Regional Climate, Edaphic Conditions and Establishment Substrates Interact to Influence Initial Growth of Black Spruce and Jack Pine Planted in the Boreal Forest

Round 1

Reviewer 1 Report

This manuscript analysed the influence of regional climate, soil conditions on the establishment of black spruce and jack pine seedlings.

The subject is quite important for the northeastern part of America, as these two tree species are the most planted ones. The information revealed in this study has a potential impact on forest management, especially in the province of Quebec.

Several points need to be clarified:

The plantation analyzed grew several years from 2011 to 2016. Tree growth was measured after a three-year growth period for all the seedlings in the forest. This raises the question about the climatic conditions differences for seedling measured during different years. This point has to be addressed. The lack of informations with regard to seedling tree height at the time of planting, as well as ring-width measurements after 3 years, is a serious concern. What are the quantitative variations between seedling at the beginning of this study and at the end? Which parameters did you consider to make 4 groups? Extrapolated climatic data? The result could significantly change given the groups selected. Thus, you should present clearly the basic subdivision of the data. Another important concern is related to the apparent link between figures 2 and 3. Both figures are difficult to read and there is no mention of this link in the discussion (refer to your figures and table 1).

Many comments are written directly into the manuscript.

Comments for author File: Comments.pdf

Author Response

We thank you for the fast and thorough review of our manuscript. Please find attached the revised version entitled " Regional climate, edaphic conditions and establishment substrates interact to influence initial growth of black spruce and jack pine planted in the boreal forest". We thank the reviewers for their constructive comments. Based on their suggestions, we have significantly improved our manuscript, notably in the Introduction and Methods sections. You will find our additions and modifications in the main text, highlighted in yellow. Our point-by-point answers and comments are below, in blue.

 

We hope you will find that this modified version is up to the high standards of Forests, and are looking forward to your decision.

 

Mohammed Henneb and co-authors

 

Reviewer 1

English language and style

( ) Extensive editing of English language and style required 
( ) Moderate English changes required 
( ) English language and style are fine/minor spell check required 
(x) I don't feel qualified to judge about the English language and style 

 

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	( )	(x)	( )	( )
Is the research design appropriate?	( )	(x)	( )	( )
Are the methods adequately described?	( )	(x)	( )	( )
Are the results clearly presented?	( )	(x)	( )	( )
Are the conclusions supported by the results?	( )	(x)	( )	( )

 

General Comments

The plantation analyzed grew several years from 2011 to 2016. Tree growth was measured after a three-year growth period for all the seedlings in the forest. This raises the question about the climatic conditions differences for seedling measured during different years. This point has to be addressed.

Thank you for this comment. The climate data we used as explaining variables corresponded to the 3-year growth periods specific to each plantations included in our dataset. Hence, our analyses of seedling growth are sound. Moreover, the use of data covering the 2011-2016 period (with matched seedling-climate data within that period) provides a larger gradient of conditions and thus, increase the inference potential of our study. The use of matching climate-seedling growth data is explained in the methodology section as follows:

Line 86-87: “Twenty-one cutblocks were reforested with black spruce between 2010 and 2016; eight cutblocks were reforested with jack pine between 2011 and 2016 (Figure 1).”

Line 120-123: “The climatic data were collected from May to September (growing season) during the first three growing seasons for each cutblocks; i.e. climate data we used as explaining variables corresponded to the 3-year growth periods specific to each plantation included in our dataset.”

The lack of informations with regard to seedling tree height at the time of planting, as well as ring-width measurements after 3 years, is a serious concern. What are the quantitative variations between seedling at the beginning of this study and at the end?

We expressed black spruce and jack pine seedling growth using relative volume growth (RGRV), calculated from the final volumes (end of the 3rd growing season) and initial volumes (1st growing season) (see eq 2). Final and initial volumes were calculated using the final and initial heights and diameters of each seedling (see eq 1). The use of RGR takes into account the potential initial differences in size between the seedlings.

Line 125-131: “ We conducted all statistical analyses in R version 3.5.1 [29]. We used seedling height and ground collar diameter data to calculate a volume index (V), based upon the volume of a cone [30], which was computed as follows:

V = π × (D/2)2 x (H/3)

(1)

where V is volume in cm³, D is bole diameter at ground level (cm), and H is height (cm). We then calculated relative volume growth (RGRV), following [10], according to the following formula:

RGRV= [In (V3) -In (V0)] /[t3-t0]

(2)

where V3 and V0 represent tree volumes at time t3 (i.e., after three growing seasons) and t0 (at planting).”

Following the reviewer advice, we added a table (new table 1) to present seedling height (cm) and collar diameter (mm) at the end of their 3rd growing season in the different regions of our study area.

Line 156-163: “Our dataset comprised 4,492 seedlings distributed across the two species and over the four regions (Table 1). After three growing seasons, blacks spruce seedling ground collar diameter and height ranged from 9.6 to 18 mm and from 47 to 90 cm, respectively, with the larger sizes observed in the wetter regions. Jack pine seedlings, which were only found in the dry regions, respectively ranged from 10.2 to 15.2 mm in ground collar diameter and from 44 to 69 cm in height.

 

Table 1. Number of jack pine and black spruce seedlings in the four regions, with corresponding height and ground collar diameter at the end of their third growing season.

Species	Region	Number of seedlings	Ground collar diameter (mm)	Height (cm)
Black spruce	Wet-Warm	1120	18.0 (±6.3)	89.7 (±26.8)
	Wet-Cold	1289	12.9 (±5.2)	61.8 (±27.0)
	Dry-Warm	239	9.6 (±4.6)	51.4 (±18.2)
	Dry-Cold	348	9.6 (±6.6)	47.1 (±21.9)
Jack pine	Dry-Warm	1034	15.2 (±6.7)	69.3 (±25.1)
	Dry-Cold	462	10.2 (±2.5)	44.1 (±9.6)

Note: Data are presented as mean (±standard deviations)”

 

Which parameters did you consider to make 4 groups? Extrapolated climatic data? The result could significantly change given the groups selected. Thus, you should present clearly the basic subdivision of the data. 

We have indeed used extrapolated monthly data obtained from NASA’s Global Climate Data Platform, and then used the median of the temperature gradient (from south to north) and precipitation gradient (from east to west) as boundaries to delineate the four regions. We have made the following changes and additions to the text to explain our method more clearly:

Line 118-120: “At the regional level, extrapolated monthly data were extracted for temperature, total precipitation and relative humidity from NASA's Global Climate Data Platform (2-metre resolution) (https://power.larc.nasa.gov/data-access-viewer/).”

Line 142-149: “Last, we used medians of mean monthly temperature (13.5 °C) and total monthly precipitation (95.9 mm) as boundaries to delineate four groups: dry and cold region; wet and cold region; dry and warm region; and wet and warm region. We preferred median values of temperature and precipitation to mean values to delimit the four regions as they are relatively insensitive to outliers and detects break point to subdivide data into several groups [32–34]. This method has been applied successfully in ecology in previous studies [35,36]. Table 1 summarizes the number of black spruce and jack pine seedlings in each delineated region.”

Another important concern is related to the apparent link between figures 2 and 3. Both figures are difficult to read and there is no mention of this link in the discussion (refer to your figures and table).

Figure 2 presents PCA results for black spruce, which was found in the four climate regions, whereas figure 3 presents results for jack pine, only found in two of the climate region. The short paragraph added at the beginning of the result section (line 156-160) clearly explains jack pine was not found in all of the four quadrants:

 

Line 156-160: “Our dataset comprised 4,492 seedlings distributed across the two species and over the four regions (Table 1). After three growing seasons, blacks spruce seedling ground collar diameter and height ranged from 9.6 to 18 mm and from 47 to 90 cm, respectively, with the larger sizes observed in the wetter regions. Jack pine seedlings, which were only found in the dry regions, respectively ranged from 10.2 to 15.2 mm in ground collar diameter and from 44 to 69 cm in height.”

We have changed the order of the four PCAs presented in Figure 2 (a to d) and the two PCAs of Figure 3 (a and b), so that it follows the distribution order of the four regions of our study area shown in Figure 1. The order is as follows: Dry-Cold region, Cold-Wet region, Warm-Dry region and Warm-Wet region. The text of the manuscript has been readjusted to reflect this order.

Also, we have improved the appearance of figures 2 and 3 by increasing the label font (See figures 2 and 3). We have referred to Table 1 and Figures 2 and 3 in the discussion section.

Specific comments (written directly into the manuscript):

Comment line 28-33: “Not clair”

Thanks for the comment. We have made improvements to this paragraph to clarify our message, as follows:

Line 28-34: “Successful establishment of black spruce and jack pine depended upon regional conditions of precipitations and temperature, as well as on their interaction with stand-scale edaphic variables (surface deposit, drainage, slope) and local variables (micro-environmental) at the microsite-scale (establishment substrate types, substrate temperature). Mineral, organo- mineral and organic establishment substrates exerted mixed effects on seedling growth according to regional precipitations and temperature conditions and their interaction with edaphic and local variables at the stand and microsite-scales, respectively.”

Comment line 59: “I do not see the link between your experience and climat change”

We have made changes to the text to clarify the link between climate change and its influence on climate conditions and the establishment of trees, as follows:

Line 64-66: “…in the context of ongoing global change that will have significant effects on temperature and precipitation patterns and consequently, on the conditions for tree establishment trees [21–25].”

Comment line 67-69: “Should be more developped in the introduction to be understand here”

We have clarified our hypothesis as follows:

Line 73-75: “We tested the hypothesis that the effects of the establishment substrate leading to the highest growth rate depended on interactions between regional climate, edaphic and planting conditions across boreal Quebec.”

Comment line 80: “What was the age of the seedlings?”

Thank you for the comment. The seedlings were two years old when planted. We added this information in the text, in the methodology section:

Line 87-89: “In all cases, containerized seedlings were derived from local seed sources and produced in governmental nurseries over two years in 45-cavity containers (each with a volume of 110 cm³).”

Comment line 92: “The analyzed datas are base ont the measurements after 3 years following planting. But the measurements were taken at different years, so you have to treat this in the analysis and also you should mention it in the method part! Similar age is even more important in this kind of studies. Was the initial heigth and diameter mesured? Otherwise how did you adress this in your analysis?”

As mentioned earlier, the climate data we used as explaining variables corresponded to the 3-year growth periods specific to each plantations included in our dataset. Hence, our analyses of seedling growth are sound. Moreover, the use of data covering the 2011-2016 period (with matched seedling-climate data within that period) provides a larger gradient of conditions and thus, increase the inference potential of our study. Also, the use of RGR takes into account the potential initial differences in size between the seedlings. Please refer to our earlier responses for detailed changes that were made to the manuscript with regards of these comments.

Comment line 98: “Covering the three year analysis? Or only the last year of measurements?”

The climatic data collected (total precipitation and monthly temperatures) cover the three growing seasons of seedlings for each cutblocks planted with black spruce (between 2010 and 2016) and jack pine seedlings (between 2011 and 2016). This information is found in the methodology section:

Line 86-87: “Twenty-one cutblocks were reforested with black spruce between 2010 and 2016; eight cutblocks were reforested with jack pine between 2011 and 2016 (Figure 1)”

Line 120-121: “The climatic data were collected from May to September (growing season) during the first three growing seasons for each cutblocks;”

Comment on figure 1 “Change the symbols: for exemple, add a pattern for jack pine. It will be esier for the reader to distingish the two species”

We have modified the appearance of the study area map by enlarging the symbols representing the cutblocks. The figure already included different patterns distinguishing the two species: triangles for black spruce and circles for jack pine. The colors represent the different regions delineated using the climate data. These details are included in the figure caption and legend.

Comment Line 113-114 “Why only collect the data for the first growing season, when the diameter and height growth was measured over a 3 year period?”

Please, see our responses to comments 1 and 2 in the "General comments" section.

Also, we added more clarification in the methodology section of the text:

Line 98-99: “During the first three growing seasons on each site, data were collected at the microsite-scale for each seedling (≤ 1 m²): …”

Comment Line 132 “Base on what you division of your 4 groupes?”

We have improved this point by making the following changes and explanations in the text:

Line 142-149: “Last, we used medians of mean monthly temperature (13.5 °C) and total monthly precipitation (95.9 mm) as boundaries to delineate four groups: dry and cold region; wet and cold region; dry and warm region; and wet and warm region. The use of the median values of temperature and precipitation was more relevant than the mean values to delimit the four regions. Unlike mean value, the median value is relatively insensitive to outliers and detects the break point which can subdivide the data into several groups [32–34]. This subdivision method of data has already been successfully applied in ecology by previous studies [35,36]. Table 1 summarizes the number of black spruce and jack pine seedlings in each delineated region.”

Comment Line 139: “Add a table to show the number of analyzed plantes per groupe and microsite, there height, diameter + std values and other valuable information for the reader to have an idea of the data set into the analyzes”

As mentioned earlier, we added a table (new table 1) to present seedling height (cm) and collar diameter (mm) at the end of their 3rd growing season in the different regions of our study area. Please refer to our response to an earlier comment on the same topic.

Comment Line 142 “Add: by regrouping the regional scale, …”

These analyzes integrated all the data.

Comment Line 181 “Ones again: you should give information for the mean growth of the seedlings in a table. Thus, the reader can validate the results shown in figure 2 and 3.”

See our earlier response to a comment on the same topic (comment 10 in the "Specific comments" section)

Comment Line 191 “In table 1, we see the significant interaction between substate-type and precipitation. But humidity ou precipitation are not significant: how can you explain this?”

This interaction confirms our research hypothesis, which was that there are significant interactions between the environmental variables at different scales that drive early seedling growth. In other words, we posited that a given planting substrate would not have the same effect on early seedling growth depending on larger-scale environmental conditions. The lack of significant effects for a main treatment (e.g. precipitation) does not preclude the presence and interpretation of significant interaction effects (for example, see Steel, R.G.D., Torrie, J.H., and Dickey, D.A. 1997. Principles and Procedures of Statistics. A Biometrical Approach. 3rd ed. WCB/McGraw-Hill, Boston, MA.).

 

Comment Line 201 “Try to find a way to show this interaction with your figures (maybe larger signs for the important parametres).”

The PCA analyzes illustrated in figures 2 and 3, which have now been reorganized to represent the four climate regions, highlight the presence of interaction between variables at different scales (regional, stand and microsite scale).

Comment Line 211 “It looks logical, but the link to the figure has to be improve”

Please, see our responses to comments 4 et 14 in the "General comments" and “Specific comments” sections, respectively.

Comments Line 146 “You should add for seedling growth though out the paper. The relationships are probably different for mature trees.”

Done.

Author Response File: Author Response.docx

Reviewer 2 Report

The submitted manuscript entitled Regional climate, edaphic conditions and establishment substrates interact to influence initial growth of black spruce and jack pine planted in the boreal forest presents results of study on the influence of climatic and microhabitat conditions on establishment and growth of juvenile study tree species in different in humidity and temperature conditions. The research topic is very interesting and important from the ecological and economical point of view, because it concerns two common tree species in eastern Canada. However, in current form the manuscript is not suitable for publishing and needs major corrections.

The introduction should better introduce the reader to the research problem. It is not specified what problems occur when afforestation with Picea mariana and Pinus banksiana. It is also not explained why the study was conducted on these species and not on others.

The reader can only guess that it is because they are ecologically and/or economically important or problematic species in cultivation or all together. The hypothesis is trivial. I think that it should refer to knowledge of study species biology and differences between them. In the materials and methods, I did not find information about the origin of the plant material for afforestation. Did saplings come from local populations or from selected provenance/provenances? Please note that spruce in Quebec grows in very different climatic conditions. It can be expected that there are significant differences in adaptation to thermal and hydrological conditions between populations. This may affect the obtained results.  No criteria have been defined for the division into four habitat types (see Fig. 2 and 3). The detailed characteristics should be given. Statistics looks good. However, the obtained results rather confirm what was already known and do not contribute much to the knowledge about the cultivation and biology of the studied species. The conclusions are unconvincing (L.252-257).

 

Some specific comments:

L.6-1. The author’s affiliations are unformatted.

L.13-15 and L.40-45. Inaccurate and unnecessary information. Such data should refer specifically to the study species, not to all spruces and pines planted in Canada.

L.23. ‘planting beds’ -> Is it correct?

L.26. ‘effects of physical and climatic variables, and their interactions, on the establishment substrate’ –> It is unclear. It wasn't the subject of research

L.73. ‘mechanically prepared and reforested.’ -> This requires more explanation

L.98. ‘monthly averages.’ ->The approach seems good, but variability of meteorological conditions throughout the month is also important. The average data loses information on extreme conditions, e.g. late spring frost, which may be an important factor in the mortality of young trees.

L.222-223. This sentence should be rewritten.

Author Response

Dear Prof. Dr. Timothy A. Martin,

We thank you for the fast and thorough review of our manuscript. Please find attached the revised version entitled " Regional climate, edaphic conditions and establishment substrates interact to influence initial growth of black spruce and jack pine planted in the boreal forest". We thank the reviewers for their constructive comments. Based on their suggestions, we have significantly improved our manuscript, notably in the Introduction and Methods sections. You will find our additions and modifications in the main text, highlighted in yellow. Our point-by-point answers and comments are below, in blue.

 We hope you will find that this modified version is up to the high standards of Forests, and are looking forward to your decision.

Mohammed Henneb and co-authors

 

Reviewer 2

English language and style

( ) Extensive editing of English language and style required 
( ) Moderate English changes required 
( ) English language and style are fine/minor spell check required 
(x) I don't feel qualified to judge about the English language and style 

 

	Yes	Can be improved	Must be improved	Not applicable
Does the introduction provide sufficient background and include all relevant references?	( )	( )	(x)	( )
Is the research design appropriate?	( )	( )	(x)	( )
Are the methods adequately described?	( )	( )	(x)	( )
Are the results clearly presented?	( )	(x)	( )	( )
Are the conclusions supported by the results?	( )	( )	(x)	( )

General Comments

The introduction should better introduce the reader to the research problem. It is not specified what problems occur when afforestation with Picea mariana and Pinus banksiana. It is also not explained why the study was conducted on these species and not on others.

 

The reader can only guess that it is because they are ecologically and/or economically important or problematic species in cultivation or all together. 

Thank you for this comment. We have provided the following justification in the introduction section of the text:

Line 39-50: “The boreal forest of Eastern Canada remains a strong supplier of wood for both domestic and export markets. Indeed, the forest products industry is engaged in extensive harvesting and forest management activities across the region [1]. Softwoods, most notably spruces (Picea spp.) and pines (Pinus spp.), are among the main commercial species being logged for their lumber or wood fiber [2]. In Eastern Canada, reforestation operations complement natural regeneration to restore or maintain forest productivity, which would ensure continuous wood production that meets local and global demands [3]. Annually, about 175 million trees are planted in eastern Canada, across an area totalling about 100 000 ha [4]. In Quebec (Canada), black spruce (Picea mariana (Mill.) B.S.P.) and jack pine (Pinus banksiana Lamb.) represent 77% of the ~130 million seedlings planted in this province each year [5]. Although they can be found on similar sites in the boreal forest, jack pine is a shade-intolerant species with high potential rates of resource capture relative to black spruce, which is a shade tolerant species adapted to low-resource environments [6].”

The hypothesis is trivial. I think that it should refer to knowledge of study species biology and differences between them.

Please, see our response to comments 3 of the Reviewer 1 in the "General comments" section, which as been rephrased as:

Line 73-75: “We tested the hypothesis that the effects of the establishment substrate leading to the highest growth rate depended on interactions between regional climate, edaphic and planting conditions across boreal Quebec.”

 

In the materials and methods, I did not find information about the origin of the plant material for afforestation. Did saplings come from local populations or from selected provenance/provenances?

Thank you for this comment. We have added information in the text to specify the origin of the seedlings:

Line 86-89: “Twenty-one cutblocks were reforested with black spruce between 2010 and 2016; eight cutblocks were reforested with jack pine between 2011 and 2016 (Figure 1). In all cases, containerized seedlings were derived from local seed sources and produced in governmental nurseries over two years in 45-cavity containers (each with a volume of 110 cm³).”

Please note that spruce in Quebec grows in very different climatic conditions. It can be expected that there are significant differences in adaptation to thermal and hydrological conditions between populations. This may affect the obtained results

In Quebec, seedlings for reforestation are produced from seed sources that reflect the regional climate conditions of the sites where planting is to occur. Our study, which was based on the sampling of operational plantations distributed across a portion of boreal Quebec, reflects the performance that is to be expected from regular forestry activities. Although we agree that would be interesting to evaluate genetics driver of seedling performance in the different conditions we have sampled, this is beyond the scope of our study. Moreover, Benomar et al. (2016. Front Plant Sci 7: 48) have shown that seedling height after two years did not vary significantly between spruce seedlings produced from seed sources that were thousands of km apart; planting site was the main factor driving seedling response.

No criteria have been defined for the division into four habitat types (see Fig. 2 and 3). The detailed characteristics should be given.

Please, see our response to comments 9 of the Reviewer 1 in the "specific comments" section.

Statistics looks good. However, the obtained results rather confirm what was already known and do not contribute much to the knowledge about the cultivation and biology of the studied species. The conclusions are unconvincing (L.252-257)

Our study provides new knowledge on the influence of multi-scale environmental variables on the effect of substrate on initial growth of black spruce and jack pine seedlings. Our study provides significant knew knowledge that can directly influence plantation silviculture in Quebec. We show, for the first time, how the best planting substrate for successful seedling establishment varies across region and species.

Specific comments

6-1. The author’s affiliations are unformatted.

We used and review again the Forests Review Template to format the authors' affiliations.

13-15 and L.40-45. Inaccurate and unnecessary information. Such data should refer specifically to the study species, not to all spruces and pines planted in Canada.

Thank you for this comment. We have added the following changes to the text:

Line 13-15: “In eastern Canada, spruces (Picea spp.) and pines (Pinus spp.), are among the main commercial species being logged for their lumber or wood fiber. Annually, about 175 million seedlings are planted in areas totalling ~100 000 ha.”

Line 41-42: “Softwoods, most notably spruces (Picea spp.) and pines (Pinus spp.), are among the main commercial species being logged for their lumber or wood fiber [2].”

23. ‘planting beds’ -> Is it correct?

Corrected. We replaced "planting beds" by "cutblocks" in the ms:

Line 23: “Substrate characterization and growth monitoring (3 growing seasons) for the two species were conducted on 29 planted cutblocks that were distributed over an east-west climatic gradient (precipitation and temperature), particularly in the balsam fir and black spruce-feather moss forests of Quebec (Canada).”

26. ‘effects of physical and climatic variables, and their interactions, on the establishment substrate’ –> It is unclear. It wasn't the subject of research

Thank you for the comment. We have modified the text as follows:

Line 25-27: “Linear mixed models and multivariate analyses (PCAs) determined the effects of climatic, edaphic, micro-environnemental variables and their interactions, on the establishment substrate and seedling initial growth.”

73. ‘mechanically prepared and reforested.’ -> This requires more explanation

Done. We have added the following explanations:

Line 78-79: “We used data that were collected from 29 operational cutblocks (average area: 8.5 ha) that had been submitted to mechanical site preparation and planted.”

98. ‘monthly averages.’ ->The approach seems good, but variability of meteorological conditions throughout the month is also important. The average data loses information on extreme conditions, e.g. late spring frost, which may be an important factor in the mortality of young trees.

This is an interesting comment. However, we focussed our study on seedling growth rather than on survival and thus restricted our analyses to living seedlings. In addition, the extreme values of temperature and precipitation were included in the calculation of the monthly averages.

222-223. This sentence should be rewritten.

Done. The sentence has been modified as follows:

Line 241-242: “The growth of black spruce seedlings is positively related to increasing temperature [57–59], but only up to a certain limit above which physiological processes are negatively affected [60,61].”

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Overall, I agree with the changes made on the paper. The Table 1 and the figures have been improved (in despite that figures 2 and 3 are still difficult to read).

With regard to the improved figure 1, I noticed that only 1 black spruce site is located in the wet-warm region and 1 Jack pine site in the dry-cold region. How can you be sure that these seedlings from both sites are representative for the climatic zone? You should at least address this issue in the discussion part. Also, does the unbalance number of measured seedlings per climatic zone create a bias on the statistical analysis?

Author Response

Reviewer 1

General Comments

Overall, I agree with the changes made on the paper. The Table 1 and the figures have been improved (in despite that figures 2 and 3 are still difficult to read).

Thank you for this comment. We are glad that our efforts in addressing the previous round of comments were successful. We have modified the appearance of the figures (2 and 3) by enlarging the size of the font and symbols. Refer to figures 2 and 3 in the revised manuscript.

With regard to the improved figure 1, I noticed that only 1 black spruce site is located in the wet-warm region and 1 Jack pine site in the dry-cold region. How can you be sure that these seedlings from both sites are representative for the climatic zone? You should at least address this issue in the discussion part. Also, does the unbalance number of measured seedlings per climatic zone create a bias on the statistical analysis?

The spatial distribution of the plots in the boreal forest of Quebec was dependent on operational management planning and reforestation activities during the corresponding years, combined with constraints related to plot establishment in remote areas. Our experimental design reflect these constraints and our mixed model was parametrized to take into account-unbalanced data. Although we are confident that our sampling adequately represents the reforestation context of boreal Quebec, we acknowledge that some regions are less represented, compared to other ones. For this reason, our study is ongoing and more plots are being established and revisited to balance the sampling. Although the short-term results we are presenting here are eagerly awaited by silviculturists and forest managers, long-term follow-up that will include a larger set of plots will enable verifying our first conclusions. We have added a few short sentences at the end of the "Conclusion" section to clarify this point:

Line 298-303: “Some regions had fewer plots than others did, as distribution of the plots was dependent on operational management planning and reforestation activities during the corresponding years, combined with constraints related to plot establishment in remote areas. Our study is ongoing, with new plots being added in new plantations across the entire study area to better balance the design. Further measurements and analyses that will include a larger set of plots will thus allow confirming the robustness of our first conclusions.”

Reviewer 2 Report

The submitted manuscript entitled ‘Regional climate, edaphic conditions and establishment substrates interact to influence initial growth of black spruce and jack pine planted in the boreal forest’ has ben significantly improved by authors. All necessary information were completed. I’m also satisfied with author’s responses to my comments. However, some minor corrections are needed before publishing the manuscript in Forests journal.

 

Specific comments:

L.7-11. Authors initials should be added in brackets to affiliations.

Plant names and authors abbreviations should be given according IPNI www.ipni.org.

Picea mariana (Mill.) B.S.P. ->Picea mariana Britton, Sterns & Poggenb.

Abies balsamea [L.] Mill.-> Abies balsamea (L.) Mill. - square brackets should be replaced with ‘regular ones’

L.35. Black spruce and jack pine should be removed from the key words

L.50. low-resource environments -> pure in nutrients soils?

L.107-111. The division into climatic regions and vegetation zones looks different according to different authors. The source of the map presented in Figure 1 should be given.

125. If any special R packages were used for analysis, they should be listed and cited here.

Author Response

Reviewer 2

The submitted manuscript entitled ‘Regional climate, edaphic conditions and establishment substrates interact to influence initial growth of black spruce and jack pine planted in the boreal forest’ has ben significantly improved by authors. All necessary information were completed. I’m also satisfied with author’s responses to my comments. However, some minor corrections are needed before publishing the manuscript in Forests journal.

Specific Comments

7-11. Authors initials should be added in brackets to affiliations.

The authors' affiliations have been formatted according to the requirements of Forests, exactly as they were presented in this recent article published in Forests: https://www.mdpi.com/1999-4907/11/1/120.

Plant names and authors abbreviations should be given according IPNI www.ipni.org.

 

Picea mariana (Mill.) B.S.P. ->Picea mariana Britton, Sterns & Poggenb.

 

Abies balsamea [L.] Mill.-> Abies balsamea (L.) Mill. - square brackets should be replaced with ‘regular ones’

We have made the requested corrections to the names. We also checked and corrected the names of all plant species mentioned in the text:

Line 21-22: “…initial growth of black spruce (Picea mariana Britton, Sterns & Poggenb) and jack pine (Pinus banksiana Lamb.).”

Line 47-48: “In Quebec (Canada), black spruce (Picea mariana Britton, Sterns & Poggenb) and jack pine (Pinus banksiana Lamb.)”

Line 73-74: “These plantations were established in the balsam fir (Abies balsamea (L.) Mill.) and spruce-moss bioclimatic domains of boreal Quebec (Canada)”

Line 82-85: “The balsam fir domain is dominated by mixed stands of yellow birch (Betula alleghaniensis Britton), paper or white birch (Betula papyrifera Marshall), and softwoods such as balsam fir, white spruce (Picea glauca (Moench) Voss) and white cedar (Thuja occidentalis L.) [26].”

35. Black spruce and jack pine should be removed from the key words

We removed Black spruce and Jack pine from the key words. In addition, we added "seedling growth" in the key words.

50. low-resource environments -> pure in nutrients soils?

We suggest keeping the expression “low-resource environments”, as it encompasses more things than just nutrients. (nutrient, water, temperature…).

107-111. The division into climatic regions and vegetation zones looks different according to different authors. The source of the map presented in Figure 1 should be given

We have added a citation for the bioclimatic regions we are refeering to in the figure. See reference 26 in the list of references: “Saucier, J.P.; Robitaille, A.; Grondin, P. Cadre bioclimatique du Québec. In Manuel de foresterie; Editions Multimondes, 2009; pp. 186–205.”

Line 108-112: “Figure 1. Location of permanent inventory plots distributed in cutblocks planted with black spruce (BS, filled triangles) and jack pine (JP, filled circles) in the balsam fir (grey areas) and spruce-moss (white area) bioclimatic domains of boreal Quebec, Canada [26]. Plots are located in four regions that were delineated based on their precipitation and temperature regimes (different coloured symbols). The regions are Dry-Cold, Dry-Warm, Wet-Cold and Wet-Warm.”

If any special R packages were used for analysis, they should be listed and cited here.

The R packages used for our analysis under R were already cited, notably the lme4 package for mixed model fitting and running.

Line 134-136: “The geographical distribution (longitude and latitude) of the plots were considered random effects in the model, which was fitted using the lme4 library [31].”

Author Response File: Author Response.pdf