the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 22 Nov 2024
Technical note: a Weighing Forest Floor Grid-Lysimeter
Abstract. The forest floor (FF) is dominated by plant litter and its decomposition products, thereby it differs significantly from the mineral soil. Because of its wider range of pore sizes and overall high porosity, it has a large capacity to retain water and thus plays an important role in redistributing water to the mineral soil beneath. Until now most studies have focused on the behaviour of the organic layer when wetted and dried in a laboratory setting. Alternatively, field fresh samples were collected to determine the water storage potential. We present a novel low-cost grid-lysimeter designed specifically for the FF, but also suitable for other organic soil layers. It can continuously measure all water balance components of the FF. The lysimeter detects precipitation with an accuracy of 0.03 mm outperforming most rain gauges. The developed setup allows for further customization of in-situ water quality measurements. This technical note describes the setup of the lysimeter and presents performance metrics from laboratory results and initial field data.
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RC1: 'Comment on egusphere-2024-3503', Anonymous Referee #1, 27 Nov 2024
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I enjoyed this simple paper describing an innovative way to measure fine-scale fluxes of water in the forest floor. The presentation was generally clear and I can find no fault with the description of the device or the demonstration of its capabilities. I have some suggestions to improve the presentation in a few instances.
"weighted” lysimeter appears several times where "weighing” lysimeter is meant.
L84 what is an SDI-12 sensor?
Sec 2.2.2 many of these comparisons to alternatives are not very helpful, given that they mainly refer to old hardware. An eye to making the description of the device more timeless would improve its long-term utility.
Sec 2.3 I think the precision and resolution of the load cells is more important than accuracy. Please explain how precisely changes in mass can be resolved. Also I am curious about temperature dependence.
L145 a narrow hole may prevent calibration problems with the bucket, but it does degrade the ability of the device to precisely estimate time of infiltration. That is worth mentioning, along with any information you might have to quantify this effect.
L150 can you give some indication of the morphology of the forest floor? Is this a mor humus with a distinct organic-mineral transition, or a mull humus where the transition is indistinct? I don't think this matters much for the description of the device, but it does give some context on what is possible using this measurement technique.
L152 what is garden fleece?
Figure 3 would improve if it included indications of the reference masses
L214 I don't understand this sentence. It sounds like the second thing is a consequence of the first, and that they are not two separate effects.
L218 I don't understand this sentence. Perhaps fumigation is the wrong word?
Figures 4 and 5 would improve if the width of the time bins was specified.
Instead of SCE and SCM, which are difficult to remember, why not "crown edge" and "crown middle" in all figures? There is plenty of room available.
Table 2 what is 16.5.-26.5.?
Throughout the results: in a few places there are explanations for various things like why percept throughfall varied (L241, L267), but these are not reliable conclusions due to low sample size.
Editing:
In general the English was understandable but awkward in many places. A general for wording would help.
L79 L157 "electronics were"
L144 "has to pass through"
L178 is a sentence fragment
L187 "an influence"
L227, L230 commas where periods are required
Citation: https://doi.org/10.5194/egusphere-2024-3503-RC1 -
RC2: 'Comment on egusphere-2024-3503', Anonymous Referee #2, 20 Dec 2024
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The technical note “A Weighing Forest Floor Grid-Lysimeter” by Paulsen and Weiler reports the technical details, performance tests and preliminary analyses of a novel lysimeter that allows estimating the water storage and retention capacity of the forest floor. The technical innovation is highly appreciated, a lot of work must have been gone in the development of the lysimeters. However, the manuscript sometimes is a little hard to follow i.e., when it’s not clear what pointers refer to, some sentences could be rephrased to make them shorter and clearer. I’d like to suggest some edits that might help to improve the manuscript, but please thoroughly edit the entire manuscript to improve the overall readability. Figure captions are often very short and lack important information, maybe you can improve them during revision.
Overall I only identified one critical aspect that is related to the accuracy of load cells. Most (cheaper) load cells suffer from uncertainty with changing temperatures (as the authors also acknowledge) and additionally they have weak long term stability in the measured weight (drift). Did you do any long term reliability testing (ideally with different temperatures) and could you show these results (e.g., in the supplement)? I understand that new measurements and tests might not be an option, so therefore I’d suggest to at least discuss this topic thoroughly and report the metrics provided by the load cell supplier in the manuscript. Maybe a paragraph can be added in the discussion.
L17: induce runoff generation? Should this be “reduce”?
L 19-20: rephrase the sentence: I do not think that these are “ecosystem services” of canopies, but you rather want to state that similar processes occur in canopies & FF, also I’d rephrase the processes: e.g., retention (is important but missing currently), water redistribution (I think this is meant by water infiltration) - > maybe more general: canopies and FF affect the temporal, spatial distribution but also chemical composition of soil water recharge.
L 28: change a to the
L 39: not clear what “true” precipitation is
L 65: remove: “without further securing measures” -> not clear what it means to me.
L 68: into
L 69: remove “later”
L 79: were instead of was
L84: rephrase: the output data from the FFGL are in SDI-12
L 102: I’d say “testing” instead
L 179: make this a correct sentence
L 182: filled instead of loaded
L 185 (& 193): remove “in”
L 201: yield instead of yielding
L 215: () missing
L 220: I’d say “approximately” here
Figure 4: water flux in mm / per time, write out precipitation and drainage in the legend, better call it “cumulative water amounts”
Figure 5: mention in the caption which lysimeter is below the edge (SCE) vs. the middle of the canopy (SCM)
Table 2: it would be good to reiterate the abbreviations in the caption
L263: say “Evaporation”
Figure 6, caption: why are some words capitalized? better call it “cumulative water amounts”, not clear what “measured on the tower” means, say above the canopy?
L 267: remove “up”
L 271: could & could, maybe this sentence can be rephrased
Figure 7: make clear what the two lysimeters are (i.e., mention below the edge (SCE) vs. the middle of the canopy (SCM))
L 276:say with SMT100 sensors, upslope “of” the lysimeter
L 277: how is this 5mm to 10% conversion done?
Figure 8: also here the Figure caption lacks some information
L 285 – 287: The sentence doesn’t make sense to me. i.e., I’d start with “The data include…” but it’s not clear how the lysimeter data include information on climate conditions, canopy structure; “e”vaporation -> now I understand, etc. misses a second dot, still not very clear.
L 291: measurement noise
L 298: of total drainage
L 314: not clear what that means
The “conclusions & outlook” are only an outlook, maybe you can rewrite this
Citation: https://doi.org/10.5194/egusphere-2024-3503-RC2
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