Comments on: Wilson, Pisaric and Gaspé

By: New Light on the Lost Cedars of Gaspé « Climate Audit

New Light on the Lost Cedars of Gaspé « Climate Audit — Tue, 07 Jun 2011 01:28:17 +0000

[...] A data set that was almost as controversial in MBH98 as the Graybill bristlecones was the Gaspé cedar chronology used by Jacoby and d’Arrigo. An interesting new cedar chronology from Quebec has just appeared at NCDC, shown below. The third chronology shown below is an unreported update to the Gaspé series. I reported the unreported update in a 2005 post (see comments by Martin Wilmking, a young dendro interested in the divergence issue). Also see 2007 discussion here. [...]

By: DeWitt Payne

DeWitt Payne — Sat, 31 Mar 2007 07:15:40 +0000

Re: #56

All other things being equal, what happens to the relative partial pressures of CO2 and water with altitude ?

Assuming that CO2 is well-mixed, which I believe is the normal situation outside urban areas and other local sources, the ratio of partial pressure of CO2 to total pressure should remain constant. Water vapor pressure, OTOH, decreases faster than that because the vapor pressure of water is also determined by temperature and temperature decreases with altitude. In other words, water vapor condenses to the liquid (or the solid if it’s cold enough), with clouds being a classic example. So the ratio of CO2 to water vapor should increase with altitude.

By: Doug Fox

Doug Fox — Thu, 29 Mar 2007 16:00:37 +0000

“If I could ask a dendrochronologist” part III:

Transverse sections of xylem generally reveal at least three zones: 1) active transport and storage of water and carbohydrates, 2) inactive water transport (plugged vessels or tracheids) but active carbohydrate storage, 3) heartwood (in heartwood forming trees), 4) either instead of or around heartwood, an inactive, dry, low nitrogen, protection wood formed in response to death of several lower branches. Within the first zone, at least, there is a moisture gradient with the latest ring containing the highest m.c.

Particularly in regard to moisture content, does this affect dendrochronology and how so? (Would recent growth be inflated due to high moisture content?)

By: Steve McIntyre

Steve McIntyre — Wed, 28 Mar 2007 14:15:46 +0000

#63. You’ll have to ask TCO who has returned today after a year’s absence. Hi, TCO.

By: Doug Fox

Doug Fox — Wed, 28 Mar 2007 14:11:26 +0000

Another “if I could ask a dendrochronologist…” question:

Trees grow most rapidly at the base of the live crown. The base moves higher over time due branch death generally attibuted to loss of hydraulic capacity on long old limbs and/or to a reduced photosynthesis to dynamic mass ratio (living tissue on large limbs is too great for the amount of light captured on shaded leaves and storm-damaged leave-bearing twigs).

Fritts (1976)indicates that the first sentence is understood, but is this taken into account on these studies? I have dated branch death on some trees but I haven’t tried cedar yet. (It is much easier on dissected trees than with cores.)

Is there a 12-step group for those of us who are not retired and need to spend more time away from this site?

By: Don Keiller

Don Keiller — Wed, 28 Mar 2007 09:48:09 +0000

re 56, you are right stomates open up at low [CO2]- and in doing so decrease the leaf’s water use efficiency as the water diffusion pathway is the same for CO2.
The ultimate limiting factor, however, is not a stomatal limitation, but that of substrate availability- (in this case [CO2]) at the active site of RUBP carboxlyase.

By: Don Keiller

Don Keiller — Wed, 28 Mar 2007 09:39:57 +0000

re #58, yes I am aware of this. But it is all based on correlations. Correlations do not prove cause and effect.
Im any case there is an increasing descrepency between tree ring width and “temperature” over the latter half of the 20th century, so the correlation breaks down.
CO2 is undoubtedly a significant confounding factor -(eg Telewski et al (1999). Wood properties and ring width responses to long-term atmospheric CO2 enrichment in field-grown loblolly pine (Pinus taeda L.). Plant, Cell and Environment 22: 213-219.
The fact of the matter is there is not enough experimental data available to underpin and justify the assumptions that are being made about the relationship of tree rings and temperature.

By: Steve McIntyre

Steve McIntyre — Wed, 28 Mar 2007 01:36:15 +0000

#59. I’m in. Didn’t you get my email?

By: bender

bender — Wed, 28 Mar 2007 01:24:43 +0000

Re #47.
#46 was serious. Therefore your offer of employment is accepted. Now we need to hear from the white hat, Mr M.

By: Bob Weber

Bob Weber — Wed, 28 Mar 2007 01:06:54 +0000

#53. You might take a look at these 2 references. K. Briffa brief at aric's Global Climate Change Student Guide Bob