the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 28 Mar 2025
Do morphological hillslope features affect soil properties and processes promoting chestnut ink disease? The study case of the Northern Apennine mountains
Abstract. Ink disease caused by the soil-borne Phytophthora cambivora and Phytophthora cinnamomi is threatening sweet chestnut (Castanea sativa) groves in Europe. This study aims to explore whether soil morphology and its related properties influence the development of chestnut ink disease considering the whole soil depth. In C. sativa stand in Northern Italy, along a small altitudinal transect, soil profiles were dug close to ink diseased plants (INK1 at 978 m a.s.l.) and healthy plants (INK2 988 m a.s.l. and INK3 at 998 m a.s.l.) and each soil horizon evaluated for its properties. Further, INK1, INK2 and INK3 had a slope of 3, 9 and 30 %, respectively. The results showed that the lower slope position of INK1 combined with the lower slope gradient than INK2 and INK3 might have promoted the transport of clay particles and water from the latters to the former. Such process allowed the accumulation of clay within the whole INK1 soil profile increasing the saturated hydraulic conductivity and the wilting point. Such soil features might promote the water accumulation within the deeper soil horizons of INK1 which would explain the presence of Phytophthora spp. DNA. The presence of the root pathogen in INK1 might have affected the microbial functionality as observed by the higher abundance of the contact and medium-distance exploration ectomycorrhizal fungal community than the long-distance types. Finally, such study highlighted the pivotal role of soil processes (i.e., clay and water transport) to shape the soil microbial community and soil-borne pathogens because of the changes of edaphic properties.
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Status: closed
-
RC1: 'Comment on egusphere-2025-911', Anonymous Referee #1, 26 Jun 2025
- AC2: 'Reply on RC1', Mauro De Feudis, 06 Aug 2025
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RC2: 'Comment on egusphere-2025-911', James Kotcon, 16 Jul 2025
General Comments
A significant weakness in this study is that it appears to have very limited replication of treatment plots. It appears that a single soil profile was sampled at each of the three locations. If there were independent soil profiles sampled at each location, this would need to be better explained in the text. But if only a single tree was sampled, sampling from the various horizons would appear to be “pseudo-replication” rather than independent samples. Given that a “tree” would be the appropriate sample unit to assess plant disease, some indication of disease severity (e.g., % of roots infected or trunk canker size) at each site would be helpful. In addition, true replication would help resolve the soil site-by-horizon interaction that contributes to high within-site variability.
Overall, the Conclusions section seems to go much farther than the limited replication would allow. If the authors can document adequate replication, this paper could be acceptable. But a single soil profile per site is not adequate.
Specific Comments
Line 21. Why would clay “increase” hydraulic conductivity? While clay may increase water holding capacity, internal drainage tends to be reduced. I would have thought that conductivity is decreased. Water runs fastest through the biggest holes!
Alternatively, Table B3 indicates higher soil organic carbon at the INK1 site, compared to INK2 and INK3, was soil porosity or aggregate structure assessed?
Line 100. Please indicate the time of year that sampling took place. This is likely to affect disease severity, leaf mineral content, and various other parameters.
Line 112-114. It is unclear why soil sampling in other areas would prevent understanding of the relationship. At a minimum, replication of several trees within an orchard is needed to clarify which changes in microbial communities are causally related to soil factors versus those that are spurious and site specific.
Lines 123-125. Contrary to this statement, the data in Table appear to show no significant differences among sites in K and Ca, but higher levels of B (as well as P) in leaves at INK1 than in leaves from trees at healthy sites. The higher Mn levels in leaves at INK1 is not surprising given the lower soil pH shown in Appendix A, but acidic pH usually makes P less available, so the differences in leaf P warrant some explanation. Likewise, boron tends to be less available, when pH exceeds 6.5, so those results also need some explanation.
Lines 138-140. Was the same substrate used to assay both alpha and beta glucosidase? Should one of those substrates be the alpha-D-glucoside?
Lines 177-179. Hydraulic properties of the soil are key parameters influencing Phytophthora infection. Given that a major purpose of the paper is to assess the role of soil characters on Phytophthora infection, is there a reason those properties were not measured directly, rather than being inferred from the internet? Cropping history is likely to have a large effect on hydraulic properties, with cultivated soils having very different properties compared to a mature forest stand.
Line 180. Bulk density was used as an input variable, but the data do not appear to be presented here. Coupled with soil organic carbon, these data could help explain the disparity of sites with higher clay content having higher hydraulic conductivity. Can these bulk density data be added to the paper?
Lines 270-272. Figure C-2 illustrates diverse ground cover at these sites, and clarifying the species present is likely to be important in understanding the differences in plant pathogenic fungal communities. Tree roots typically represent a much smaller proportion of the rooting density than roots of herbaceous plants. Grasses in particular often have ten times the root length per unit of soil compared to perennial dicots. Ground cover plants may also disproportionately influence the mycorrhizal fungal community.
Lines 311-313. The conclusion that diseased “plants are altering the quality of organic matter reaching the soil” seems to not be well supported by these data. Are the diseased plants primarily affected by crown rot, or are fine feeder roots also infected? Given that soils at INK1 have higher total N than at INK2 or INK3, the higher OC and WEOC:WEN ratio seem to be just as likely due to higher overall plant productivity associated with a site with higher available water. Lines 316-317 hint at that, but need to be more explicit. Lines 348-349 share the same concern as above, and may not be warranted given the very limited replication of this study.
Lines 361-362. This appears to be anthropomorphizing fungal intent. Increases in ectomycorrhizal fungi are unlikely to be a “response” to the disease and does not necessarily result if they offer protection against the disease.
Lines 377-378. The limited replication severely undercuts the power of this study to draw conclusions about the relationship of soil properties to ink disease.
Line 378. Word Choice? The word “inoculation” means something entirely different than what is implied in its use here. How about “presence”?
Line 379. No “population dynamics” can be inferred from a single sample time.
Line 382. The “abundance of labile carbon” was not demonstrated to be a response to disease, and the higher soil N, coupled with high WEN, does not suggest limitations in nitrogen availability.
Technical Corrections
Line 13. Italicize Latin names (Phytophthora, Castanea, etc.)
Line 15. Insert “a” in front of “C. sativa stand…”
Line 66. Awkward sentence structure. Should “factor” be changed to “factors”? Or omit “considered soil forming factor”?
Lines 112-114. Awkard sentence structure. The meaning is unclear.
Line 660. Insert spaces in “hexamine cobalt(III) chloride”.
Line 675. Insert “after” after the word “days”.
Table B3. The column headings do not match the acronyms listed in the Table caption. Several column headings are not defined. For example, the text at line 136 defines
BR (Basal Respiration), but SBR is not defined here or elsewhere. As such, it is hard to interpret what the table actually reports.Citation: https://doi.org/10.5194/egusphere-2025-911-RC2 - AC1: 'Reply on RC2', Mauro De Feudis, 06 Aug 2025
Status: closed
-
RC1: 'Comment on egusphere-2025-911', Anonymous Referee #1, 26 Jun 2025
Trenti et al. investigated soil physicochemical properties and the microbial community along a slope gradient related to chestnut ink disease. This is an interesting study, and the results help to understand the factors relating to chestnut ink disease. However, the study is rather descriptive, and more analysis should be added to explore the underlying mechanisms.
- The introduction should clearly show the knowledge gaps. Why is slope a key factor affecting chestnut ink disease?
- How does slope affect soil biochemical properties and microbial communities related to chestnut ink disease?
- A comparison of pathogen (relative) abundance should be conducted between healthy and diseased trees, and the soil factors affecting pathogen abundance should also be explored.
- More analysis should be added to explore causal relations and the mechanisms leading to chestnut ink disease, e.g., structural equation modeling.
- The overall writing should be revised to be more concise, logical, and readable.
Citation: https://doi.org/10.5194/egusphere-2025-911-RC1 - AC2: 'Reply on RC1', Mauro De Feudis, 06 Aug 2025
-
RC2: 'Comment on egusphere-2025-911', James Kotcon, 16 Jul 2025
General Comments
A significant weakness in this study is that it appears to have very limited replication of treatment plots. It appears that a single soil profile was sampled at each of the three locations. If there were independent soil profiles sampled at each location, this would need to be better explained in the text. But if only a single tree was sampled, sampling from the various horizons would appear to be “pseudo-replication” rather than independent samples. Given that a “tree” would be the appropriate sample unit to assess plant disease, some indication of disease severity (e.g., % of roots infected or trunk canker size) at each site would be helpful. In addition, true replication would help resolve the soil site-by-horizon interaction that contributes to high within-site variability.
Overall, the Conclusions section seems to go much farther than the limited replication would allow. If the authors can document adequate replication, this paper could be acceptable. But a single soil profile per site is not adequate.
Specific Comments
Line 21. Why would clay “increase” hydraulic conductivity? While clay may increase water holding capacity, internal drainage tends to be reduced. I would have thought that conductivity is decreased. Water runs fastest through the biggest holes!
Alternatively, Table B3 indicates higher soil organic carbon at the INK1 site, compared to INK2 and INK3, was soil porosity or aggregate structure assessed?
Line 100. Please indicate the time of year that sampling took place. This is likely to affect disease severity, leaf mineral content, and various other parameters.
Line 112-114. It is unclear why soil sampling in other areas would prevent understanding of the relationship. At a minimum, replication of several trees within an orchard is needed to clarify which changes in microbial communities are causally related to soil factors versus those that are spurious and site specific.
Lines 123-125. Contrary to this statement, the data in Table appear to show no significant differences among sites in K and Ca, but higher levels of B (as well as P) in leaves at INK1 than in leaves from trees at healthy sites. The higher Mn levels in leaves at INK1 is not surprising given the lower soil pH shown in Appendix A, but acidic pH usually makes P less available, so the differences in leaf P warrant some explanation. Likewise, boron tends to be less available, when pH exceeds 6.5, so those results also need some explanation.
Lines 138-140. Was the same substrate used to assay both alpha and beta glucosidase? Should one of those substrates be the alpha-D-glucoside?
Lines 177-179. Hydraulic properties of the soil are key parameters influencing Phytophthora infection. Given that a major purpose of the paper is to assess the role of soil characters on Phytophthora infection, is there a reason those properties were not measured directly, rather than being inferred from the internet? Cropping history is likely to have a large effect on hydraulic properties, with cultivated soils having very different properties compared to a mature forest stand.
Line 180. Bulk density was used as an input variable, but the data do not appear to be presented here. Coupled with soil organic carbon, these data could help explain the disparity of sites with higher clay content having higher hydraulic conductivity. Can these bulk density data be added to the paper?
Lines 270-272. Figure C-2 illustrates diverse ground cover at these sites, and clarifying the species present is likely to be important in understanding the differences in plant pathogenic fungal communities. Tree roots typically represent a much smaller proportion of the rooting density than roots of herbaceous plants. Grasses in particular often have ten times the root length per unit of soil compared to perennial dicots. Ground cover plants may also disproportionately influence the mycorrhizal fungal community.
Lines 311-313. The conclusion that diseased “plants are altering the quality of organic matter reaching the soil” seems to not be well supported by these data. Are the diseased plants primarily affected by crown rot, or are fine feeder roots also infected? Given that soils at INK1 have higher total N than at INK2 or INK3, the higher OC and WEOC:WEN ratio seem to be just as likely due to higher overall plant productivity associated with a site with higher available water. Lines 316-317 hint at that, but need to be more explicit. Lines 348-349 share the same concern as above, and may not be warranted given the very limited replication of this study.
Lines 361-362. This appears to be anthropomorphizing fungal intent. Increases in ectomycorrhizal fungi are unlikely to be a “response” to the disease and does not necessarily result if they offer protection against the disease.
Lines 377-378. The limited replication severely undercuts the power of this study to draw conclusions about the relationship of soil properties to ink disease.
Line 378. Word Choice? The word “inoculation” means something entirely different than what is implied in its use here. How about “presence”?
Line 379. No “population dynamics” can be inferred from a single sample time.
Line 382. The “abundance of labile carbon” was not demonstrated to be a response to disease, and the higher soil N, coupled with high WEN, does not suggest limitations in nitrogen availability.
Technical Corrections
Line 13. Italicize Latin names (Phytophthora, Castanea, etc.)
Line 15. Insert “a” in front of “C. sativa stand…”
Line 66. Awkward sentence structure. Should “factor” be changed to “factors”? Or omit “considered soil forming factor”?
Lines 112-114. Awkard sentence structure. The meaning is unclear.
Line 660. Insert spaces in “hexamine cobalt(III) chloride”.
Line 675. Insert “after” after the word “days”.
Table B3. The column headings do not match the acronyms listed in the Table caption. Several column headings are not defined. For example, the text at line 136 defines
BR (Basal Respiration), but SBR is not defined here or elsewhere. As such, it is hard to interpret what the table actually reports.Citation: https://doi.org/10.5194/egusphere-2025-911-RC2 - AC1: 'Reply on RC2', Mauro De Feudis, 06 Aug 2025
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Trenti et al. investigated soil physicochemical properties and the microbial community along a slope gradient related to chestnut ink disease. This is an interesting study, and the results help to understand the factors relating to chestnut ink disease. However, the study is rather descriptive, and more analysis should be added to explore the underlying mechanisms.