc.date.accessioned2018-07-02T20:14:12Z
dc.date.available2018-07-02T20:14:12Z
dc.date.issued2006-11-11
dc.description.abstractA detailed understanding of the processes that contribute to the δ13C value of respired CO2 is necessary to make links between the isotopic signature of CO2 efflux from the soil surface and various sources within the soil profile. We used density fractionation to divide soils from two forested sites that are a part of an ongoing detrital manipulation experiment (the Detrital Input and Removal Treatments, or DIRT project) into two soil organic matter pools, each of which contributes differently to total soil CO2 efflux. In both sites, distinct biological pools resulted from density fractionation; however, our results do not always support the concept that the light fraction is readily decomposable whereas the heavy fraction is recalcitrant. In a laboratory incubation following density fractionation we found that cumulative respiration over the course of the incubation period was greater from the light fraction than from the heavy fraction for the deciduous site, while the opposite was true for the coniferous site. Use of stable isotopes yielded insight as to the nature of the density fractions, with the heavy fraction solids from both forests isotopically enriched relative to those of the light fraction. The isotopic signature of respired CO2, however, was more complicated. During incubation of the fractions there was an initial isotopic depletion of the respired CO2 compared to the substrate for both soil fractions from both forests. Over time for both fractions of both soils the respired δ13C reflected more closely the initial substrate value; however, the transition from depleted to enriched respiration relative to substrate occurs at a different stage of decomposition depending on site and substrate recalcitrance. We found a relationship between cumulative respiration during the incubation period and the duration of the transition from isotopically depleted to enriched respiration in the coniferous site but not the deciduous site. Our results suggest that a shift in microbial community or to dead microbial biomass as a substrate could be responsible for the transition in the isotopic signature of respired CO2 during decomposition. It is likely that a combination of organic matter quality and isotopic discrimination by microbes, in addition to differences in microbial community composition, contribute to the isotopic signature of different organic matter fractions. It is apparent that respired δ13CO2 cannot be assumed to be a direct representation of the substrate δ13C. Detailed knowledge of the soil characteristics at a particular site is necessary to interpret relationships between the isotopic values of a substrate and respired CO2.en_US
dc.description.versionPublished articleen_US
dc.identifier.citationCrow, S.E., Sulzman, E.W., Rugh, W.D., Bowden, R.D., and Lajtha, K. (2008). Isotopic analysis of respired CO2 during decomposition of separated soil organic matter pools. Soil Biology & Biochemistry, 38(11): 3279-3291. doi: 10.1016/j.soilbio.2006.04.007en_US
dc.identifier.doi10.1016/j.soilbio.2006.04.007
dc.identifier.issn0038-0717
dc.identifier.urihttp://hdl.handle.net/10456/46609
dc.language.isoen_USen_US
dc.publisherElsevieren_US
dc.relation.ispartofSoil Biology & Biochemistryen_US
dc.relation.isversionofhttps://doi.org/10.1016/j.soilbio.2006.04.007en_US
dc.rightsThis article is published in Soil Biology & Biochemistry (2008) S.E. Crow et al. All rights reserved.en_US
dc.subjectAlfisolen_US
dc.subjectAndisolen_US
dc.subjectConiferous foresten_US
dc.subjectDeciduous foresten_US
dc.subjectδ13Cen_US
dc.subjectDensity separationen_US
dc.subjectIsotopic fractionationen_US
dc.subjectOrganic matteren_US
dc.subjectSoil respirationen_US
dc.titleIsotopic analysis of respired CO2 during decomposition of separated soil organic matter poolsen_US
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