date: Wed, 07 Aug 2002 09:24:31 -0500 from: David Stahle subject: Holocene reviews to: k.briffa@uea.ac.uk Dear Keith: Hope you are well and that I get to see you again soon. Sorry for the delay on these reviews, but finally I have an opinion. The Speer et al. paper is weak and unsuited for publication. The Hunzicker and Camill paper is more problematic. Pretty strong analyses, but the calibration and verification are awful, and I'm afraid that can probably be traced back to the half ass chronology development procedures. I wouldn't publish that one either, unless they go all the way back and fix the chronology development, and then substantially improve the calibration and verification. The reviews are attached and reproduced below. Sincerely, Dave Review of J.H. Speer et al.: "Assessing the dendrochronological potential of Pinus occidentalis Swartz in the cordillera Central of the Dominican Republic" submitted to the Holocene. This is an esoteric and highly speculative paper on annual ring formation in West Indian pine, that draws conclusions only marginally supported by the analysis. The evidence for annual rings and "crossdating" is weak. They only report the "average interseries correlation" in Table 3, which was just 0.44, and it is not entirely clear how they arrive at this number (18 radii are mentioned on p. 12, ten trees are listed in Table 3). They do not show a plot with all ring width time series to allow readers to judge for themsleves. They also cite a "statistically significant correlation" of only 0.34 with annual precipitation at Jarabacoa as evidence that the chronology does produce annual rings. This is a very weak relationship, and alone hardly sufficient to prove the annual nature of the growth rings. They do not display a time series comparison between the tree-ring and climate data to allow the reader to judge. The other three study sites did not crossdate and did not relate to climate. So the evidence for annual rings and a useful climate record is hardly sufficient to state (as they do in the abstract) that: "P. occidentalis may allow dendrochronological reconstruction of climate, fire history, and other environmental processes that operate on the island of Hispanola." The paper is heavily weighted toward a disription of ring types and ring quality, and six of the nine figures are photos of rings. The paper might be better suited for a journal of wood anatomy. Review of David Hunzicker and Phil Camill: "Using a new 672-year tree-ring drought reconstruction from westcentral MontanaŠ" submitted to the Holocene. This is a well written, well executed paper that I would unfortunately not recommend for publication in the Holocene. It's a shame to read a paper like this. It is very well informed, well referenced, places the work in a good scientific context, and includes strong statistical analyses. However, the attention paid to the analyses and interpretation of the reconstruction was evidently not paid so carefully to the fundamental tree-ring chronology development. They call it "crossdating," but the best I can tell from the limited discussion it was simply computerized correlation matching of measured time series, with a massive culling of the data to pare down to those time series that produced straightforward correlations in a COFECHA analysis. I was astounded to read that their final chronology used only 61 out of the 152 trees sampled for the study. The 60% of the trees not included apparently suffered from "complacency, unresolvable sections of missing rings, or low interseries correlation values." This appears to be the first penalty for not applying rigorous dendrochronological methods to the chronology development. I find it incredible that over half of the Ponderosa pine samples would not be useful. I can't help but suspect that by relying on COFECHA output, without any hard-nosed microscope work and rigorous crossdating with the wood samples themselves, you at best default to the simple, straightforward trees without missing rings. That is, you default to a less climatically sensitive subset of trees. This appears to be the second penalty for the seemingly inexpert, quick and dirty chronology development. These authors have obviously worked hard on this study and bring excellent analytical skills and knowledge of the literature. The paper itself is exceptionally well written (with a minor complaint concerning the over use, and at times incorrect use of the term "teleconnection"). But the calibration and validation reported in the paper are clearly awful, and that surely ought not be the case for Ponderosa pine on moisture-stressed sites in Montana. One hates to be non-supportive of their work, so much of which is high quality, but it seems to come down to fundamentals, and here the fundamental dendrochronology and chronology development are in question. And I also do not think it advisable to publish a reconstruction that explains maybe 21% of the variance in the instrumental climate data, when using an arid site conifer as the predictor (the persistence in the standard chronology may be inflating even that figure). I just can't believe the calibration could be so weak. It seems they need to revisit their chronology development work, and dig deeper into the climate response of their chronology. Then look very carefully at climate data itself. These climate data are not guaranteed to be homogeneous, especially in the mountain West during the early 20th century. If all this could be done, and if the variance explained in both the calibration and verification periods could be improved, then publication in the Holocene would be well justified. Attachment Converted: "c:\eudora\attach\Speer_Holocene8.02.doc" Attachment Converted: "c:\eudora\attach\Hunzicker_Camill8.02.doc" -- David W. Stahle Professor Dept. of Geosciences Ozark Hall 113 University of Arkansas Fayetteville, AR 72701 USA 479-575-3703 479-575-3469 (FAX) dstahle@uark.edu http://www.uark.edu/dendro http://www.uark.edu/xtimber