date: Wed, 07 Aug 2002 09:24:31 -0500
from: David Stahle <dstahle@uark.edu>
subject: Holocene reviews
to: k.briffa@uea.ac.uk

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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 Montana" 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.

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Attachment Converted: "c:\eudora\attach\Speer_Holocene8.02.doc"

Attachment Converted: "c:\eudora\attach\Hunzicker_Camill8.02.doc"
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-- 
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

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