[VIPS] Ideotype question (fwd)

'Toby' H D Bradshaw toby at u.washington.edu
Thu Oct 12 13:48:06 EST 1995


Forwarded from Tom Hinckley, University of Washington

-Toby Bradshaw
toby at u.washington.edu

---------- Forwarded message ----------
Date: Thu, 5 Oct 1995 16:13:36 -0700 (PDT)
From: T. Hinckley <hinckley at u.washington.edu>
Subject: Re: Ideotypes with/without crown

I agree LAI is important and is much greater in PNW than other 
regions.  

However, much of this discussion gets back to points originally raised by 
Jerry Leverenz (Leverenz and Jarvis 1979. J. of appl. Ecol., Leverenz and 
Hinckley. 1990. Tree Physiology) where Jerrry suggest that there were two 
key attributes of a productive tree.  The ability to produce foliage and 
the ability to have foliage, once produced, function in low light 
environments.  A stand with a LAI of 6 adsorbs approximately 95% of the 
incoming radiation whereas a stand with a LAI of 12 adsorbs (absorbs) 
approximately 99+%.  The second stand, with an additional 4% light 
adsorption, may be twice as productive. Extinction coefficients, leaf 
angles and ability to function at low light levels will all be important.

Tom

On Thu, 5 Oct 1995, Don.Dickmann wrote:

> The point about foliage efficiency is well taken, but even in densely spaced
> plantations LAI is very important.  For example, my casual observations
> comparing poplar plantations in the Pacific NW vs. those in the Lakes States
> and Northeast US indicate that the NW plantations carry far higher LAIs.  The
> differences in light levels, weed competition, etc. in our plantations vs.
> yours in the NW is striking; even in bright sun it's very dark under the NW
> plantations. I'm convinced that this high LAI is a major contributor to the
> high productivity of NW plantations.  Certainly we're talking different
> clones, for the most part, but my understanding is that on the east side some
> of the same clones that we plant back here have been used, but their canopies
> sure do look different.  The why questions associated with these observations
> (if they in fact are true) would make for some interesting research.
> 
> Don
> 





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