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Peer review report 2 On “Biometric and eddy covariance-based assessment of decadal carbon sequestration of a temperate Scots pine forest”
Agricultural and Forest Meteorology 201S (2015) 528–529
Contents lists available at ScienceDirect
Agricultural and Forest Meteorology journal homepage: www.elsevier.com/locate/agrformet
Peer review report
Peer review report 2 On “Biometric and eddy covariance-based assessment of decadal carbon sequestration of a temperate Scots pine forest”
Original Submission Recommendation Minor Revision Comments to Author The paper AGRFORMET-D-12-00151 “Biometric and eddy covariance-based assessment of decadal carbon sequestration of a temperate Scots pine forest.” presents a comparison of carbon sequestration of a Scott pine forest in a temperate maritime climate obtained using two different techniques: eddy covariance and biometry. The paper quantifies carbon sequestration over a 9 year period, analyzes carbon allocation between different ecosystem carbon pools and individual productivity components. The paper is very clear and concise. However I feel the authors could expand a little the results and discussion sessions. For example: - Papers rarely measure the VOC and DOC leaching components of the carbon balance. What is the contribution of these fluxes on the NEPec? what is the error associated with not including these terms in the determination of ecosystem carbon sequestration? - The authors say the NEPsc is uncertain because of uncertainties in the soil measurements. Is fine root production and coarse root measured more easily than soil carbon? - What is the contribution of uncertainty of the different components, and where should studies concentrate more efforts to reduce such uncertainties? - What is the comparison with uncertainties of similar studies? - In the discussion the authors didn’t mention any other studies comparing eddy and biometry. - Also what is the difference between determining NEP estimates on annual or longer temporal interval on this or other studies. I am aware that the term NBP can have different definitions. In general it adds additional term of carbon losses not measured by eddy covariance, ranging from VOC and carbon dissolved in water, to harvest or fires. Some authors apply it to a single ecosystem and annual values, as in this study, some to the “biome” level, a larger
DOI of original article: http://dx.doi.org/10.1016/j.agrformet.2013.02.008. 0168-1923/$ – see front matter http://dx.doi.org/10.1016/j.agrformet.2015.07.200
scale than the single stand. I feel how the NPB term is used in this paper is a bit misleading because it quantifies the biome production of a forest subject to silvicultural practices as thinning and harvest, without including any of these losses. Please consider changing the term NBP, for example following the definition of Chapin 2006. Chapin in his “Reconciling Carbon-cycle Concepts, Terminology, and Methods” paper distinguishes between net ecosystem carbon balance NECB and NBP. NECB is the net rate of C accumulation in (or loss from) ecosystems. Net ecosystem carbon balance differs from NEP when C fluxes other than C fixation and respiration occur. These fluxes include the leaching loss or lateral transfer of C from the ecosystem; the emission of volatile organic C, methane, and carbon monoxide; and the release of soot and CO2 from fire. NBP is the spatial and temporal average of NECB over a heterogeneous landscape. Some additional comments: Research highlights: 3rd point delete “of” Introduction: Line 87: I think the sentence is clearer without the term aboveground. Line 102: As I said earlier, you say NBP should include harvest, and this forest is subject to harvest, but the harvest losses are not included in your NBP estimate. Please consider following Chapin et al terminology and call it NECB. Line 108: sentence not clear Line 111: A lot of published studies quantified annual NEP, and consider it as carbonsequestration. Maybe define the term carbon sequestration is this sentence? Line 118: “relatively high” is vague. Also the random error is not the only error of eddy covariance estimates. There are errors due to the gap-filling, to the use of u*, to gap length. . . The consequences of discarding 55% of the data in this study could be higher than the random error. Line 120: I think uncertainty on sequestration based on C stock as is due to all belowground components, not just soil. Fine and coarse root biomass and productivity, are also highly variable and difficulty to measure. How these uncertainties compare with other studies? Line 128: Curtis 2002, Ehman 2002, C.M. Gough 208 and other studies compare eddy and
Peer review report / Agricultural and Forest Meteorology 201S (2015) 528–529
biometric NEP estimates on a year or multiyear scale. What is so unique about this study? Material and methods: 2.3.3 the coarse root fraction is not mentioned in the belowground biomass paragraphs. What is the difference of SOC and line 261 and Toc in line 292? The diameter of the gouge or the surface area of soil sampled is not reported.
529
2.5 The phytomass and carbon pools carbon analysis data would add important information, many time people just assume it is 50% of dry weight, what is the range and the variability found in the different pools? Line 311: what about the understory PPN? Anonymous Available online 6 August 2015
Contents lists available at ScienceDirect
Agricultural and Forest Meteorology journal homepage: www.elsevier.com/locate/agrformet
Peer review report
Peer review report 2 On “Biometric and eddy covariance-based assessment of decadal carbon sequestration of a temperate Scots pine forest”
Original Submission Recommendation Minor Revision Comments to Author The paper AGRFORMET-D-12-00151 “Biometric and eddy covariance-based assessment of decadal carbon sequestration of a temperate Scots pine forest.” presents a comparison of carbon sequestration of a Scott pine forest in a temperate maritime climate obtained using two different techniques: eddy covariance and biometry. The paper quantifies carbon sequestration over a 9 year period, analyzes carbon allocation between different ecosystem carbon pools and individual productivity components. The paper is very clear and concise. However I feel the authors could expand a little the results and discussion sessions. For example: - Papers rarely measure the VOC and DOC leaching components of the carbon balance. What is the contribution of these fluxes on the NEPec? what is the error associated with not including these terms in the determination of ecosystem carbon sequestration? - The authors say the NEPsc is uncertain because of uncertainties in the soil measurements. Is fine root production and coarse root measured more easily than soil carbon? - What is the contribution of uncertainty of the different components, and where should studies concentrate more efforts to reduce such uncertainties? - What is the comparison with uncertainties of similar studies? - In the discussion the authors didn’t mention any other studies comparing eddy and biometry. - Also what is the difference between determining NEP estimates on annual or longer temporal interval on this or other studies. I am aware that the term NBP can have different definitions. In general it adds additional term of carbon losses not measured by eddy covariance, ranging from VOC and carbon dissolved in water, to harvest or fires. Some authors apply it to a single ecosystem and annual values, as in this study, some to the “biome” level, a larger
DOI of original article: http://dx.doi.org/10.1016/j.agrformet.2013.02.008. 0168-1923/$ – see front matter http://dx.doi.org/10.1016/j.agrformet.2015.07.200
scale than the single stand. I feel how the NPB term is used in this paper is a bit misleading because it quantifies the biome production of a forest subject to silvicultural practices as thinning and harvest, without including any of these losses. Please consider changing the term NBP, for example following the definition of Chapin 2006. Chapin in his “Reconciling Carbon-cycle Concepts, Terminology, and Methods” paper distinguishes between net ecosystem carbon balance NECB and NBP. NECB is the net rate of C accumulation in (or loss from) ecosystems. Net ecosystem carbon balance differs from NEP when C fluxes other than C fixation and respiration occur. These fluxes include the leaching loss or lateral transfer of C from the ecosystem; the emission of volatile organic C, methane, and carbon monoxide; and the release of soot and CO2 from fire. NBP is the spatial and temporal average of NECB over a heterogeneous landscape. Some additional comments: Research highlights: 3rd point delete “of” Introduction: Line 87: I think the sentence is clearer without the term aboveground. Line 102: As I said earlier, you say NBP should include harvest, and this forest is subject to harvest, but the harvest losses are not included in your NBP estimate. Please consider following Chapin et al terminology and call it NECB. Line 108: sentence not clear Line 111: A lot of published studies quantified annual NEP, and consider it as carbonsequestration. Maybe define the term carbon sequestration is this sentence? Line 118: “relatively high” is vague. Also the random error is not the only error of eddy covariance estimates. There are errors due to the gap-filling, to the use of u*, to gap length. . . The consequences of discarding 55% of the data in this study could be higher than the random error. Line 120: I think uncertainty on sequestration based on C stock as is due to all belowground components, not just soil. Fine and coarse root biomass and productivity, are also highly variable and difficulty to measure. How these uncertainties compare with other studies? Line 128: Curtis 2002, Ehman 2002, C.M. Gough 208 and other studies compare eddy and
Peer review report / Agricultural and Forest Meteorology 201S (2015) 528–529
biometric NEP estimates on a year or multiyear scale. What is so unique about this study? Material and methods: 2.3.3 the coarse root fraction is not mentioned in the belowground biomass paragraphs. What is the difference of SOC and line 261 and Toc in line 292? The diameter of the gouge or the surface area of soil sampled is not reported.
529
2.5 The phytomass and carbon pools carbon analysis data would add important information, many time people just assume it is 50% of dry weight, what is the range and the variability found in the different pools? Line 311: what about the understory PPN? Anonymous Available online 6 August 2015