Comparison of Spatially and Nonspatially Explicit Nonlinear Mixed Effects Models for Norway Spruce Individual Tree Growth under Single-Tree Selection

Round 1

Reviewer 1 Report

The submitted paper is state-of-the-art of basal area increment modelling and the relevant literature was carefully read and cited. Description of data, methods and results are clear, and well visualized. Fitting of models for selection forest systems with two thinning interventions are very rare and the authors could demonstrate, that height based competition indices perform better for this silvicultural management and would better link to remote sensing data. Also periodic thinning effects are well-demonstrated and studies showing thinning effects are rare.

Authors might want to additionally discuss, if height based measures would also be superior in even-aged stands, where there is little variation between tree heights. Generally the results obtained are also in agreement with previous studies, with very small or no differences of spatial and non-spatial indices for tree growth predictions. In this study, however I do see some added value in including spatial components and this is for the prediction of thinning response. In my opinion the spatial response seems more logical, but this needs to be verified. A possible reference could be Bevilaqua et al. 2005.

Bevilacqua, E., Puttock, D., Blake, T.J., Burgess, D., 2005. Long-term differential stem growth response in mature eastern white pine following release from competition. Can. J. For. Res. 35 (3), 511–520. https://doi.org/10.1139/x04-198.

Minor comments:

 

Line 59: Individual tree growth patterns often continuosly increase with size see reference; the exponential model from chosen would fit such patterns. – so they are not sigmoid.

Stephenson, N.L., Das, A.J., Condit, R., Russo, S.E., Baker, P.J., Beckman, N.G., Coomes, D.A., Lines, E.R., Morris, W.K., Rüger, N., ´Alvarez, E., Blundo, C., Bunyavejchewin, S., Chuyong, G., Davies, S.J., Duque, ´A., Ewango, C.N., Flores, O., Franklin, J.F., Grau, H.R., Hao, Z., Harmon, M.E., Hubbell, S.P., Kenfack, D., Lin, Y., Makana, J.-R., Malizia, A., Malizia, L.R., Pabst, R.J., Pongpattananurak, N., Su, S.-H., Sun, I.-F., Tan, S., Thomas, D., van Mantgem, P.J., Wang, X., Wiser, S.K., Zavala, M. A., 2014. Rate of tree carbon accumulation increases continuously with tree size. Nature 507, 90–93. https://doi.org/10.1038/nature12914.

Line 84-85 – Quite abrupt jump between topics between the paragraphs

Line 168: Competition indices caluculated in local neighbourhood are often also referred to as semi-spatial competition indices

Line 209-211: This is not clear to me, please revise

Line 214: were missing? Please check

Line 248-249: Delete either „following“ or „respectively“

Line 249: Please check equation numbering

Line 343: Please shortly eyplain why Voronoi polygons were not used

Line 354: Yes, but the results might only hold for structurally diverse forests

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The reviewed manuscript is interesting since it raises a very important issue of basal area growth model in uneven-aged Norway spruce dominated forests in southern Finland that have been managed by the single-tree selection system for almost 30 years.

The main objective of this study was to compare the performances of spatial versus non-spatial approaches for Norway spruce individual tree growth modeling using non-linear mixed models. The issue of these two different approaches is significant from the practical point of view. These two approaches require various workloads and differ in time-consuming. The spatial and diameter-based approach needs more time and effort than the non-spatial and height-based one with using UAV.

In my opinion, the topic is also important for proper management of uneven-aged stands. There is a need to develop the appropriate growth models fitted to the specific site and stand conditions. The manuscript is a step forward in that process.

However, I found a few minor shortcomings that could be easily corrected and improving the text style:

Line 104: the word "often" appears two times in the sentence. Please delete one.

Table 1: I am not sure if the average values are necessary here. Within such a structure mean values that don't give any information should be changed to median or modes.

Line 249-250: The numbering of equations should be changed to "3" and "4"

Figure 4: In the caption of the figure - All data is shown on the top left not right plot. In the same sentence, the top left plot refers to the spatial or non-spatial model?. It is not clear.

Line 365: In my opinion, the fragment "....from their Figure 3 (dominant thinnings) that..." should be removed from the manuscript since readers don't see that figure during the reading text.

Author Response

Please see the attachment

Author Response File: Author Response.docx