Comments on: Rob Wilson on Bristlecones

By: Mark T

Mark T — Fri, 13 Nov 2009 06:08:31 +0000

The relationships could be even more complicated than that.

Mark

By: bender

bender — Fri, 13 Nov 2009 02:37:06 +0000

To highlight the most relevant bit:

If growth, temp, precip, CO2 interact in the following way, with all effects & synergistic interactions positive:

G = T + P + C + T*P + T*C + P*C + T*P*C

then what would happen if your reconstruction model was mis-specified as:

G = T + P

Ans: If the 20th c. were a bit warmer, a bit wetter, a bit richer in CO2, a bit more whatever, then your reconstructions would be a lot more than a bit hockey-stick shaped. Why? You’ve incorrectly attributed the multiplicative synergy to independent additive effects through a model mis-specification.

I wonder if Dr. Wilson would care to comment?

By: bender

bender — Fri, 13 Nov 2009 02:33:34 +0000

Re: bender (#33),
Bump.
People are speculating now about CO2 fertilization of Yamal larch. I want to highlight that this has been discussed already, years ago, in the context of a fuller model of bristlecone pine growth – a model that includes not just precipitation, but also interactions between terms – especially temperature * precipitation.

By: SteveSadlov

SteveSadlov — Mon, 26 Nov 2007 19:26:46 +0000

In the case of the BCPs in the Whites, out. Ain’t no porcupines in that area.

By: bender

bender — Mon, 26 Nov 2007 18:08:56 +0000

Re #37
Scarring due to porcupines: in or out?

By: bender

bender — Mon, 26 Nov 2007 18:06:19 +0000

Calling Dr. Wilson: #33.
If bcp growth is a synergistic function of P, T (i.e. drought-limited) then how do you reconstruct T, using S&K’s (2005) method of assuming high-elev bcps are T-limited and low-elev bcps are P-limited?

Steve: Shouldn’t it be proven that high-elev BCPs are T-limited? The California BCPs only go to an altitude that is measurably lower than the Colorado treeline at equivalent latitude. I suspect that precip still affects upper treeline.

By: Steve Sadlov

Steve Sadlov — Fri, 06 Apr 2007 15:55:46 +0000

IIRC the 20th century was pretty moist, as centuries, go, throughout the SW US, including the areas BCPs live in.

By: bender

bender — Fri, 06 Apr 2007 13:48:00 +0000

Bump. Echoing #39. Your presence is still requested Dr Wilson.
(Funny how JMS dropped out at after #35.)

By: Carl Smith

Carl Smith — Sat, 14 Oct 2006 17:30:04 +0000

As someone that spent many years growing plants and trees, it seems to me that all these sheep eating the undergrowth and leaving millions of little nitrogen laden balls of fertilizer in their wake are quite likely to have a pronounced positive impact on the growth rate of any trees they have been grazing under.

Anyone that has done organic farming could tell you that poop of any kind is one of the best accelerators of tree growth there is.

If this was happening a bit before and/or during the calibration period the temperature/soil-moisture signal will be well and truly magnified by the fertilizer signal, making growth ring comparisons to earlier times when sheep were not crapping under the trees a total nonsense.

By: TCO

TCO — Sat, 14 Oct 2006 16:14:14 +0000

Rob…some unfinished business in here.