the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Spatial and temporal heterogeneity of soil respiration in a bare-soil Mediterranean olive grove
Abstract. Soil respiration (Rs) is an important carbon flux in terrestrial ecosystems and knowledge about this CO2 release process and the drivers involved is a key topic in the context of global change. However, temporal, and spatial variability has not been extensively studied in semiarid systems such as olive groves. In this study, we show a full year of continuous measurements of Rs with six automatic chambers in a fertirrigated olive grove with bare soil in the Mediterranean accompanied by ecosystem respiration (Reco) obtained using the eddy covariance (EC) technique. To study spatial variability, the automatic chambers were distributed equally under the canopy (Rs Under-Tree) and in the center of the alley (Rs Alley), and the gradient of Rs between both locations was measured in several manual campaigns in addition to azimuthal changes about the center of the olive trees. The results indicate that Rs Under-Tree was three times larger than Rs Alley in the annual computations. Higher Rs was found on the south face, and an exponential decay of Rs was observed until the alley's center was reached. These spatial changes were used to weigh and project Rs to the ecosystem scale, whose annual balance was 1.6–2.3 higher than Reco estimated using EC-derived models. The daytime Reco model performs better the greater the influence of Rs Under-Tree and the night-time Reco model and Rs covaried more the higher the fraction of Rs Alley. We found values of Q10 < 1 in the vicinity of the olive tree and Rs Under-Tree represented 39 % of the Rs of the olive grove. CO2 pulses associated with precipitation events were detected, especially in the alley, during dry periods, and after extended periods without rain, but were not accurately detected by EC-derived models. We point out an interaction between several effects that vary in time and are different under the canopy than in the alleys that the accepted models to estimate Q10 and Reco do not consider. These results show a high spatial and temporal heterogeneity in soil respiration and the factors involved, which must be considered in future work in semi-arid agrosystems.
- Preprint
(2494 KB) - Metadata XML
-
Supplement
(11 KB) - BibTeX
- EndNote
Status: final response (author comments only)
-
RC1: 'Comment on egusphere-2024-848', Anonymous Referee #1, 03 May 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-848/egusphere-2024-848-RC1-supplement.pdf
-
CC1: 'Comment on egusphere-2024-848', Elise Pendall, 14 May 2024
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2024/egusphere-2024-848/egusphere-2024-848-CC1-supplement.pdf
-
RC2: 'Comment on egusphere-2024-848', Kendalynnn Morris, 11 Jul 2024
This article presents one year of soil respiration data from an olive grove with the goal of quantifying spatial, temporal, moisture-driven, and microclimatic variation therein. They upscale their data accordingly and compare it to two different eddy covariance techniques for estimating Reco. This is a solid contribution to the semi-arid carbon cycling literature with a thorough and appropriate treatment of the topic. However, in general, the text leans towards redundancy and could lose substantial length without losing content. This was especially noticeable in the Introduction in the paragraphs beginning L60, L69, and L86 as well as the Discussion, which would benefit from subsections to organize ideas.
L15: azimuthal vs angular vs directional are used throughout the text to refer to this idea, choose one and stick with it
L33: Worth noting here that Rs is composed of both heterotrophic and autotrophic components
L55: Fragment of a sentence
L100: “Arbequina” & “Cortijo Guadiana”, not sure why these are in quotes?
L103: Köppen classification: Csa, is a clearer order for presenting these terms
L123: Here the criteria for determining the best fit should be specified
L126 -126: More information on when gaps occurred would be helpful to the reader, perhaps in the supplement?
L129: I suggest the authors break this into a section on continuous measurements and another on discrete campaigns
L132-133: “the spontaneous seedlings…” this has already been stated in the paragraph above
L139: Missing “a”
L144: This is a little confusing, but readily becomes clear when the values in the supplement are seen. As this table is compact, I suggest including this (or the values in line) in the main text
L228: Fig 3a is referenced, not 3c
L253-255: Error terms should be included here and the associated figure when possible
L264: “…, not being an isolated case” this is awkward phrasing. Suggest “During July, one chamber consistently showed no diurnal variability.” If consistent is too strong, “frequently” could also be used.
L298: “the greatest [increases] in Rs rates” – but also, it is clear the highest magnitude (ie., the greatest) Rs values are at the lowest IEP alleys, these need to be noted.
L319: “began to be found concerning the chamber” this too is awkward, “[relative to] the chamber closest to the tree” is clearer
L325: Link between variable SWC and punctuality of irrigation is not obvious. Perhaps variation in SWC being driven by irrigation is what is meant?
Figure 10: Difficult color scheme for distinguishing the different cardinal directions
L345: ‘in magnitude’ can be removed. Sentence starting “However, although…” this seems contradictory? If they are similar in magnitude, how can they be inverse?
Figure 11: Not sure the right-angle connections are effective here. Lines connecting points should also be the same color as the points to improve readability
L362: It seems highly likely that the differences are largely due to older trees having much larger root systems, this deserves stronger wording than “could be partially explained by”
L369: This explanation is confusingly stated and misses the most likely driver - that there is almost certainly higher %SOC under the tree canopy, so even when moisture conditions are suitable for microbial activity in both microsites, Rh is greater under canopy (see L44 of the intro)
L386: [distance correction] is clearer than “correction distance”
L387/8: arboreal individuals -> trees
L510/1: Rs = heterotrophic and autotrophic respiration, perhaps aboveground respiration and Rs together is meant (ie., Reco from the eddy covariance)
Citation: https://doi.org/10.5194/egusphere-2024-848-RC2
Viewed
HTML | XML | Total | Supplement | BibTeX | EndNote | |
---|---|---|---|---|---|---|
398 | 90 | 23 | 511 | 23 | 14 | 13 |
- HTML: 398
- PDF: 90
- XML: 23
- Total: 511
- Supplement: 23
- BibTeX: 14
- EndNote: 13
Viewed (geographical distribution)
Country | # | Views | % |
---|
Total: | 0 |
HTML: | 0 |
PDF: | 0 |
XML: | 0 |
- 1