Redwoods in Nature    Michael Davie
   Apr 26, 2004 18:26 PDT 
Hello all-
I was wondering if anyone read the new article in Nature about redwood height maximums. I don't get the journal, so I could only read the online general consumption article, which was very interesting. It predicted the physical height ceiling of a redwood at around 420 feet before it would become theoretically unable to support any more growth due to water deficits. I was wondering what model of tree hydraulics they were basing this on? I don't even know if all of the mechanisms of water transport have been decisively figured out yet, I thought it was still debatable and not fully understood, but I may not be operating off of the most recent information available. Hell, the information I have I only barely understand. BVP, if you're reading this, maybe you could shed some light? Anyone?
Re: Redwoods in Nature
   Apr 28, 2004 06:51 PDT 

Yes, I work closely with both George and Steve in redwood research. The paper comes at the limits to tree height from a physiological perspective. The beauty of the work is that four, completely independant methods were used to estimate a potential limit to redwood tree height at Rockefeller Forest - the world's tallest forest.

Delta 13 concentrations in foliage, size/mass ratios of foliage, photosynthetic density per mass of foliage, and predawn and midday moisture stress levels were all used to predict a maximum possible height. All four methods resulted in values between 122 and 130 m.

A tree will almost certainly encounter some difficulty before achieving this. The tallest tree currently has had at least six episodes of dieback and regrowth.

Keep in mind this is a potential maximum for one site during one climatic period. Also, this research does not address any potential genetic limitation to growth.

I hope this helps...
RE: Redwoods in Nature    Robert Leverett
   Apr 28, 2004 09:34 PDT 


How much is known about the rates of growth for different West Coast
conifers? How does Douglas fir compare to redwood for the first 100
years? The first 250, 500, 1000? I'm presently stuck on trying to better
understanding growth rates, relative and absolute, for white pine. We're
seeing high absolute volume growth in the Mohawk pines that are in the
100 to 150-year age class, which I think surprises some of our forester
friends. What is this period of growth like for the West Coast conifers?
Given their great longevity, has anyone plotted graphs of volume
accumulation over a 1,000 years or more?

For those trees that get repeatedly pruned back, is there any
evidence that they return to their previous heights at faster or slower
rates than that which originally got then to a particular height?

On a slightly different theme, silviculturists often develop fixed
notions of growth rates for species over time. In addition, the wood
producers in southern New England see diameter changes much more readily
than they see height changes when trees are in the 80-foot and above
height class. I have often observed that a 130-foot white pine in Mohawk
looks basically the same to them as a 155-footer. They just don't see
that extra 25 feet. However, they would all readily see a 25-foot
difference at the 50 to 75-foot levels.

   I'm inclined to wonder if the difference in visual impact of an
additional 25 feet of height acquired at an early stage of life for
white pines as opposed to the addition achieved at a much later stage
shapes one's perceptions about how fast the trees are growing. The new
growth obviously look shorter at greater distances to all of us, so one
has to learn to compensate. Our buddy Will Blozan is one of the best
I've seen at doing that for eastern trees. I can do it too, but I
require a longer period of site eye calibration than Will does.

   I realize that I'm straying into uncharted territory here, but I'm
trying to understand the differences in perception about the growth that
some of us see in the eastern white pines versus that perceived by the
vast majority of the wood producers who visit pine stands with us. Of
course, Ents have the benefit of constant reinforcement from repeated
measurements, but assessing growth is the business of wood producers. I
would have thought that the majority would be able to accurately assess
height, diameter, and total volume for young and old pines alike. I'm
not judging their talents at sizing up the number of logs in the lower
trunk. All do that well, but their talents don't extend to the whole
tree. How do you find the estimating eye of wood producers to be out
there on the West Coast for the whole tree estimation?