Leaf-Scale Study of Biogenic Volatile Organic Compound Emissions from Willow (Salix spp.) Short Rotation Coppices Covering Two Growing Seasons
Round 1
Reviewer 1 Report
Minor corrections are required:
Table 2. 2016. Relative canopy height…Line 5: put ; instead of :
Part 2.4: It is better to put spaces before and after formulas.
Fig.1 and 2: It is not possible to understand the emission rate levels of SQTs, MTs and other VOCs.
Table 4 and 5: after Bottom… “Average” is possibly should be lowercased.
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Reviewer 2 Report
The manuscript presents the BVOC emissions of a Swedish managed willow varieties growing as bio-energy crops. Calculated the average BVOCs emission rate for different temperatures, photosynthetically active radiation (PAR) and canopy height. The sampling lasted 16 months (July 2015 - October 2016) so we cannot report a long-term study. The title should be changed. The number of samples is satisfactory. The data is rather old.
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Reviewer 3 Report
Paper examines the emissions from Salix species, which is likely to expand due to demand on fast-growing wood. Paper is well written (maybe too long) with important findings derived from leaf chamber measurements and thermal desorption. Unfortunatelly not all important and highly abundant compounds were not detectable (methanol, short chain oxygenated VOC etc). Nevertheless, the paper gives an overview of the Salix species for potential to emit various BVOCs.
Here are soem specific comments, after adressing them, the paper could be published.
Why there are not numbered lines? I indicate only pages then.
Page 2: it is nit true, that under high NOx there is production of O3, it depends on the ratio VOC/NOx. Please change
Page 2: tropospheric O3 and its impacts does not solely depend on its concentration, but on the real flux to plant stomata, which are mostly being closed when the concentration is too high. See paper (10.17221/129/2019-JFS) which you might cite here.
Table 3: you have detected no oxidation products of monoterpenes and isoprene? (MVK, MEK, pinanaldehydes, acetone, acetaldehydes)?
page 20: please indicate exactly how much of assimilated carbon has been released back in form of BVOCs in our case. Moreover, see paper 10.1016/j.agrformet.2016.10.005 where there is report of usually 0.5% of C released back in form of VOCs with maxima reaching 1.5% with methanol occupying 25% from the percentage (which you did not measured unfortunately)
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Reviewer 4 Report
Review: Long-Term Leaf-Scale Study of Biogenic Volatile Organic Compound Emissions from Willow (Salix spp.) Short Sotation Coppices by Karlsson et al.
Summary and overall recommendation:
This manuscript describes a comprehensive field work and aims to characterize BVOC emissions from Salix trees during 2015-2016. They determined seasonal trends in emission rates and spectra and assess the differences between leaves growing at different heights within the canopy. The authors further quantified the standardized emission rates from all the BVOC groups, and subsequent discussions and implications were presented.
As far as I know, quantifying BVOC within leaf scales with long-term and high-precision is not an easy work due to their complex chemical nature, and it requires strong measuring techniques and good QA/QC. Thus, a detailed characterization of BVOC is important, and the authors provided temperature and light (PAR) dependence of BVOC emissions, which are quite useful for modelling. It may provide further implication on our understanding of gas-phase oxidation and SOA formation in similar forested environments, particularly within the atmospheric community. This paper is well written and the whole work appears technically sound, and the topic is novel and of broad interest to the audience of Atmosphere. Thus, I recommend publication with a minor revision after addressing the below comments.
Comments:
- The authors mentioned “emissions of other VOCs were lower from the upper part of the canopy”. Are these other VOCs referring to the end part of Table 3 ? Why these VOCs have different behavior (regarding to canopy position of leaves) than isoprene/MTs/SQTs? Since these other VOCs are mostly OVOCs (e.g. aldehyde and organic acids), I wonder these other VOCs are really from tree emissions. Is that could be from ambient background, or oxidation products of these well-known BVOC species like isoprene/MTs/SQTs ?
- How is the measured and standardized emission rates from this study compared to those reported in the previous literatures? The authors may consider to add a summary table that including different situations with previous work, which may highlight the difference and similarity.
- Why using two approaches (e.g. branch chamber and leaf chamber) to quantify BVOC? What are the purposes, difference, advantage or disadvantage for both methods?
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Round 2
Reviewer 2 Report
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