Dissecting the Effects of Diameter on Wood Decay Emphasizes the Importance of Cross-Stem Conductivity in Fraxinus americana
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Pest outbreaks are driving tree dieback and major influxes of deadwood into forest ecosystems. Understanding how pulses of deadwood impact the climate system requires understanding which factors influence greenhouse gas production during wood decay. Recent analyses identify stem diameter as an important control, but report effects that vary in magnitude and direction. This complexity may reflect interacting effects of soil contact, geometry and variable tissue properties. To dissect these effects, we implemented a three-way factorial experiment in Fraxinus americana, (white ash), an iconic North American species threatened by an invasive beetle. Soil contact accelerated decay rates by an order of magnitude with an effect that varied with stem diameter, not bark presence. After experimentally controlling surface area-to-volume ratio, half-buried wide stems decayed more slowly than half-buried narrow stems but more quickly than the aggregate decay rate of buried and suspended stems. These results closely matched variation in moisture content within and among samples, suggesting that limited vertical conduction of soil moisture through deadwood mediates the effect of stem diameter on wood decay. Soil contact also influenced greenhouse gas concentrations reinforcing recent evidence that deadwood acts as a source for CO2 and CH4 while acting as a sink for N2O. Our results suggest that managing tree species affected by pest outbreaks, including F. americana, for biomass salvage and greenhouse gas mitigation requires understanding traits that mediate wood permeability and diffusivity to soil moisture and greenhouse gases.
Keywordscarbon dioxide forest carbon emerald ash borer methane nitrous oxide wood decay
The authors thank the staff of Tyson Research Center and Washington University in St. Louis for access to the site and for logistical support. In particular, we thank T. Mohrman for his help in safely harvesting the large tree. A. Miller helped with initial deployment. S. Hobbie and two anonymous reviewers provided constructive comments that helped improve an earlier draft of this manuscript. Funding was provided by NSF Grant DEB 1302797 to AEZ and NSF Grant DGE 1405135 to KRC.
- Allen CD, Macalady AK, Chenchouni H, Bachelet D, McDowell N, Vennetier M, Kitzberger T, Rigling A, Breshears DD, Hogg EH. 2010. A Global Overview of Drought and Heat-Induced Tree Mortality Reveals Emerging Climate Change Risks for Forests. Forest Ecology and Management 259:660–84.CrossRefGoogle Scholar
- Bates D, Maechler M, Bolker B, Walker S. 2014. lme4: Linear Mixed-Effects Models Using Eigen and S4. R package version 1.1-7.Google Scholar
- Bretz F, Hothorn T, Westfall P. 2015. Multiple Comparisons Using R. Boca Raton: CRC Press, Taylor & Francis.Google Scholar
- Carll CG, Highley TL. 1999. Decay of Wood and Wood-Based Products Above Ground in Buildings. Jteva 27:150–8.Google Scholar
- Dwason H. 2013. Working Group I Contribution to the IPCC Fifth Assessment Report—Summary for Policymakers. Climate Change 2013: The Physical Science Basis vol 53, p 1–36.Google Scholar
- Klooster WS, Herms DA, Knight KS, Herms CP, McCullough DG, Smith A, Gandhi KJK, Cardina J. 2014. Ash (Fraxinus spp.) Mortality, Regeneration, and Seed Bank Dynamics in Mixed Hardwood Forests Following Invasion by Emerald Ash Borer (Agrilus planipennis). Biological Invasions 16:859–73.CrossRefGoogle Scholar
- Moser WK, Hansen MH, Brand GJ, Treiman TB. 2007. Missouri’s Forest Resources in 2005. USDA General Technical Report NRS-15. St. Paul, MN.Google Scholar
- Pan Y, Birdsey RA, Fang J, Houghton R, Kauppi PE, Kurz WA, Phillips OL, Shvidenko A, Lewis SL, Canadell JG, Ciais P, Jackson RB, Pacala SW, McGuire AD, Piao S, Rautiainen A, Sitch S, Hayes D. 2011. A Large and Persistent Carbon Sink in the World’s Forests. Science 333:988–93.CrossRefPubMedGoogle Scholar
- R Development Core Team. 2010. R: A Language and Environment for Statistical Computing. http://www.r-project.org.
- Taylor AM, Garner BL, Morrell JJ. 2002. Heartwood Formation and Natural Durability—A Review. Wood and Fiber Science 34:587–611.Google Scholar
- Zuo J, Berg MP, Klein R, Nusselder J, Neurink G, Decker O, Hefting MM, Sass-Klaassen U, van Logtestijn RSP, Goudzwaard L, van Hal J, Sterck FJ, Poorter L, Cornelissen JHC. 2016. Faunal Community Consequence of Interspecific Bark Trait Dissimilarity in Early-Stage Decomposing Logs. Functional Ecology 30:1957–66.Google Scholar