Climate Adaptation in White Oak (Quercus alba, L.): A Forty-Year Study of Growth and Phenology
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors2024-01-09
Review of the manuscript: “Climate Adaptation in White Oak (Quercus alba, L.): A Forty-Year Study of Growth and Phenology”
In light of global climate changes, the consideration of both phenotypic and genetic factors becomes crucial, especially in the context of assisted migration of tree species. In conservative sylviculture, it is postulated that seeds used for forest regeneration should originate from local seed stands. It is expected that the success performance of plantation originated from local seed sources will be high because the local genotype is better adapted to the local site conditions than the provenances originated from geographically distant seed stands. Under global climate change, however, this conservative rule has been undermined due to maladaptation of some species to increasing temperatures accompanied by drought. Assisted migration, i.e. the transfer of seeds from the southern part of the species geographical range to north is regarded as a way to increase the ability of the species to adapt faster to global warming. Economically important forest tree species, especially those with the large geographical range, often have the ecotypes adapted to the local site conditions. The phenotypic and genetic intraspecific variation of forest trees have been, however, less studied than the interspecific variation. The manuscript reports results of the Q. alba provenance trial showing differences in phenology and growth among the provenances which can be crucial for this species response to global warming.
The phenological observations and measurements of growth and survival were conducted in common garden planting with 6 provenances of white oak. The main aim of this study was to answer the question about growth and phenological plasticity of this economically important species along the geographical gradient. There were significant differences in phenology and growth among the study provenances with southern ones showing faster growth and later senescence relative to seed sources.
The experiment in common garden was well designed, however, the number of provenances was low, and rather not representative for the whole range of Q. alba. The question can be addressed why these provenances were selected and not some others? On the other hand, an advantage of this study was the relatively long period of growing trees in common garden (40 years) and long-lasting observations that would have been difficult to conduct having a higher number of provenances.
An interesting result indicates that the study provenances growing season length were driven primarily by fall senescence due to the greater variability in fall phenology compared with bud-break in spring. As it can be expected, the northern provenances have shown adaptation to the shorter vegetative season than the southern provenances. The adaptation to the shorter vegetative season can be regarded as maladaptation to the future climate. The differences in growth dynamics and mortality among the provenances also suggest that the selection of provenances which can better cope with global warming will be possible, however, the provenance trials with the same provenances should be situated in several localities. The conclusion that “By sourcing trees from warmer locations…, white oak plantings will be tolerant of current and likely future conditions” is supported by the results of this study, however, it is risky and arguable. Long-lived trees are characterized by changing tolerance to site conditions depending on their age. Results of assisted migration depend on geographical distance, many abiotic factors, not only increasing temperatures, but also biotic factors which may limit growth and development of trees after their transfer to the new environment. Additionally, bioclimatic models even when supported by genetic data have not been perfect.
The present manuscript provides the new insights into growth and phenology of Q. alba. The results are important for forest ecology and management and can be applied in sylvicultural practice. The manuscript is well written, results are clearly presented and support the conclusion. I recommend this manuscript to be published in “Forests” after a minor revision. This revision should answer why these specific provenances were used in the trial.
There is a small concern:
The captions of figures 1, 2, 3 and 4 lack the number of replications.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsTo improve the understanding of the results and conclusions, the authors should incorporate the following aspects into the text.
+ In experimental design (lines 86 to 94), there are 6 random blocks with 4 trees each according to 6 provenance (144 pl.). But the plant number is 218 (12 rows x 18 columns). I understand that they have considered the 6 provenance and in 2 of them (Indiana and Illinois) the particular locations (2 and 3 respectively) to reach 9 real provenances. Later throughout the text, they only talk about data, results, etc. from 6 provenances. How they have used data from Indiana and Illinois should be clarified.
+ In the text lacks a minimum of information or description about climatic conditions of the seed provenance areas and especially from the experimental plot location.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript with the title "Climate Adaptation in White Oak (Quercus alba, L.): A Forty-Year Study of Growth and Phenology" presents a study that examines the performance of white oak (Quercus alba, L.) across a range of provenances in a southern Indiana common garden planting, focusing on the species' response to climatic variables and the potential role of assisted migration in forest management. The paper takes a worthy topic, the structure is strong, and it is technically correct. I only have some questions about the methodological approach followed:
a) first, are all the provenances sharing the same climatic and edaphic conditions? It would be nice to include the data to know how different the conditions of the provenances are and if they could explain the results found. As the title suggests ("Climate adaptation.."), it is important to know the conditions and
b) As the authors stated, the start of the growing season was assumed to be when the temperature reached 10 C; therefore, I must assume that water availability was not an issue. Am I wrong?
c) Lines 121-122. It assumed that the trees were already adapted to the climate or why the spring leaf budbursts were recorded in 2022 (year 39) 121
and 2023 (year 40) only?
d) I found this study very interesting, especially because of the insights and valuable information that suggest that assisted migration will help to ensure future forest ecosystems' viability and productivity. Therefore, I would like to see a more robust discussion and some references to support/contrast the author's findings.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe text is now ok.
Author Response
Excellent. Thank you for your input on improving the manuscript.
