| 05 Dec 2025
Seasonal dynamics of vegetation effect on peatland surface energy balance
Abstract. Peatland ecosystems play a major role in regulating the climate by storing carbon and modulating surface energy fluxes. While energy fluxes in these ecosystems are strongly influenced by climate conditions, separating the influence of climate and vegetation remains challenging. Here, we analyse eddy covariance measurements collected in 2023 at a degraded raised bog in northwest Germany. Using high-frequency gas flux and meteorological observation data we (1) characterize the annual and seasonal dynamics of radiative and turbulent energy fluxes, (2) quantify the climatic and biotic (i.e., stomatal regulation) controls on latent heat flux (LE), and (3) identify the periods d when vegetation becomes a weaker driver of LE due to stomatal regulation.
To assess the biotic controls on latent heat flux (LE), we examined the role of canopy stomatal conductance and vegetation gross primary productivity (GPP). Canopy conductance (gc) was estimated using the inverted Penman–Monteith equation, which allowed us to model a continuous time series of gc. Abiotic drivers of energy fluxes were evaluated by analysing daily and seasonal patterns of radiation, air temperature, vapor pressure deficit (VPD), and water table depth (WTD). The relative effect sizes of biotic and abiotic drivers were quantified using generalized least squares with autoregressive errors (GLSAR). Our results show that mean daily LE peaks ranged from 8.5 to 215 W m⁻² in 2023, with seasonal variations in vegetation productivity exerting a strong influence. GPP, VPD, and net radiation emerged as the dominant drivers of LE dynamics, while no relationship with WTD was observed. These findings highlight that both GPP and VPD must be jointly considered in analyses of turbulent energy fluxes, as their interactions exert nonlinear effects on ecosystem–atmosphere exchange of energy.
General comments
The manuscript “Seasonal dynamics of vegetation effect on peatland surface energy
balance" by Flemming et al. report energy fluxes and look into their drivers at a restored peatland using 1 year of eddy covariance data. Despite the topic is interesting, the manuscript is very poorly written with confusing justification on hypotheses, weak analyses to support tests of hypotheses, and messy abstract, introduction, and discussion. Additionally, the results are quite trivial that radiation is the most important driver of LE and VPD can additionally exert impacts on LE via biotic controls are very well known. Furthermore, there’s no discussions on limitations of analyses while the authors only used 1 year of data and didn’t consider lagging effects. I am afraid to say the manuscript has many fundamental issues that the authors have to address. I was not able to finish reading the entire manuscript because all the confusions from the fundamental parts. I strongly encourage the authors to put substantial efforts into refining the manuscript to make it matching the quality of Biogeosciences. Here are my major comments:
[Major comments]
1.Abstract is not well written
As the first piece to be seen for a manuscript, a nicely constructed abstract is critical. However, the current iteration has many errors and confusing spots that make it difficult for readers to get the importance of this study.
- The goal of this study is not clear. The authors said “energy fluxes in these ecosystems are strongly influenced by climate conditions” but wanted to “separate the influence of climate and vegetation remains challenging”. If it’s strongly influenced by climate conditions, why is it necessary to separate vegetation effects?
- Linked to the previous point, by saying only GLSAR, it’s unclear how it can do the separation.
- I can’t follow the justification of jumping from surface energy fluxes to LE, how about sensible heat flux (H)? Isn’t vegetation also affecting H, e.g., leaf wetness, structure (subjecting to what species), etc? And how can you claim both GPP and VPD must be jointly considered in analyses of “turbulent energy fluxes” in the end?
- The authors specifically mentioned that abiotic drivers were evaluated using daily
and seasonal patterns; however, not for biotic ones but only saying “continuous time series”.
- How did seasonal variations in vegetation productivity exert a strong influence on mean daily LE (Line 18-19)? And is vegetation productivity here GPP? And what’s the temporal scale of LE dynamics (the end of Line 19) then?
- How did the “nonlinear” effect determine (Line 21)?
- Mix used of present and past tense
2. Similarly, the introduction was not well structured and does not solve issues in the abstract
- The author spent more than 50% of the introduction stressing the importance and drivers of LE, but suddenly said they would investigate energy flux partitioning (Line 53)?
- The entire second paragraph (Line 40-49) contains many pieces of information but no convergence. What is the purpose of saying knowledge gap in Central European then importance of WTD, Rn, VPD, and vegetation?
- Hypotheses (b) and (c) are very confusing. So, if Rn is the most important driver, why is it even necessary to know canopy conductance can have the greatest influence on LE in spring? Readers can get confused, why did you focus on unimportant drivers?
- Where’s the elaboration on importance of separating climate and vegetation control on LE? This is your first sentence in the abstract.
- Gerling et al., (2019) looked into soil moisture and ET but not WTD
3. Weakly linked hypotheses and tests
Ignoring the confusing hypotheses mentioned above, it’s very difficult to find justification of how those analyses in the methods test the hypotheses. Here I put the hypotheses:
(a) LE exceeds H in summer, while the opposite holds in winter, due to higher VPD and active vegetation during the growing season
(b) Rn is the primary driver of LE, as global radiation is the main energy source for the ecosystem
(c) canopy conductance (gc) – and its influence on LE – is greatest in spring, when leaves are fully developed but stomatal regulation is still weak under low VPD conditions.
- The authors first surprisingly added 2 sentences (Line 131-132) on testing VPD control on gc. What’s the purpose? Influence of gc on LE is not confirmed at all.
- In Section 2.6, the final analysis, the authors said they examined the biotic and abiotic variables influencing LE by including Rn, GPP, VPD, Ta and WTD. Then where to test the link of gc to LE? And GPP is the only biotic factor, why spending that many efforts to obtain gc?
4. Messy uses of abbreviations
The authors either defined an abbreviation but not using it consistently or randomly use abbreviations without definitions. Here are some examples, and I don’t think it’s reviewer’s task to do this typesetting, and it’s greatly disrupting my reading.
Line 33: You just acronymized transpiration
Line 56: You’ve defined EC. Check all the following lines (e.g., 74, 76, …)
Line 85: Subscript 2 and what’s GPP?
Table 1: What’s PAR?
Line 98: You’ve defined P
Line 117: You’ve defined evaporation
Line 119: You’ve defined precipitation
….
5. The manuscript was not even finished properly
Why is there only one subsection (4.1) and why aren’t discussions on other hypotheses in independent subsections? Why is the overall conclusion (Line 358-361) ended so casually? And why is it included in subsection 4.1 (Drivers of latent energy)?
6. Missed mentioned limitations
Do you this your findings will stand when another year of data is included? Where could be the limitations? Do you think lagging effects can be significant, why and why not?
[Minor comments]
Line 11: What does d mean here? … the periods “d” when …
Line 24: SOC is not needed, only used once
Line 29-30: This should go with Line 25-26
Line 33: italicize “Betula spp.”
Line 41: What’s LE? Not defined yet in the main text.
Line 144: “two separating the growing season (March 15 to October 15) from the non-growing season” reads very awkwardly. So it’s “2 growing seasons” or “2 seasons with 1 growing season and 1 non-growing season”?