the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 16 Jul 2025
Drivers and CO2 flux budgets in a Sahelian Faidherbia albida agro-silvo-pastoral parkland: Insights from continuous high-frequency soil chamber measurements and Eddy Covariance
Abstract. Agroforestry systems — combining trees with crops and/or livestock — are increasingly promoted as sustainable and climate-resilient land-use strategies. Despite their widespread presence in the Sahel, experimental data on their potential as carbon sinks are scarce. This study presents a full-year, high-frequency dataset of CO2 fluxes in a Sahelian agro-silvo-pastoral parkland dominated by F. albida, located in Senegal’s groundnut basin. CO2 fluxes were continuously measured using automated static chambers, allowing the quantification of soil and crop respiration (Rch), gross primary production (GPPch), and net carbon exchange (FCO2ch) under both full sun and shaded (under tree canopies) environments.
Seasonal patterns of CO2 fluxes were similar in both environments, with peaks during the rainy season. Rch and GPPch were significantly higher under tree canopies, indicating a ‘fertile island’ effect. CO2 flux variability was primarily driven by soil moisture and leaf area index. Chamber-based GPP estimates closely matched those from Eddy Covariance measurements. On an annual scale, F. albida trees contributed approximately 50 % of total ecosystem GPP, with a carbon use efficiency of 0.48. Net annual CO2 exchange was estimated at −1.4 ± 0.02 and −1.8 ± 0.01 Mg C-CO2 ha⁻¹ using chamber and Eddy Covariance methods, respectively. These findings underscore the role of F. albida-based agroforestry systems as effective carbon sinks in Sahelian landscapes, supporting their potential contribution to climate change mitigation.
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Status: open (until 19 Oct 2025)
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RC1: 'Comment on egusphere-2025-2660', Riccardo Picone, 31 Jul 2025
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This work reports a comparison of carbon fluxes between different zones of an agroforestry system during one whole year assessed with two different methodologies. A comparison of the two methodologies was also done. The topic is therefore highly relevant for the journal. The abstract does a good work in framing the context of the study and the relevance of the findings. The introduction effectively presents the topic and its importance, by highlighting key knowledge gaps that will be addressed by the study. Anyway, I would suggest including a brief description of the Eddy Covariance method in this section. In my opinion, the main problem of the paper is that clear starting hypotheses that have driven the work were not stated. This should be addressed. Methodologies appear to be consistent and appropriately described, and all the reported methods have the appropriate bibliographic reference. I would only suggest some minor integrations to the experimental design description. Results are correctly reported in all the necessary detail. The discussion does a very good job in comparing the results to other studies, hypothesizing mechanisms driving the findings, and highlighting limitations of the study. Conclusions realistically summarize the key discoveries. All supplementary materials are relevant and correctly reported. The authors are requested to carefully proofread the “references” section because some journal names are not correctly abbreviated. Based on these considerations, I would recommend minor revisions to be applied to the manuscript before it can be accepted for publication.
Hereafter follow the specific comments I made on the text. Text between quotation marks indicates citations from the manuscript. When multiple lines are indicated, the comments refer either to a full sentence or to a meaningful part of it.
L. 43 Please report the full name of the species when it is first mentioned in the abstract.
L. 57 I would suggest deleting the phrase “of trees”.
L. 64 I would suggest briefly describing the methodology used for this technique.
L. 95 “upscaling” Undertsanding/comprehension?
L. 99 The hypotheses that have driven the study are not stated.
L. 116 I think it is necessary to report the timing of sowing and the crop density.
L. 139 At which distance from the trees were the chambers installed?
L. 147 “half-hour flux measurements” Does this mean that the measurement was repeated every 30 mins in each chamber? If so, I suggest being more clear on this.
L. 160 “indicated” Indicating?
L. 166, 168 “NDVI”, “LAI” Please report the full name.
L. 172-174 How often were VWC and Tsoil measurements repeated?
L.223-227 These two sentences are a repetition.
L. 344 Inside the chambers.
L.351 “references” Reference
L.s 387-388 How do you account for a standard error of the same entity of the measurement itself?
L. 486 “GPPshowed” A space is needed here.
L. 553 “F. albida” Italics is needed here.
L. 617 “roots” Root
L. 634 I suggest deleting these two abbreviations (AF and FS).
L. 683 “have been also” Have also been.
L. 692 “and cowpeas” I do not understand why this is reported here since this crop was not grown during the experimental period.
L. 696 “field's” Field.
L. 710 “footprint's” Footprint.
L. 727 “compartment’s” Compartment.
L. 734 “advancing understanding” Advancing the understanding.
L. 740, 767, 772 “system’s” System.
L. 770, 794, References “F. albida” Italics is needed here.Citation: https://doi.org/10.5194/egusphere-2025-2660-RC1 -
AC1: 'Reply on RC1', Seydina Mohamad Ba, 04 Aug 2025
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We thank the reviewer for their detailed and constructive feedback. All comments will be addressed in the final document, and all the corrections will be made.
Below are our responses to some of the concerns raised.
L. 95 “upscaling” Undertsanding/comprehension?
Thank you for pointing this out.
The main idea, here, is to partitioning the ecosystem fluxes by compartments (soil and trees).
The corrected sentence becomes: “When combined with EC, this dual-method approach strengthens source attribution and improves the partitioning of fluxes across complex agroforestry landscapes”.
L. 139 At which distance from the trees were the chambers installed?
“This was already mentioned in line L.139: at least 20 m from trees”.
L. 147 “half-hour flux measurements” Does this mean that the measurement was repeated every 30 mins in each chamber? If so, I suggest being more clear on this.
This means that a full flux measurement sequences (chamber closure, data acquisition, chamber opening, and purging) takes 30 minutes, before moving on to the next chamber, and so on.
L. 172-174 How often were VWC and Tsoil measurements repeated?
All at 5_min intervals.
L.s. 387-388 How do you account for a standard error of the same entity of the measurement itself?
Here, it refers to the mean ± standard deviation, not the standard error. We have added this clarification in the text.
The sentence now reads: “FS showing (mean ± SD) 0.9 ± 0.9 μmol CO₂ m⁻² s⁻¹ (modeled) and 1.3 ± 1.2 μmol CO₂ m⁻² s⁻¹ (measured)”.
L. 692 “and cowpeas” I do not understand why this is reported here since this crop was not grown during the experimental period.
The field where the EC flux tower is installed features peanut cultivation intercropped with cowpea (L.115). Therefore, the ecosystem respiration fluxes (Reco.EC) measured by the tower include the contribution of cowpea to respiration.
Citation: https://doi.org/10.5194/egusphere-2025-2660-AC1
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AC1: 'Reply on RC1', Seydina Mohamad Ba, 04 Aug 2025
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