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https://doi.org/10.5194/bg-2019-218
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-218
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 02 Jul 2019

Research article | 02 Jul 2019

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

Tree proximity affects soil respiration dynamics in a coastal temperate deciduous forest

Stephanie C. Pennington1, Nate G. McDowell2, J. Patrick Megonigal3, James C. Stegen2, and Ben Bond-Lamberty1 Stephanie C. Pennington et al.
  • 1Joint Global Change Research Institute, Pacific Northwest National Laboratory, 5825 University Research Ct. #3500, College Park, MD 20740, USA
  • 2Pacific Northwest National Laboratory, Biological Sciences Division, Richland, WA, USA
  • 3Smithsonian Environmental Research Center, Edgewater, MD, USA

Abstract. Soil respiration (Rs), the flow of CO2 from the soil surface to the atmosphere, is one of the largest carbon fluxes in the terrestrial biosphere. The spatial variability of Rs is both large and poorly understood, limiting our ability to robustly scale it in time and space. One factor in Rs spatial variability is the autotrophic contribution from plant roots, but it is uncertain how the proximity of plants affects the magnitude and temperature sensitivity of Rs. This study examined the effect of tree proximity on Rs in the growing and dormant seasons, as well as during moisture-limited times, in a temperate, coastal, deciduous forest in eastern Maryland, USA. In a linear mixed-effects model, tree basal area within 5 m (BA5) exerted a significant positive effect on the temperature sensitivity of soil respiration. Soil moisture was the dominant control on Rs during the dry portions of the year while soil moisture, temperature, and BA5 all exerted significant effects on Rs in wetter periods. Our results suggest that autotrophic respiration is more sensitive to temperature than heterotrophic respiration at these sites, although we did not measure these source fluxes directly, and that soil respiration is highly moisture-sensitive, even in a record-rainfall year. The Rs flux magnitudes (0.3–16.6 µmol m−2 s−1) and variability (coefficient of variability 10 %–22 % across plots) observed in this study were comparable to values observed over decades in similar forests. We estimate that four Rs observations were required to be within 50 % of the stand-level mean, and 311 to be within 5 %, at 90 % confidence. A better understanding of the spatial interactions between plants and microbes that results in measured Rs is necessary to link these processes with large scale soil-to-atmosphere C fluxes.

Stephanie C. Pennington et al.
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Stephanie C. Pennington et al.
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Short summary
Soil respiration (Rs) is the flow of CO2 from the soil surface to the atmosphere, and is one of the largest carbon fluxes on land. This study examined the effect of tree proximity on Rs in a coastal forest in eastern Maryland, USA. Rs measurements were taken as well as distance from the soil collar, diameter, and species of each tree within a 15 m radius. We found that trees within 5 m of our sampling points had a positive effect on how sensitive soil respiration was to temperature.
Soil respiration (Rs) is the flow of CO2 from the soil surface to the atmosphere, and is one of...
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