Resprouting Control of Ailanthus altissima by Means of Cut and Stump Covering: Experimental Evidence for a Promising Technique

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This work analyses the effect of different stump coverage and sprout cut on tree-of-heaven sapling survival with a practical outreach in the area of nature-friendly regulation of this highly invasive tree species.

There are more issues, which should be addressed.

1. Title: never use the word “preliminary”, labelling your work as incomplete :-)

2. Abstract:

Line 14: Please, check the word order: “…the effect of black covers applied after cutting on resprouting.”

I miss the reason for the three treatments (SL, SH and SPH), which explains also the cause of the covers removal.  Actually, this was unclear for me along the whole text till I read the Discussion.

Line 18: “…growth peak…”

3. Introduction: too long, needs larger concentration on issues related to your experiment and finally explaining what is its expected contribution to the knowledge. Maybe, it would require to move some literature information from the Discussion as well as focus more on the physiology.

4. Material and Methods:

Line 121: Why in 2021-2024? There are growth data only from 2022-2023. Did you produce the plant material in 2021 from seeds? I cannot see this information in the text.

How was the SPH pots irrigated?

Line 177: “…four treatments…”

5. Results: You are presenting data only on the sprout number and biomass. More tables and figures are partly duplicate and could be combined. What about to publish your work as Short communication?

There is no statistical analysis provided in Figures.

I would imagine your functional model a little different (box and arrow based scheme).

Author Response

1. Title: never use the word “preliminary”, labelling your work as incomplete :-)

 “preliminary trial” was replaced with “experimental evidence”.

 

2. Abstract: 

Line 14: Please, check the word order: “…the effect of black covers applied after cutting on resprouting.”

I miss the reason for the three treatments (SL, SH and SPH), which explains also the cause of the covers removal. Actually, this was unclear for me along the whole text till I read the Discussion.

To improve clarity, the first part of the abstract was rewritten as: “Ailanthus altissima is an invasive tree threatening the biodiversity in natural and disturbed habitats of temperate regions primarily because of high resprouting vigor. To test the effect of light exclusion on stem and root sprouting, black covers were applied on the cut stumps of 3-year-old saplings grown in pots. Treatments were: SL, stumps exposed to light; SH, only stumps covered; SPH, the entire pot covered; C, intact control plants.”

 

Line 18: “…growth peak…”

Done

 

3. Introduction: too long, needs larger concentration on issues related to your experiment and finally explaining what is its expected contribution to the knowledge. Maybe, it would require to move some literature information from the Discussion as well as focus more on the physiology.

Some general and redundant statements were removed and some literature with apropriate sentences were moved from the discussion to better introduce our experiment.

In detail, removed sentences were:

Lines 50-52

The production of root sprouts, or suckers, is surely the primary driver of ailanthus rapid colonization in disturbed habitats and is also the most important obstacle to the effectiveness of control measures.

Lines 57-59

…, and on human health or the economy. Though eradication is not feasible because of the consolidated presence of ailanthus in most member States

Lines 74-77

Extensive studies are needed to understand whether the biological control of ailanthus by means of V. nonalfalfae could be used without posing present or future risks for the environment and to evaluate its effect on non-target plant species [9].

Lines 91-93

In addition, treatments applied just before winter dormancy were more effective in young plants, whereas no differences in response to application time were observed in older plants.[15].

We moved from the discussion to introduction the sentence at lines 349-352 “The effect of light on bud activation was not studied in ailanthus, but in Rosa hybrida, a resprouting woody species like ailanthus, light stimulated the synthesis of the hormone gibberellin necessary for bud burst, and bud outgrowth was totally inhibited when decapitated plants were placed in darkness” and the corresponding literature [31,34,35]”. The text was re-arranged as ‘”Factors involved in regulating bud dormancy and apical dominance, such as light, were not studied in ailanthus, but in Rosa hybrida, another resprouting woody species, light stimulated the synthesis of the hormone gibberellin necessary for bud burst, and bud outgrowth was totally inhibited when decapitated plants were placed in darkness [34–35].”

Citations were re-numbered according to the new order throughout the text.

 

4. Material and Methods: 

Line 121: Why in 2021-2024? There are growth data only from 2022-2023.

Yes, you are right that growth data refer to the growth seasons 2022 and 2023. However, the experimental period lasted more (2021-2024) because the phenological measures were collected from November 2021 to May 2024, as reported in table 1. We amended the text in methods so to make this clearer to the reader.

 

Did you produce the plant material in 2021 from seeds? I cannot see this information in the text.

The information is at lines 122-123  “with 3-year-old saplings of Ailanthus altissima (Mill.) Swingle obtained from a nursery.”

 

How was the SPH pots irrigated?

The irrigation tubes were inserted in a small hole made in the mulch film, which was then sealed to avoid light penetration. Irrigation volume was one third that of the SH and SL treatments. We added this info in the methods section (L189-190).

 

Line 177: “…four treatments…”

Done

 

5. Results: You are presenting data only on the sprout number and biomass. More tables and figures are partly duplicate and could be combined. What about to publish your work as Short communication?

As the structure of the manuscript follows that of research articles and the introduction and discussion sections are more detailed than in a short communication, we would prefer to publish it as a research article.

 

There is no statistical analysis provided in Figures.

In the revised version we included more details for statistical significance. In figure 2, we added a few sentences in the text reporting the results of statistical analysis (lines 290-291 and 293-296), as the addition of letters in a line graph would be confusing. For figure 3 we marked with an asterisk the mean which was significantly different from all the others. In figure 4 we used different symbols or fonts to highlight statistical differences among treatments for each cut. Figure legends were improved to clarify the meaning of symbols.

 

I would imagine your functional model a little different (box and arrow based scheme).

Thank you for your suggestion. However, we feel that our figures better represent the increase of sprout number with the proceeding of the growth season and its correspondence with crown development.

Reviewer 2 Report

Comments and Suggestions for Authors

The work is of high practical significance. The methodology is described in detail, sometimes even too detailed (about 1 m above sea level).

Author Response

The work is of high practical significance. The methodology is described in detail, sometimes even too detailed (about 1 m above sea level).

Authors are grateful for having appreciated our manuscript. The details you mentioned as redundant were removed (L151).

Reviewer 3 Report

Comments and Suggestions for Authors

The manuscript submitted for evaluation is in line with the scope of the journal and the topic is of interest to a wide range of scientists and practitioners, especially those working in the field of invasive species control and eradication. Despite the strengths of the manuscript, I would like to draw the authors' attention to the shortcomings and points for discussion.

1. When giving the name of a taxon, according to the rules of plant nomenclature, the year is only cited (unlike in zoological nomenclature) when accompanied by a full bibliographic reference. As a result, '1916' in line 30 is redundant.

2. At the end of the introduction, I strongly recommend that the aim and the questions to be answered are clearly formulated and that the results and the discussion are presented in the sequence of the formulated questions.  

3. I doubt whether winter in the Mediterranean can be called 'cold' (line 127). It is better to specify a range of temperatures instead. In temperature regions, a 'cold winter' is when the average temperature is below -5°C. 

4. In Table 1 and throughout the text, I suggest that the dates are written according to the English standard (e.g. 1 March 2022). It is also quite confusing to understand exactly what the authors meant: '(25th and 21st July, respectively in 2022 and 2023)' (Line 191 and further). Is this to be understood as 25 July 2022 and 21 July 2023, or 5 July 2022, 21 July 2022, 5 July 2023 and 21 July 2023? This should be corrected so that there is no room for interpretation.

5. I suggest standardising the style of presentation. For example, Table 2 reads '25th July 2022 (Cut I)', while Table 3 already contains the same style of information in another way: 'Cut II (3rd October 2022)'. Uniformity and systematicity would only add to the quality of the article and would not make readers confused. 

6. I recommend that the discussion should explore whether environmental conditions other than those in the Mediterranean region might affect the success of resprouting? For example, higher rainfall, lower air temperatures in winter and summer (in Central European conditions). Could the results of the experiments be applied to other experiments carried out under natural conditions in other regions? 

 

Comments on the Quality of English Language

Only minor editing is required. 

Author Response

1. When giving the name of a taxon, according to the rules of plant nomenclature, the year is only cited (unlike in zoological nomenclature) when accompanied by a full bibliographic reference. As a result, '1916' in line 30 is redundant.

Thank you for highlighting this point. ‘1916’ was deleted

 

2. At the end of the introduction, I strongly recommend that the aim and the questions to be answered are clearly formulated and that the results and the discussion are presented in the sequence of the formulated questions.

Thank you for the recommendation. We re-arranged and improved the last paragraph of the introduction section as “In the present study, we investigated the role of light on the resprouting vigor from the stumps and roots of cut saplings, by arranging a pot experiment in which either stumps or the entire pot surface were covered with a black mulch film. A model of the timing and patterns of sprout emergence from stem and roots in relation to the phenology of intact control plants was presented to give insight into the sink-source relations among plant parts which may be determinants and drivers of resprouting vigor. We hypothesized that combining mechanical (cutting) and physical (light exclusion) control operations could minimise ailanthus resprouting without the use of chemicals and could, therefore, be applied without risks for human health and natural biodiversity.

 

3. I doubt whether winter in the Mediterranean can be called 'cold' (line 127). It is better to specify a range of temperatures instead. In temperature regions, a 'cold winter' is when the average temperature is below -5°C. 

We revised the climate classification for the site and rewrote the sentence as: “The climate is typical Mediterranean with hot arid summer (Csa) [29] and the mean temperatures being above 5 °C in the coldest month and above 22 °C in the hottest month.”

 

4. In Table 1 and throughout the text, I suggest that the dates are written according to the English standard (e.g. 1 March 2022). It is also quite confusing to understand exactly what the authors meant: '(25th and 21st July, respectively in 2022 and 2023)' (Line 191 and further). Is this to be understood as 25 July 2022 and 21 July 2023, or 5 July 2022, 21 July 2022, 5 July 2023 and 21 July 2023? This should be corrected so that there is no room for interpretation.

Dates were rewritten according to the English standard in table 1 and throughout the text.

 

5. I suggest standardising the style of presentation. For example, Table 2 reads '25th July 2022 (Cut I)', while Table 3 already contains the same style of information in another way: 'Cut II (3rd October 2022)'. Uniformity and systematicity would only add to the quality of the article and would not make readers confused. 

Done

 

6. I recommend that the discussion should explore whether environmental conditions other than those in the Mediterranean region might affect the success of resprouting? For example, higher rainfall, lower air temperatures in winter and summer (in Central European conditions). Could the results of the experiments be applied to other experiments carried out under natural conditions in other regions?

Thank you for this advice. We hope having fulfilled your request by adding the following comment to the discussion: “Though ailanthus displays a broad latitudinal range, at present it colonizes a wide range of habitats in the temperate regions of north America, while in Europe its occurrence is progressively confined to urban areas with the increase of latitude [1,4]. This difference, imputed to higher winter survival of sprouts because of warmer summers in the American region [4], may disappear in the close future due to climate change and it is to expect that in northern Europe ailanthus will show sprouting patterns like in the Mediterranean region in the next decades. In any case, we can presume that the length of the sprouting period and the rate of sprout growth will be related with the length of the vegetative season and the rate of biomass accumulation of intact plants in all colonized environments. Thus, by relating the timing of sprout development with the phenology of intact plants, our model may overcome the variability due to pedoclimatic conditions and can, therefore, be also applied in other regions.”