Review Reports

Round  1

Reviewer 1 Report

In the manuscript “The spatial distribution of the needle area of planted Larix olgensis trees” authors aims to examine the vertical and horizontal distribution of needle area (NA) within the crowns of Larix olgensis trees is described with a two-dimensional NA model. I made comments in each section, where authors can consider revising manuscript accordingly.

Abstract: State objectives clearly in the abstract

Introduction: Introduction has given good background information on different foliar distribution models and the objectives. It is useful to include a paragraph on taxonomical states of Larix olgensis, since the study solely focused on the species. Some ecological details on the species has given in the first paragraph of the Materials and Methods (L 80-90), which can move to the introduction. However, geographical distributional information of the species can couple with site description in the methods.

Materials and Methods: This is a good section with subheadings and equations.

Line 108 & Line 114: AZI refers to azimuth, which is one word. Generally, acronym creates from a phrase, which probably can consider relative azimuth of neighboring trees (RAN/RAT)  

Line 109: Is that DIS refereeing to distance? I did not see “DIS” use in the main text.

Results: Good section with interesting results

Line 200: Give full name for RDINC before acronym (“relative depth into crown” L 207)

Line 217 If significant give P value here

Discussion: The discussion begins with a summary of different methods that used for foliar estimation and highlighting the importance of the present method, which makes sense. The authors compare their results with others giving some figures. So this section is well written.

Line 314: What does NPB stands for?

Line 364: Tsuga heterophylla

Minor comments are given in the attached .pdf.

Comments for author File: Comments.pdf

Author Response

see Word file

Author Response File: Author Response.docx

Reviewer 2 Report

General comments

Authors analyzed spatial distribution (vertical and horizontal distributions and their cumulative needle area distributions) using the Weibull distribution function. The two-dimensional needle area model was also established by combining the two Weibull distribution functions of the vertical and horizontal distributions. Three destructively sampled trees in three sample plots, each one from every plot was used as a focal tree and other neighboring trees were used as potential competitors for a focal tree. Authors measured needle area and needle mass for each focal tree. Based on authors’ analyses, there were significant variations of needle area and needle mass distribution patterns within the same trees in different directions in the crown and differences among three focal trees. Authors concluded that such differences may be due to the competition impact from the neighboring trees, which was mainly for making the available for them. Manuscript is written well in general regardless of the appropriateness in the methods used. The results of this study may be useful for formulating the silviculture strategies for forest management decision-making. Manuscript intends to provide a new knowledge to the readers (though similar studies have already been carried out for other species) therefore, has a reasonable merit for publication with Forests. However, following major issues should be addressed before it goes for getting published.   

Major issues  

1)      One of the main focuses of this study should have been given to the crown competition index (CCI), as this is a measure of the major driving force (competitive interactions) to make the variations of the needle area and needle mass in the focal trees. However, authors did not consider this as main issue in their study, and have not described properly how they calculated CCI. One reference provided for CCI therein is in Chinese, and therefore it is not readable to the international readers. Thus, details of the CCI should be presented in the methods. The description includes:

Methods and formulae used for CCI calculation

Which criteria (horizontal or vertical search angle-based criteria) were    used to identify the potential competitors for each focal tree

What correction factors (edge bias compensation or linear expansion factor) and how it was applied for the off-plot competitors, if any

2)      Table 1 shows that there 3, 6 and 7 competitors for each focal tree of each sample of size 20 mx 30 m. Given the stand density per ha in line 102, this size of sample plot means there should be 120, 144, and 192 trees for plot 1, 2, and 3, respectively. But authors listed 3, 6 and 7 competitors for each sample plot. It means that no other potential competitors would exist. How was this confirmed objectively? This must be provided in the methods. I assumed more trees might be competitors, but it depends on criteria of identifying competitors.

3)      It is also not mentioned about the location of focal tree inside the sample plot, thus I suggest to show the location of focal tree on each sample plot together with those competition in the pictorial form. It would be possible to do so as coordinates of each trees have been recorded.

4)      Authors decided to use CCI, i.e. competition measure estimated based on crown dimensions of focal tree and its competitors. Why only this decision? Why not you evaluate other types of competition indices that are based on other tree dimensions, such as DBH and height. So better to evaluate all types of competition indices and select the best performing one.   

5)      Even though results are interesting, any implication of the results in silviculture and forest management is completely lacking in the manuscript. Thus, potential implications must be described in the manuscript, so that readers of Forests will become happy with your article.

Minor issues

Line 10-12: numbers of focal trees and sample plots should be provided.

Line 62-78: What hypothesis you may assume for your study? Would be better if you give somewhere within here.

In Table 1: please delete “mean” for CW, as it makes confusion that it is a mean of all trees, especially in the right part “neighboring trees”. Yes, it is a mean of four CWs for a tree, but creates confusion. But mention what is it? arithmetic mean or geometric mean in the text, but not in Table. Please also provide CL or CR information of each tree, and Dg and BA per ha need to be presented in the table as well.

Line 117: how height to crown base (base of live crown) was defined here, please make clearer.

Line 124: Please replace hypothesize with assume, as you have not evaluated this hypothesis in your analysis.

Line 127: 105 degree centigrade might be too much intense heat for needle drying. If done so, how long samples were kept in the dryer under this temperature to get the constant weight that was used for determining RDF? More detail information about drying process is needed here.  

Line 153-155: Not much clear: You mean, grouping is 315-45: N; 45-135: E; 135-225: S; 225-315: W, where lower or upper boundary is excluded in each group, isn’t it?

Line 150 or each of the other equations elsewhere, please define each symbol, letter, and abbreviation after equation, so that readers don’t need to search those in other places of the article.

Line 178: these coefficients are not estimated yet, so better to write “to be estimated”.

Line 182: Validation is something different, did you validate your estimated model using independent data? No, so please be careful using this term, better to use term, “evaluation”.

Lines 197, 203: please provide p-vale or any other test statistical value here.

Line 318-323: Most part of this should fit to the method section, so better to move there.

Line 331: I don’t think so, but compared to the trees in other plots, competition may be lower, but it depends on several factors. 120 trees are also many trees on this plot, so competition may be intense.

Author Response

see Word file

Author Response File: Author Response.docx

Round  2

Reviewer 2 Report

General issues

 I would thank authors for addressing all issues, except one, raised in my previous review. I agree with authors’ idea to identify the potential competitors for each target tree. However, I need more clarification whether authors have applied the correct methods of estimating crown competition index (CCI), because it is not properly described in the revision, even a given formula (Eq. 1) is not clear. Thus, this has given me suspicion that whether CCI was calculated correctly. Authors used a ratio of crown projection area of competitor i and that of a target tree t, i.e., CS_i /CS_t was multiplied by inverse of the inter-tree distance 1/DST, which is theoretically correct, but CCI obtained with this formula is due to a single competitor tree i (i=1,2,…..n, where n is number of competitors). Total competition impact experienced by a target tree should therefore be a sum of CCI of all trees exerting competitive stress to the target tree. Therefore, authors should make a sum of CCI of all competitor trees for every target tree. The correct formula for this can be,

 CCI =sum (CS_i /CS_t)*1/DCT

Authors used a ratio of crown projection area of competitor i and that of a target tree t, which is unclear whether they have used ratio of crown projection areas of a competitor and target tree or used total crown projection areas for ratio calculation. If former was used, it was wrong; authors should have considered the letter ratio as only overlapped part is responsible for contributing to the competition stress to the target tree. Authors may follow Pretzsch et al. (2002) for calculation of CCI. Authors should address these two issues while making their revision works. This may need some minor works and minor changes in the method, and may be in the results too, if authors have calculated CCI wrongly using a presented formula, which is not also clearly defined.  

Reference

Pretzsch et al. (2002). The single tree-based stand simulator SILVA: construction, application and evaluation. Forest Ecology and Management 162:3-21.

Author Response

see the word file.

Author Response File: Author Response.docx