Thirst or Malnutrition: The Impacts of Invasive Insect Agrilus mali on the Physiological Status of Wild Apple Trees
, Abid Ali 5,6, Xin Zhang 1, Xiaoxian Liu 1,2, Yuanming Zhang 1, Xiaobing Zhou 1 and Zhaozhi Lu 7,*Round 1
Reviewer 1 Report
Zhang et al 2020. There were some interesting aspects to this paper but it needs work, there are many simple English mistakes, please consider hiring a native speaker to copy edit manuscripts prior to submission. My job is to evaluate scientific value not correct English. I pointed out many examples of where the narrative needs editing to be widely understood. The science itself I thought was relatively solid and I found the topic very interesting but it was hard to follow. The introduction was brief and it did not introduce or justify the carbon ratio analysis very well. That turned out to be one of the more interesting aspects of the paper because the nutrient analysis did not amount to much. Some of the justification for the carbon ratio came in the results section, clearly not the place for it. The map figure was good but can be improved with a scale at a minimum, I had other suggestions for that in the notes below. I had a hard time following the discussion, including the second sentence. The bibliography has problems, none of the scientific names of organisms are in italics and there are other typos. I did not check reference numbers against the bibliography. I recommend major revision to address these issues. Below are some line numbered suggested changes that correspond with the marked-up manuscript attached.
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L23 from the Tertiary
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L45 is mainly distributed
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L47 a
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L51 of apple trees
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L51 in the 1990s or during the 1990s
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L52 damage was
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L52 of
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L57 side
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L58 the
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L58 is distributed accross
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L61 where in contrast with cultivated
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L64 to the following
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L71 associated
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L75 and the forest
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L76 reword: the ability of trees to utilize water is compromised
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L80 Reword: e.g. Recently, changes in volatile composition, soluble sugars and soluble proteins of trees after the infestation of A. mali were found to influence the development of pest insect or plant resistance to pests 83 [21, 22].
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were
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L83 how attack by A. mali
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L84 remain largely unexplained
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at large
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L90 among trees by damage rankings ?
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L91 annual? growing season? precipitation
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L92 s
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L96 A or the field
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L106 Figure 1 - Need a distance scale, good to include an overview map showing regional geography for international readers
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L115 three circular plots
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L129 report exact number of samples
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L135 seven random? leaves
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L136 were samples taken at the time of the survey for damage? This sentence very unclear, just give exact sample numbers not >
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L145 the leaf sample data
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L148 the carbon isotope data
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L149 as the dependent
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L154 Not Results:Stable carbon isotope ratio δ13C is primarily determined by the ratio of intercellular to ambient 155 CO2 concentrations (Ci/Ca), and the range of its variation is coordinated and constrained by stomatal 156 conductance and photosynthetic rate [27]. In general, stable carbon isotope discrimination in leaves 157 is reduced when plants are under abiotic stresses that may cause the decrease in stomatal 158 conductance. For instance, water deficit due to vascular tissue damage caused by trunk borers may 159 lead to the decrease in stomatal conductance, which lowers intercellular CO2 concentration and 160 renders plants to incorporate more 13C into photosynthates.
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s
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on
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L198 This damage
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L200 in the xylem
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L200 leading to more water stress, compounding water stress
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L209 classes of 209 damages
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es
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L212 cultivated apple trees showing symptoms of "rapid apple decline" in North America
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L214 herbivores
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different
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L220 an
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foliar chemicals
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infestation
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s
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the
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L266 italics: Malus sieversii
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Agrilus mali.
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Agrilus mali
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Malus sieversii
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Agrilus mali
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Agrilus mali
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Agrilus mali
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Agrilus mali
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Fraxinus pennsylvanica)
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Agrilus planipennis) i
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Adelges tsugae) infe
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Tsuga canadensis
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l Entomol2013, 38, 627–630.
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Eogystia hippophaecolus
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Dendroctonus ponderos
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nt Ecol Evol2016, 4,
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Phoracantha semipunctata F.
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rilus auroguttatus, in
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rilus planipennis) and ash (
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Agrilus ma
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Malus Sievers
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rilus mali
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer,
Thank you very much for your time and your invaluable revision comments. We have carefully studied all your comments and tried our best to revise the manuscript accordingly. We listed our responses to each of your comments as below. Please refer to the line number in review – simple makeup mode. For the purpose of easy tracking in the main text, we highlighted our responses to Reviewer 1 in green, and our responses to Reviewer 2 in yellow. To further improve the quality of manuscript, we presented our additional opinions, in blue font.
Your comments have substantially helped us with improving the manuscript. Please kindly review the revised version. We look forwards to hearing your feedbacks.
Sincerely,
Ping Zhang
On behalf of the authors
Responses to Reviewer 1’s comments
Point 1: The introduction was brief and it did not introduce or justify the carbon ratio analysis very well
Response 1: In Introduction, we have added some information about plant water relations and case studies of pest infestation, to justify the stable isotope analysis. The changes were made in Line 78 – 89: “Generally, tree water use declines after pest infestation. Lower leaf water potential and cell turgor potential have been reported subsequent to the damage by Agrilus species [19, 20], indicating that trees were experiencing water deficit. Water deficit due to vascular tissue damage caused by trunk borers may lead to the decrease in stomatal conductance, which lowers intercellular CO2 concentration and renders plants to incorporate more 13C into photosynthesis. This subtle change can be captured in stable carbon isotope ratio δ13C, an indicator for long-term water use efficiency. The δ13C is primarily determined by the ratio of intercellular to ambient CO2 concentrations (Ci/Ca), and the range of its variation is coordinated and constrained by stomatal conductance and photosynthetic rate [21]. In the oak trees infested by Agrilus auroguttatus and the ash trees infested by emerald ash borer (Agrilus planipennis), the change in δ13C was in synchronization with other plant water relations parameters, and was proven to be a sensitive indicator for plant water stress [19, 20] .”
Point 2: Some of the justification for the carbon ratio came in the results section, clearly not the place for it.
Response 2: We moved the justification for carbon ratio analysis from Results to Introduction.
Point 3: The map figure was good but can be improved with a scale at a minimum, I had other suggestions for that in the notes below.
Response 3: We edited the map to include the scale.
Point 4: I had a hard time following the discussion, including the second sentence.
Response 4: We made a few revisions to improve the flow of discussion and to make it more readable. Please review the changes highlighted in Discussion. We also added a subheading for each paragraph, read as “4.1 Tree dieback and borer-induced water stress”, “4.2 Confluent impacts of pest infestation and drought”, and, “4.3 Potential impacts of nutrient deficiency”.
Point 5: The bibliography has problems, none of the scientific names of organisms are in italics and there are other typos. I did not check reference numbers against the bibliography. I recommend major revision to address these issues.
Response 5: We have carefully checked each reference number and italicized the scientific names of organisms.
Point 6: Highlight, page 1 L23 from the Tertiary
Response 6: We made the following revision in Line 21-22.
“Malus sieversii (Ledeb.) M. Roem is a Tertiary relict tree species, and a rare and valuable resource for germplasm conservation.”
Point 7: Highlight, page 2 L45 is mainly distributed
Response 7: We made revision in Line 45-46, according to the suggestion.
Point 8: Highlight, page 2L47 a
Response 8: We replaced “one of” with “a” in Line 47.
Point 9: Highlight, page 2L51 of apple trees
Response 9: We changed it to the plural form.
Point 10: Highlight, page 2L51 in the 1990s or during the 1990s
Response 10: We made revision accordingly.
Point 11: Highlight, page 2L52 damage was
Response 11: We made revision accordingly, and changed “damage” to the singular form throughout the text.
Point 12: Strike Out, page 2L52 of
Response 12: We deleted it in Line 53.
Point 13: Strike Out, page 2L57 side
Response 13: We deleted it in Line 58 .
Point 14: Strike Out, page 2L58 the
Response 14: We deleted it.
Point 15: Highlight, page 2L58 is distributed across
Response 15: We made revision accordingly in Line 59.
Point 16: Highlight, page 2L61 where in contrast with cultivated
Response 16: We made revision accordingly in Line 62.
Point 17: Highlight, page 2L64 to the following
Response 17: We made revision accordingly in Line66.
Point 18: page 2, L71 associated
Response 18: We made revision accordingly in Line 72.
Point 19: page 2, L75 and the forest
Response 19: We made revision accordingly in Line 77.
Point 20: page 2L76 reword: the ability of trees to utilize water is compromised
Response 20: The sentence was revised as “tree water use declines after pest infestation”, and moved to Line 78.
Point 21: page 2L80 Reword: e.g. Recently, changes in volatile composition, soluble sugars and soluble proteins of trees after the infestation of A. mali were found to influence the development of pest insect or plant resistance to pests 83 [21, 22].
Response 21: It has been revised as “For example, it was recently found that changes in volatile composition, soluble sugars and soluble proteins of trees after the infestation of A. mali influenced the development of pest insect or plant resistance to pests”, in Line 91-93.
Point 22: page 2L83 how attack by A. mali
Response 22: It has been revised accordingly in Line 94.
Point 23: page 2L84 remain largely unexplained
Response 23: It has been revised accordingly in Line 95.
Point 24: Strike Out, page 2at large
Response 24: It has been deleted in Line 95.
Point 25: page 2L90 among trees by damage rankings ?
Response 25: Yes. We revised accordingly in Line 101.
Point 26: page 2 L91 annual? growing season? precipitation
Response 26: We clarified that it was growing season, in Line 102.
Point 27: page 3L106 Figure 1 - Need a distance scale, good to include an overview map showing regional geography for international readers.
Response 27: Figure 1 was revised accordingly.
Point 28: L115 three circular plots
Response 28: We revised it accordingly in Line 130.
Point 29: page 4L129 report exact number of samples
Response 29: We reported the exact number of samples (Table 1 )in Line 163-164. “There were 69 samples in total in 2016, including 14 samples in Class 1, 20 in Class 2, 20 in Class 3 and 15 in Class 4. There were 80 samples in total in 2017, including 20 samples in each damage ranking.”
Point 30: page 4L135 seven random? leaves
Response 30: Yes. In Line 153, we clarified that six to seven leaves were randomly selected and pooled as one sample for mineral nutrient analysis.
Point 31: page 4 L136 were samples taken at the time of the survey for damage? This sentence very unclear, just give exact sample numbers not
Response 31: Yes, we explained that samples were taken at the time of the survey for damage in Line 142. We reported exact numbers (Table 1) in Line 163-164, and explained that the inconsistent number of replicates was due to shortage of samples in some damage ranking in either year.
Point 32: page 5L145 the leaf sample data
Response 32: It was revised in Line 166-167.
Point 33: Highlight, page 5L148 the carbon isotope data
Response 33: It was revised in Line 166.
Point 34: Highlight, page 5L149 as the dependent
Response 34: It was revised in Line 169.
Point 35: trike Out, page 5L154 Not Results:Stable carbon isotope ratio δ13C is primarily determined by the ratio of intercellular to ambient 155 CO2 concentrations (Ci/Ca), and the range of its variation is coordinated and constrained by stomatal 156 conductance and photosynthetic rate [27]. In general, stable carbon isotope discrimination in leaves 157 is reduced when plants are under abiotic stresses that may cause the decrease in stomatal 158 conductance. For instance, water deficit due to vascular tissue damage caused by trunk borers may 159 lead to the decrease in stomatal conductance, which lowers intercellular CO2 concentration and 160 renders plants to incorporate more 13C into photosynthates.
Response 35: This paragraph has been moved to Introduction in Line 83-86.
Point 36: Highlight, page 7L198 This damage
Response 36: It was revised in Line 216.
Point 37:Highlight, page 7L200, an embolism
Response 37: It was revised in Line 217.
Point 38:Highlight, page 7L200 in the xylem
Response 38: It was revised in Line 217.
Point 39: Highlight, page 7L200 leading to more water stress, compounding water stress
Response 39: We revised it as “led to more compounded water stress” in Line 218.
Point 40:Highlight, page 7L212 cultivated apple trees showing symptoms of "rapid apple decline" in North America
Response 40: We revised accordingly in Line 230.
Point 41: Highlight, page 7 L214 herbivores
Response 41: We revised accordingly in Line 237.
Point 42: Strike Out, page 7different
Response 42: It was deleted.
Point 42: Highlight, page 7L220 an
Response 42: In Line 245, We revised it accordingly in Line 249-250.
Point 43: Highlight, page 7foliar chemicals
Response43: We rewrite the sentence as it was“While feeding on the xylem of twigs in hemlock, A. tsugae may cause an increase in foliar nutrient levels due to the feeding habits of its trigger foliar related intermittent stress events it accordingly”in Line 249-250.
Point 44: delete the infestation
Response 44: It was deleted from Line 251
Point 45: Highlight, page 7L225 from
Response 45: We double checked and kept the expression as it was. “It was possible that N, P, K , Ca2+and Mg2+ had been mobilized to relatively healthier tissues prior to defoliation”, is what we intended to express in Line 254.
Point 46: Strike Out, page 7s
Response 46: It was deleted from Line 257.
Point 47: Strike Out, page 7The
Response 47: It was deleted from Line 272 .
Author Response File: 
Author Response.doc
Reviewer 2 Report
Zhang and colleagues report the results of research exploring how infestation by the buprestid Agrilus mali affects leaf stomatal conductance and nutrient content in wild apple trees. They did a multi-site survey of trees in five different damage classes (ranging from lightly to severely damaged to dead) over two different years, collected leaves at random from trees in each of the damage classes, and then analyzed them. Damage was correlated with decreased water use efficiency (WUE) in a dry year but not in a wet year; in neither year was there a correlation between damage and foliar nutrient content.
This is a solid piece of work, although what it finds isn’t particularly surprising. Since Agrilus is a cambium feeder, and since cambium feeding disrupts the phloem and xylem, it makes sense that damaged branches would have decreased WUE. Because larvae are found much more often on branches than on the trunk (a fact mentioned in Bozorov et al 2019), there shouldn’t be a ‘systemic’ effect of this damage: in other words, undamaged branches on a damaged tree should closely resemble branches on a pest-free tree. Their methods section implies that leaves were removed at random from branches of trees within a given damage class. If so, then most of the leaves collected during a random sampling of lightly-damaged trees would be from undamaged branches, and vice versa. I suspect that this ‘sampling effect’ likely explains the wide variation around the means in the data… if they only sampled damaged branches from trees in the four classes (excluding five, which doesn’t have any leaves), I bet they wouldn’t find any difference between damage classes. The ‘systemic’ effect of Agrilus is thus likely a sum of the branch-level effects… something that’s generally true of branch feeders (but not trunk/root borers, whose effects are often apparent far from the actual damage).
Nutrient work: Since there’s no evidence that Agrilus is manipulating plant physiology (unlike sessile feeders such as Adelges tsugae), I also wasn’t surprised that leaf nutrient content didn’t change… but this work is useful for confirming what we think shouldn’t matter actually doesn’t :)
A logical point: The fact that the relationship between damage and WUE is significant in 2016 but not 2017 is consistent with the hypothesis that drought exacerbates the impact of Agrilus on WUE. Since the data isn’t experimental (i.e., you didn’t manipulate water availability to trees held under otherwise identical conditions and then measure the effect of pest damage), however, the authors need to be careful about stating that a cause-effect relationship exists between the two variables (even though it probably does).
I’ve made many line edits to the attached manuscript: errors are highlighted, and I’ve inserted comments where the text was unclear.
Comments for author File: Comments.pdf
Author Response
Dear Reviewer,
Thank you very much for your time and your invaluable revision comments. We have carefully studied all your comments and tried our best to revise the manuscript accordingly. We listed our responses to each of your comments as below. Please refer to the line number in review – simple makeup mode. For the purpose of easy tracking in the main text, we highlighted our responses to Reviewer 1 in green, and our responses to Reviewer 2 in yellow. To further improve the quality of manuscript, we presented our additional opinions, in blue font.
Your comments have substantially helped us with improving the manuscript. Please kindly review the revised version. We look forwards to hearing your feedbacks.
Sincerely,
Ping Zhang
On behalf of the authors
Responses to Reviewer 2’s comments
Point 1: This is a solid piece of work, although what it finds isn’t particularly surprising. Since Agrilus is a cambium feeder, and since cambium feeding disrupts the phloem and xylem, it makes sense that damaged branches would have decreased WUE. Because larvae are found much more often on branches than on the trunk (a fact mentioned in Bozorov et al 2019), there shouldn’t be a ‘systemic’ effect of this damage: in other words, undamaged branches on a damaged tree should closely resemble branches on a pest-free tree. Their methods section implies that leaves were removed at random from branches of trees within a given damage class. If so, then most of the leaves collected during a random sampling of lightly-damaged trees would be from undamaged branches, and vice versa. I suspect that this ‘sampling effect’ likely explains the wide variation around the means in the data… if they only sampled damaged branches from trees in the four classes (excluding five, which doesn’t have any leaves), I bet they wouldn’t find any difference between damage classes. The ‘systemic’ effect of Agrilus is thus likely a sum of the branch-level effects… something that’s generally true of branch feeders (but not trunk/root borers, whose effects are often apparent far from the actual damage).
Response 1: We truly appreciate the reviewer’s professional points of view with regards to the differential plant physiological responses to the damage caused by branch feeder and trunk borer, and the concern about possible sampling effect. We would like to elaborate our understanding about systematic versus localized effect, to justify our sampling method, as below.
- The duration of the damage: The forest in our study has been infested by this pest for almost 20 years. In the field, more than 95% of the trees were infested. It was hard to find a tree that was completely clear from damage after 20 years of its widespread in the forest ecosystem. To this point, any short-term, localized effect would have exerted cumulative impacts on the whole tree level and even on the ecosystem scale.
- Dynamics within a tree: Although a branch phloem feeder pest likely doesn’t cause damage in a systematic manner as a trunk borer can do, we would argue that the effect of Agrilus on the tree is beyond the sum of directly damaged branches. The transport and partitioning of water, nutrients, carbohydrates and phytohormones is highly dynamic amongst different components in the plant. For example, a decrease in leaf area due to the localized branch damage could reduce the total water and nutrient uptake as well as photosynthates assimilation by a tree. Nutrient mobilization between damaged and undamaged branches is also possible. In an unpublished study by our colleague Dr Zhang Qin, the sap flux, which presented the systematic hydraulic conductivity of a tree, declined in the trees damaged by Agrilus, compared to the healthy trees. However, within an infested tree, the hydraulic conductivity was not significantly different between damaged branches and undamaged branches. This indicates that randomly sampled branches of a tree can represent the average hydraulic status on the whole tree level. More controlled experiments in the future will certainly help to elucidate any differentiation between systematic and localized effects.
Our study aimed to elucidate why individual wild apple trees responded to Agrilus infestation differentially, and to explain the tree dieback mechanism from the physiological perspectives of water stress and nutrient deficiency. On each surveyed tree, we conducted random sampling from all the remaining branches that still had living leaves. By doing so, we minimized any possible sampling effect on stable isotope analysis and nutrient analysis, and were able to obtain reliable data to demonstrate any water deficit or nutrient deficiency on a whole tree level. We included additional discussion in Line 241-244.
Point 2: Nutrient work: Since there’s no evidence that Agrilus is manipulating plant physiology (unlike sessile feeders such as Adelges tsugae), I also wasn’t surprised that leaf nutrient content didn’t change… but this work is useful for confirming what we think shouldn’t matter actually doesn’t :)
Response 2: Agrilus larvae are phloem feeder and are not known to manipulate plant physiological performance in a short term. However, we speculate that the sink-source dynamics between leaves and branches, and between damaged and undamaged branches, are involved in the mobilization of nutrients. To address this in future studies, 32P and 15N labelled nutrients can be used to trace the element movement in controlled experiments. We proposed this in Line 259-261.
Point 3: The fact that the relationship between damage and WUE is significant in 2016 but not 2017 is consistent with the hypothesis that drought exacerbates the impact of Agrilus on WUE. Since the data isn’t experimental (i.e., you didn’t manipulate water availability to trees held under otherwise identical conditions and then measure the effect of pest damage), however, the authors need to be careful about stating that a cause-effect relationship exists between the two variables (even though it probably does).
Response 3: Yes we agree. We made revision on our statement in Line 222-227and Line 231-233.
Point 4: on page 1, L28, Explain what ?
Response 4: We made revision as “…explain the wild apple dieback…” in Line 27.
Point 5: on page 1, L29, the tree of M. sieversii
Response 5: we deleted “the tree of” in Line 28.
Point 6: on page 1, L40, chronic thirst of wild apples
Response 6: We changed it to “long-term water deficit”, in Line 37.
Point 7: on page 2, L56, no idea where this is
Response 7: we added “in the Yili River Valley in Xinjiang” in Line 54, and added an overview map in Figure 1.
Point 8: on page 2, L77, Water availability of forest ecosystems declines following pest invasion? Really?
Response 8: We made revision in Line 76-77. “Stresses aggravate each other and develop into a cascade that accelerates the heath deterioration of trees and the forest ecosystem [18].
Generally, tree water use declines after pest infestation.”
Point 9: on page 2, L84, confusing sentence - please reword
Response 9: This sentence has been rewritten as “for example, it was recently found that changes in volatile composition, soluble sugars and soluble proteins of trees after the infestation of A. mali influenced the development of pest insect or plant resistance to pests”, in Line 91-93.
Point 10: on page 3, L98, not what... should be whether
Response 10: We revised it in Line 104.
Point 11: on page 3, L107, salt-based substances?
Response 11: W changed it to carbonate salts in Line 113-114.
Point 12: on page 5, L123, There was at least three km between each plot.
Response 12: Based on your comments, the sentence “in the distance of at least 3 km from one another” has been corrected to “there was at least three kilometres between plots”, in Line 131.
Point 13: on page 5, L125, Please give the % of total surveyed trees that fell into each category. Did any trees change damage classes between 2016 and 2017?
Response 13: (1) The specific data have been shown in Table 1.(In 2016, the trees in Class 1, 2, 3 and 4 represented 32.04%, 26.33%, 22.85% and 18.78% of the surveyed wild apple population, respectively. In 2017, the percentage for Class 1- 4 was 36.47%, 25.84%, 23.91% and 13.76%, respectively) (2) In fact, the damage ranking of trees vary from year to year due to the self-repairing ability of the trees. However, according to our research on the relationship between the DBH and the damage ranking of the tree, we found that the change of damage ranking between is about 1~10% in short-term years. In this study, the annual interval is only one year. So, there were slight change of damage ranking. We believe that each damage ranking is maintain at same level.
Point 14: on page 5, L128, Were the branch you sampled on each tree ones that had evidence of damage?
Point 15: on page 5, L136, Again each class- is this from damaged branches?
Response 14and15: Each damage class was ranked by the whole tree health status.We randomly selected branches that were representative for the tree, for sampling. Sampling included the branches with different extent of damages. We clarified in Line 142.
Point 16: on page 5, L138, What does 'n' refer to here? What does 'n' mean?
Response 16: We added details to explain the number of replicates (Table 1) in Line 163-164, and Line 155-156. The inconsistent number of replicates was due to shortage of samples in some damage ranking in either year.
Point 17: on page 5, L167-173, none of the highlighted text is a result - remove it.
Response 17: According to Reviewer 1’s suggestion, we moved it to Introduction.
Point 18: on page 5, L173, You can't say that C increased with damage ranking in both years - only in 2016 was there a statistically significant correlation between the two variables
Response 18: We have corrected the statement in Line 174-176, as “the change of leaf δ13C with the damage rankings exhibited the difference between years. The values of leaf δ13C in the same ranking were slightly higher in 2016 than in 2017”.
Point 19: on page 8, L196, I don't understand this sentence‘Based on the theory that the seasonal decrease in stomatal conductance is coupled with higher 13C/12C ratio, i.e., a more positive or less negative δ13C‰, which stands for a time-integrated estimate of lower intrinsic WUE’
Response 19: We made revision in Line 198-200, as “the seasonal decrease in stomatal conductance is coupled with a higher 13C/12C ratio, i.e., a less negative δ13C‰ value. Unlike transient WUE data, this value stands for a long-term integrated estimate of lower intrinsic WUE over the season”.
Point 20: on page 9, L217, non-significant in 2017 - the two variables were not statistically correlated
Response 20: We made revision in Line 222-226.
Point 21: on page 9, L223, untrue - there's no evidence that water stress increased pest pressure
Response 21: We made revision in Line 221-226, as “it is worth noting that the change in δ13C showed similar trend among damage rankings in both years. There was significant difference among rankings in 2016, which had a drier late winter and growing season. In contrast, the values of δ13C were not significantly different among damage rankings in 2017, the year with higher precipitation in late winter and during the growing season. The values of δ13C in same damage ranking were significantly different between 2016 and 2017”.
Point 22: on page 9, L235, A. tsugae is not a foliar-feeding pest
Response 22: We changed it to phloem feeding on twigs, in Line 248.
Point 23: on page 9, L235-236, You'll need an example other than A. tsugae here - it's not a foliar feeder, and the increases in foliar nutrient levels are a result of the insect manipulating the plant (see Gómez et al. 2012. Oecologia 169(4): 1015-1024)
Response 23: We added another example in Line 246-248, as “for instance, Eogystia hippophaecolus could cause the decrease of some mineral element contents in the damaged root and trunk of the host Holcocerus hippophaecolus [15]”. However, we also think the study of A. tsugae is a good example. So, we re-clarified the change of foliar nutrient caused by the pest and added the reference (number 43), in Line 248-250.
Point 24: on page 9, L247, But WHY were they predisposed in the first place? What's different about them? That's a really interesting question, but one that your work doesn't address... so I wouldn't mention it here.
Point 25: on page 9, L252, How would watering wild apple trees prevent outbreaks?
Response 24 and 25: Trees in good water status are less susceptible to biotic stresses. We made revision to address the reviewer’s questions, in Line 271-276.
“This will pose a serious risk to the persistence of wild apple forest in Tienshan Mountain. When trees are under moderate water conditions, they become less susceptible to existing or emerging biotic stressors. Therefore, in conservation hotspots, aerial irrigation would be a necessary mitigation approach to alleviate water stress and protect the invaluable wild apple forests from further decline, which could help to prevent the further spreading of A. mali to other Malus forests and the adjacent production zones of domestic apples. ”
Author Response File: Author Response.doc
Round 2
Reviewer 1 Report
The authors did a good job with the revisions, and I feel the paper can now be accepted for publication.
