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Biogeosciences An interactive open-access journal of the European Geosciences Union
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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 02 Jan 2019

Research article | 02 Jan 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Spatial changes in soil stable isotopic composition in response to carrion decomposition

Sarah W. Keenan1,a, Sean M. Schaeffer1, and Jennifer M. DeBruyn1 Sarah W. Keenan et al.
  • 1University of Tennessee, Department of Biosystems Engineering and Soil Science, 2506 E.J. Chapman Drive, Knoxville, TN 37996, USA
  • acurrent address: South Dakota School of Mines and Technology, Department of Geology and Geological Engineering, 501 E. St. Joseph Street, Rapid City, SD 57701, USA

Abstract. Decomposition provides a critical mechanism for returning nutrients to the surrounding environment. In terrestrial systems, animal carcass, or carrion, decomposition results in a cascade of biogeochemical changes. Soil microbial communities are stimulated, resulting in transformations of carbon (C) and nitrogen (N) sourced from the decaying carrion soft tissues, changes to soil pH and electrical conductivity as microbial communities release CO2 and mineralize organic N, and significant changes to oxygen availability. Over time, microbial communities transform ammonium to nitrate and potentially N2O through nitrification and denitrification. While many of the rapid changes to soil biogeochemistry observed during carrion decomposition return to background or starting conditions shortly after soft tissues are degraded, some biogeochemical parameters, particularly bulk soil stable δ15N isotopic composition, have the potential to exhibit prolonged perturbations, extending for several years. The goal of this study was to evaluate the lateral and vertical changes to soil stable isotopic composition one year after carrion decomposition in a forest ecosystem. Lateral transects extending 140 cm from three decomposition hotspots were sampled at 20 cm intervals, and subsurface cores were collected beneath each hotspot to a depth of 50 cm. Bulk soil stable isotopic composition (δ15N and δ13C) indicated that one year after complete soft tissue removal and decay, soils were significantly 15N-enriched compared to control soils up to 60 cm from the hotspot center, and enrichment extended to a depth of 10 cm. Our results demonstrate that carrion decomposition has the potential to result in long-term changes to soil biogeochemistry, up to at least one year after soft tissue degradation, and to contribute to bulk soil stable isotopic composition.

Sarah W. Keenan et al.
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Sarah W. Keenan et al.
Sarah W. Keenan et al.
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Short summary
Decaying animals perturb soil biogeochemical cycles. Stable δ15N composition, which reflects the sum of all biogeochemical processes, increases during decay and persists for years. Enrichment following beaver decay persisted after one year, and was evident up to 10 cm depth and 60 cm from the decaying animals, beyond where soils were visibly impacted by decomposition. Nutrients sourced from decaying animals represent an integral and long-lived component of nitrogen cycling in soils.
Decaying animals perturb soil biogeochemical cycles. Stable δ15N composition, which reflects...