Effects of Elemental Sulfur on Soil pH and Growth of Saskatoon Berry (Amelanchier alnifolia) and Beaked Hazelnut (Corylus cornuta) Seedlings
Round 1
Reviewer 1 Report
The authors present a study in which seedlings of two plant species (Saskatoon and beaked hazlenut) were grown in soils of two intial pH values (5.7 and 8.5) under three different sulfur treatments (0, 5 and 25 g Kg-1). The response of plant nutrient uptake, chlorophyll properties and photosynthesis/transpiration rates was monitored. Elemental sulfur additions lowered soil pH to an increasing degree with application rate. Despite the pH adjustment, measured physiological parameters generally decreased for both species at pH 5.7, with mixed responses observed for nutrient uptake. At pH 8.5, photosynthesis and transpiration rates were reduced with S addition in Saskatoon, although beaked hazlenut saw an increase in NPP at the highest S application rate. Nutrient uptake results at different S rates were mixed for each species, element and pH value. The authors conclude that elemental sulfur application rate must be carefully considered for remediation of open pit oil sands mining sites, as it might impact the health/growth of these two important boreal species. Overall, the study itself is rather simple and seems to have been conducted well with appropriate analyses and statistics. The results could very likely have some tangible implications for remediating the widespread oil-sands extraction sites in Western Canada. There are a few points that would benefit the reader to clarify a bit. I'd recommend minor revision for this manuscript.
General comments:
There are several references in the text to nutrient availability at different pH values, which is an important topic with respect to the questions being addressed here. Discussion linking these behaviors with mechanisms in the soil which are at the root of availability differences (such as precipitation, sorption or complexation) is scarce here.
Some experimental details are either unclear or not present. Primarily, there is little to no information given on the soil used in the study. The reader is provided a geographic reference and a pH value, but other important soil properties (e.g., taxonomy, texture, C/N content, CEC) are notably absent. Given the fact that this is a soil science journal and the soil itself plays such a critical role in plant health, this information should be included to help understand the broader applicability of these results.
What is the significance of the chl-a/chl-b ratio used in this study and what does it tell the reader about plant health?
How did the authors decide on using a two month growth window for this study?
How were the authors sure the oxidation of S was complete and, thus, the influence on pH was stabilized? In a field application, the S would be present longer and rates may have a larger effect on pH.
Line comments:
Figure 2d) The Beaked Hazlenut plot for total chlorophyll concentrations is missing the letters denoting significant differences.
Lines 261-262: Ca is present in most soils, what is the purpose of mentioning it is present in some reclamation soils here?
Lines 317-318: The biomass dilution effect is mentioned here without any description or explanation. The readership may benefit from some explanation, briefly, of what this is.
Lines 318-320: Blueberries tend to thrive in acidic conditions, so this may not be the best contrasting relationship to highlight.
Author Response
Comment from Reviewer 1:
The authors present a study in which seedlings of two plant species (Saskatoon and beaked hazlenut) were grown in soils of two intial pH values (5.7 and 8.5) under three different sulfur treatments (0, 5 and 25 g Kg-1). The response of plant nutrient uptake, chlorophyll properties and photosynthesis/transpiration rates was monitored. Elemental sulfur additions lowered soil pH to an increasing degree with application rate. Despite the pH adjustment, measured physiological parameters generally decreased for both species at pH 5.7, with mixed responses observed for nutrient uptake. At pH 8.5, photosynthesis and transpiration rates were reduced with S addition in Saskatoon, although beaked hazlenut saw an increase in NPP at the highest S application rate. Nutrient uptake results at different S rates were mixed for each species, element and pH value. The authors conclude that elemental sulfur application rate must be carefully considered for remediation of open pit oil sands mining sites, as it might impact the health/growth of these two important boreal species. Overall, the study itself is rather simple and seems to have been conducted well with appropriate analyses and statistics. The results could very likely have some tangible implications for remediating the widespread oil-sands extraction sites in Western Canada. There are a few points that would benefit the reader to clarify a bit. I'd recommend minor revision for this manuscript.
General comments:
There are several references in the text to nutrient availability at different pH values, which is an important topic with respect to the questions being addressed here. Discussion linking these behaviors with mechanisms in the soil which are at the root of availability differences (such as precipitation, sorption or complexation) is scarce here.
Some experimental details are either unclear or not present. Primarily, there is little to no information given on the soil used in the study. The reader is provided a geographic reference and a pH value, but other important soil properties (e.g., taxonomy, texture, C/N content, CEC) are notably absent. Given the fact that this is a soil science journal and the soil itself plays such a critical role in plant health, this information should be included to help understand the broader applicability of these results.
Response:
We have added more information on the soil properties in the text. Please see the lines 102-105.
What is the significance of the chl-a/chl-b ratio used in this study and what does it tell the reader about plant health?
Response: We added two sentences stating the rationales of analyzing chl-a/chl-b ration. Please see the lines 304-310.
How did the authors decide on using a two month growth window for this study?
Response: We added a statement explaining the reasons why the treatment lasted for two months. Please see the lines 279-281.
How were the authors sure the oxidation of S was complete and, thus, the influence on pH was stabilized? In a field application, the S would be present longer and rates may have a larger effect on pH.
Response: On lines 365-366, we added a statement that the chemistry dynamics of sulfur in the soil and the effect on soil pH should be better characterized and validated by field studies.
Line comments:
Figure 2d) The Beaked Hazlenut plot for total chlorophyll concentrations is missing the letters denoting significant differences.
Response: Thanks for noticing this. The figure has been corrected.
Lines 261-262: Ca is present in most soils, what is the purpose of mentioning it is present in some reclamation soils here?
Response: This sentence has been revised.
Lines 317-318: The biomass dilution effect is mentioned here without any description or explanation. The readership may benefit from some explanation, briefly, of what this is.
Response: This concept has been briefly explained.
Lines 318-320: Blueberries tend to thrive in acidic conditions, so this may not be the best contrasting relationship to highlight.
Response: We agree with this and we have removed this sentence and the associated reference.
Reviewer 2 Report
The article reads well however, the following changes need to be made before the publication:
- Line 44: define traditional areas
- Line 54-55: mentioned that high pH reduces the availability of Ca. explain
- Line 60:change water potential to water uptake
- line 71-72: replace problematic with crucial
- line 77:replace 'in the present study to for this study
- line 78-82: too long statement. Re-write (RW) the statement
- line 89-91: RW the statement
- line 116-119: RW the statement
- line 140: replace taken to selected
- line 148-151: RW statement
- line 168-169: how could pH 8.5 decline with calcium hydroxide? explain
- none of the tables have units. include proper units for each element listed
- line 249: remove "in the present study". no need
- line 274:remove 'woild'
- line 295-297: place the reference site in line 295 after 'other studies'
- line 308: it sounds like the statement in line 308 negates the discussions presented in line 304-307
- line 328: remove space after 'leaf'
- line 330-331: sounds contradictory
- line 353: start with a new paragraph with the heading: 'In conclusion'
- page 15-16: indent reference
Author Response
Comment from Reviewer 2:
The article reads well however, the following changes need to be made before the publication:
1. Line 44: define traditional areas
Response: This sentence has been revised to express the meaning of traditional areas more clearly.
2. Line 54-55: mentioned that high pH reduces the availability of Ca. explain
Response: We checked the literature source and found the deficiency of Mg and Ca in plants grown in high pH soils are uncommon, thus we removed these two elements.
3. Line 60:change water potential to water uptake
Response: This sentence has been revised.
4. line 71-72: replace problematic with crucial
Response: replaced.
5. line 77:replace 'in the present study to for this study
Response: changed.
6. line 78-82: too long statement. Re-write (RW) the statement
Response: We consulted with several colleagues, and they all think this statement is not improper. So, we think it should be OK to keep it like this.
7. line 89-91: RW the statement
Response: See above.
8. line 116-119: RW the statement
Response: See above.
9. line 140: replace taken to selected
Response: changed.
10. line 148-151: RW statement
Response: See response to comment 6.
11. line 168-169: how could pH 8.5 decline with calcium hydroxide? Explain
Response: We rephrased this sentence. Hopefully the logic is clearer now.
12. none of the tables have units. include proper units for each element listed
Response: We apologize for the confusion. Tables 1 and 2 are ANOVA tables showing p-values. We have added this information to both tables.
13. line 249: remove "in the present study". no need
Response: changed.
14. line 274:remove 'woild'
Response: removed.
15. line 295-297: place the reference site in line 295 after 'other studies'
Response: revised.
16. line 308: it sounds like the statement in line 308 negates the discussions presented in line 304-307
Response: We rephrased the expressions here and hoping the logic is clearer now.
17. line 328: remove space after 'leaf'
Response: removed.
18. line 330-331: sounds contradictory
Response: We have added “soil H+” concentrations” to clarify this statement.
19. line 353: start with a new paragraph with the heading: 'In conclusion'
Response: It has been formatted as a new paragraph in our version of the paper.
20. page 15-16: indent reference
Response: indented.
