Localized basal area affects soil respiration temperature sensitivity in a coastal deciduous forest

Pennington, Stephanie C.; McDowell, Nate G.; Megonigal, J. Patrick; Stegen, James C.; Bond-Lamberty, Ben

doi:https://doi.org/10.5194/bg-17-771-2020

Articles | Volume 17, issue 3

https://doi.org/10.5194/bg-17-771-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

https://doi.org/10.5194/bg-17-771-2020

© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 17, issue 3

Research article

|

14 Feb 2020

Research article |

| 14 Feb 2020

Localized basal area affects soil respiration temperature sensitivity in a coastal deciduous forest

Stephanie C. Pennington, Nate G. McDowell, J. Patrick Megonigal, James C. Stegen, and Ben Bond-Lamberty

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Final revised paper (published on 14 Feb 2020)
Supplement to the final revised paper
Preprint (discussion started on 02 Jul 2019)

Interactive discussion

Status: closed

AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

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- Supplement

RC1: 'Comments', Anonymous Referee #1, 24 Jul 2019
- AC1: 'Author Reply to R1', Stephanie Pennington, 12 Sep 2019
RC2: 'Review', Anonymous Referee #2, 26 Jul 2019
- AC2: 'Author Reply to R2', Stephanie Pennington, 12 Sep 2019
RC3: 'Review of Pennington et al 2019', Anonymous Referee #3, 15 Aug 2019
- AC3: 'Author Reply to R3', Stephanie Pennington, 12 Sep 2019

Peer-review completion

AR: Author's response | RR: Referee report | ED: Editor decision

ED: Reconsider after major revisions (18 Sep 2019) by Michael Weintraub

AR by Stephanie Pennington on behalf of the Authors (30 Oct 2019) Author's response Manuscript

ED: Referee Nomination & Report Request started (18 Nov 2019) by Michael Weintraub

RR by Anonymous Referee #1 (22 Nov 2019)

RR by Anonymous Referee #3 (02 Dec 2019)

Suggestions for revision or reasons for rejection

Pennington et al. have provided a nice revision of their original manuscript, which successfully addresses my concerns except for these relatively minor issues:

- I was sorry to see that some version of the figure from the authors’ “OVERALL RESPONSE TO R3” did not make it into the revised draft. I found it helpful for understanding how BA5 might impact Rs via T without having a statistically significant effect on Rs directly. However, if the authors and editor do not feel the need for such a figure, then I do not object.

- lines 57 ff.: The phrasing of this paragraph (particularly the first and last sentences) portrays the influence of vegetation distribution on Rs as a hypothesis to be tested, whereas the citations show that root respiration has already been shown to contribute substantially to Rs, and Rs has already been shown to be higher near tree stems — i.e. the spatial distribution of vegetation has already been shown to affect the spatial distribution of Rs. Additionally, the logic of the first sentence is flawed: the fact that “[a]t large scales, Rs differs between vegetation types and biomes” does not even imply that vegetation type affects Rs (it could be that soil type or other factors affect both vegetation type and Rs), let alone “that the spatial distribution of vegetation might strongly affect Rs via plant root respiration” (which involves logical leaps to spatial distribution and root respiration). This is the paragraph that needs to clearly lay out what’s already known about the influence of vegetation on Rs and state the knowledge gap that this study is going to fill, which is not really about the spatial distribution of Rs, but rather about how vegetation affects the response of Rs to environmental drivers (especially temperature).

- lines 111-114: Soil moisture and temperature measurements don’t belong in a section called “Soil respiration measurements”.

- line 116: Strictly speaking, these are not “tree proximity measurements”, but rather local basal area measurements.

- line 132: I acknowledge the author’s response regarding heteroscedasticity and the logarithm, but I think “ensure homoscedasticity” is too strong language here. I would say that taking the logarithm dampens heteroscedasticity.

- line 134: I think this “equation” requires a bit of justification/derivation. E.g. why SM and SM^2? Does this notation mean that log(Rs) is taken to be linearly related to T5*BA5 and to T20*BA5 but quadratically related to SM? Why?

- line 297 ff.: The conclusion is awkward. Mention of Rs is left out of the first sentence, about the key finding. In the second sentence, “these sites” is ambiguous as to whether you’re referring to all your study sites or just the sites with high BA5. In the third sentence, the fact that “soil respiration at this site [is] highly dynamic and variable” is a direct observation, not something suggested by the findings.

- Fig. 3: The inset adds no information and should be removed. The color scale could be put in its place instead, reduce the overall space required by the figure.

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ED: Publish subject to minor revisions (review by editor) (18 Dec 2019) by Michael Weintraub

AR by Stephanie Pennington on behalf of the Authors (31 Dec 2019) Author's response

ED: Publish as is (10 Jan 2020) by Michael Weintraub

AR by Stephanie Pennington on behalf of the Authors (20 Jan 2020)

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Short summary

Soil respiration (R_s) 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 local basal area (tree area) on R_s in a coastal forest in eastern Maryland, USA. R_s measurements were taken as well as distance from 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.