The study “Radial growth of Picea abies is controlled by joint effects of temperature and nutrient availability at the lower part of treeline ecotone” compared growth phenology of Picea abies tree growth at the opposite slope aspect (North-facing and South-facing) which are considered to have contrasting soil nutrient dynamics. The study claimed that temperature governs the growth phenology of these species, but ambiguously conclude that nutrient availability modulate the growth rate during the peak growing season. I partly agree with these conclusion due to following reasons:

1. Since the study only considered single site at each slopes (N-facing and S-facing), the result cannot be generalized, particularly in the mountain landscapes with higher influence of microclimates. Please clarify these issues.
2. There is no any statistical analysis to support the conclusion that soil nutrients drive/modulate their growth.
3. Precipitation is considered to play a major role in soil formation and development and also tree growth (also mentioned in line 37-39), particularly in the alpine treeline ecotone. However, variation in precipitation between two study sites has not been mentioned. These sites may exhibit difference in precipitation (e.g. windward/leeward effects), which has been largely ignored. At least, soil moisture will be largely different between North-facing and South-facing slope aspects. There are more references on topography-dependent growth responses in the mountain regions. Please clarify.
4. The authors mentioned that soil samples collected during two field campaign (2012-2014 and 2023) were merged to determine soil nutrients, which for me seems to be random.
5. In my understanding, Picea abies as a dark forest species, and cannot survive in sunny and south-facing slope. Based on the landscape photo in Fig. 2, it may be not fully source facing slope (east-south or west-south), or the slope is strongly influenced by shade of surroundings, thus have a shade-like environment for spruce forest.

Other comments

In my opinion, there is no strong evidence to state that “Radial growth of Picea abies is controlled by joint effects of temperature and nutrient availability at the lower part of treeline ecotone”. Thus, the title seems to be more ambiguous.

Please clarify the term “lower part of treeline ecotone”. It is confusing to me. For the landscape photo, it is not clear whether there is climatic treeline or not in your research sites. It looks to be that trees almost cover the mountain top.

The hypotheses mentioned in abstract and introduction are different.

In the methodology section, it was mentioned that Kruskal-Wallis test was conducted to investigate the difference in measured soil variables between two sites. Did you find significant difference between sites? Why are their significance not included in the result section and figures? Not only for soil but also for all other variables.

Which chronology (standard?) was used for the climate-growth relationships? Also, please provide the statistics of the chronology, at least in the supplementary information.

Please check for Picea abies and make it consistent throughout the text (Italic).

There are many long sentences with a lot of repetition, which is difficult and tedious to follow. This issue should be carefully revised.

Based on line 97-99, Line 11 “…..contrasting sites located on north and south-facing slopes…..” is not true.

Line 254: I suggest not to use the phrase “it is worth mentioning……” here.

Line 289: may not be true.

Line 300: also see recent work:

Li, et al. 2023. National Science Review 10, nwad182, https://doi.org/10.1093/nsr/nwad182 

Line 302-304, Long sentence with repetition.

Line 306: Clarify the term “systematically”

Line 311: Why are there no any references for nutrients?

Line 312-315 It is very difficult to follow.

Line 367. I suggest to delete “which lags behind the pace of warming”.

The manuscript “Radial growth of Picea abies is controlled by join effects of temperature and nutrient availability at the lower part of treeline ecotone” by H. Kuželová et al. provides insights in the treeline ecotone dynamics linked to climate and soil nutrient availability. The authors were able to show that soil conditions can play a crucial role in influencing the radial growth of trees and mitigating the impact of solar radiation, which varies significantly in mountainous environments depending on the slope's exposure. Many studies in dendroecology do not consider soil variables (temperature, humidity, and nutrients), and this work stimulate to include these parameters to better understand growth dynamics at landscape and regional scales. Below comments and suggestions that could help to improve the manuscript.

Main comment 1:

The justification for selecting the lower part of the treeline for data collection in your experimental design remains unclear. In various sections of the manuscript, including the title, specific reference is made to “the lower part of the treeline ecotone”. The reasons your hypotheses are only applicable to trees within this elevation zone are not specified. The introduction should provide justification for choosing this specific area of the treeline and explain why it is more suitable for conducting the study.

Main comment 2:

The ring-width chronologies have not been sufficiently exploited in the study. Only the results of the correlations between climate and growth have been shown. There is a lack of basic statistics of the chronologies, such as average ring width (or average basal area increment), maximum and average age, serial intercorrelation, mean sensitivity etc. Average basal area increments can be better analysed by comparing the long growth series (100 years?) of the 60 samples taken from north and south sites rather than only the 16 trees (3 cambial years) sampled with Trephor. 

Main comment 3:

The estimation of insolation on each site does not consider cloud cover. The discussions lack a section indicating the potential influence of this factor. The results of the correlations between climate and growth show a negative relationship with precipitation in the period DOY 115-125. This relationship is not discussed in the article. The relationship could be due to the negative effect of cloud cover (associated with precipitation), which makes photosynthetic activity less efficient at the beginning of the vegetative period.

Minor comments:

L 9-10: see main comment 1.

L14-16: Please rephrase this sentence.

L 78-79 & L 88: Species names in italic.

L 95-96: Is Picea abies the only tree species at the treeline?

Figure 1: Consider moving Figure 1C and 1D in the results section. You explain how you obtain this graph in M&M (ll 121-123).

L 119-120: Please specify if you consider continuous period or not.

l 136: Please specify if these six trees are the same sampled with Trephor.   

L 193: “standardization”.

L 201&210: “°C” instead of “K”.

Table 1: Indicate the unit for degree days.

L294: See main comment 3. It's not clear what is meant by 'entire lifespan of trees' (2012-2014 period or 1961-2013 period?).