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Peer review report 2 On “Environmental-mediated relationships between tree growth of black spruce and abundance of spruce budworm along a latitudinal transect in Quebec, Canada”
Agricultural and Forest Meteorology 217 (2016) 145
Contents lists available at ScienceDirect
Agricultural and Forest Meteorology journal homepage: www.elsevier.com/locate/agrformet
Peer Review Report
Peer review report 2 On “Environmental-mediated relationships between tree growth of black spruce and abundance of spruce budworm along a latitudinal transect in Quebec, Canada”
1. Original Submission 1.1. Recommendation Revision 2. Comments to Author: The manuscript presents new tree ring data providing a history of black spruce growth and examines relationships between spruce growth and interpolated weather data and simulated spruce budworm data. Below, I provide a set of questions and recommendations for improving the manuscript. 1. One of my main concerns is that the authors are making conclusions about the effects of spruce budworm (SBW) outbreaks on tree growth without actual data on SBW densities. Instead, the authors are using predictions of SBW densities obtained from a physiological model of seasonality. Though models of this type do a good job of predicting insect phenology, I do not believe they can provide reliable predictions of insect density. Annual variation in insect density is notoriously difficult to predict given the presence of stochasticity and the complexity of factors involved including interactions of abiotic and biotic factors (e.g., interactions with natural enemies).
DOI of original article: http://dx.doi.org/10.1016/j.agrformet.2015.06.014. 0168-1923/$ – see front matter http://dx.doi.org/10.1016/j.agrformet.2016.01.064
2. In the absence of data on SBW densities, I am not sure how they can separate the effects of herbivory from the effects of weather on tree ring widths. It is standard practice in dendrochronology to remove the climate signal from the host tree ring time series using a non-host tree ring time series. However, it does not appear the authors measured tree ring growth in any non-host tree species. 3. Regarding the statistical analyses, the authors did not explain whether they accounted for temporal autocorrelation in their data when conducting significance tests (e.g., cross-correlations, Mann Kendall tests for trends). If they did not account for autocorrelation, the results are biased towards type-I error. Similarly, in at least one case (Figure 3), the authors conducted a large number of nonindependent hypothesis tests but they did not appear to correct for inflated type-I error resulting from these non-independent tests. 4. In general, the manuscript seems to overemphasize the role of climate in defoliator outbreaks. I am skeptical that climate alone can explain why an insect population might cycle (i.e., oscillate at a regular interval). This type of population behavior is widely thought to require delayed density dependence due to biotic influences (e.g., specialist natural enemies). 5. The overall clarity of the writing throughout the manuscript should be improved. Many sentences are difficult to understand. Anonymous
Contents lists available at ScienceDirect
Agricultural and Forest Meteorology journal homepage: www.elsevier.com/locate/agrformet
Peer Review Report
Peer review report 2 On “Environmental-mediated relationships between tree growth of black spruce and abundance of spruce budworm along a latitudinal transect in Quebec, Canada”
1. Original Submission 1.1. Recommendation Revision 2. Comments to Author: The manuscript presents new tree ring data providing a history of black spruce growth and examines relationships between spruce growth and interpolated weather data and simulated spruce budworm data. Below, I provide a set of questions and recommendations for improving the manuscript. 1. One of my main concerns is that the authors are making conclusions about the effects of spruce budworm (SBW) outbreaks on tree growth without actual data on SBW densities. Instead, the authors are using predictions of SBW densities obtained from a physiological model of seasonality. Though models of this type do a good job of predicting insect phenology, I do not believe they can provide reliable predictions of insect density. Annual variation in insect density is notoriously difficult to predict given the presence of stochasticity and the complexity of factors involved including interactions of abiotic and biotic factors (e.g., interactions with natural enemies).
DOI of original article: http://dx.doi.org/10.1016/j.agrformet.2015.06.014. 0168-1923/$ – see front matter http://dx.doi.org/10.1016/j.agrformet.2016.01.064
2. In the absence of data on SBW densities, I am not sure how they can separate the effects of herbivory from the effects of weather on tree ring widths. It is standard practice in dendrochronology to remove the climate signal from the host tree ring time series using a non-host tree ring time series. However, it does not appear the authors measured tree ring growth in any non-host tree species. 3. Regarding the statistical analyses, the authors did not explain whether they accounted for temporal autocorrelation in their data when conducting significance tests (e.g., cross-correlations, Mann Kendall tests for trends). If they did not account for autocorrelation, the results are biased towards type-I error. Similarly, in at least one case (Figure 3), the authors conducted a large number of nonindependent hypothesis tests but they did not appear to correct for inflated type-I error resulting from these non-independent tests. 4. In general, the manuscript seems to overemphasize the role of climate in defoliator outbreaks. I am skeptical that climate alone can explain why an insect population might cycle (i.e., oscillate at a regular interval). This type of population behavior is widely thought to require delayed density dependence due to biotic influences (e.g., specialist natural enemies). 5. The overall clarity of the writing throughout the manuscript should be improved. Many sentences are difficult to understand. Anonymous