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TT: Re: RE: Fall color peaking in Baltimore

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> From: RTEllsberry <rtells@Flora.Com>
> To: Community_Forestry <TreeTown@Majordomo.Flora.Com>
> Subject: TT: RE: Fall color peaking in Baltimore
> Date: Tuesday, November 18, 1997 1:49 AM
> Fall color in Athens, Ga.(NE GA) is excellent still. The
sourwoods(Oxydendrum
arboreum) are brilliant as usual. Blackgums are also outstanding too . 
Is it not a decrease in "chlorophyll a" that triggers the showing of other
chlorophylls
and anthocynins and thus the fall color occurs (due to reduced photoperiod)
?
Fall color in piedmont region of Ga.has been excellent. 
Craig
>  -----------------------------------------------------------------------
>  On Tue, 4 Nov 1997, Thomas W. Kimmerer wrote:
> 
> > ... The temperatures of this fall would tend to delay peak coloration.
> > The onset of autumn, the withdrawal of nutrients from the leaves into
> > the tree, is set by daylength, not by temperature (many ornamentals
have
> > odd coloration timing if they come from other latitudes).  However, the
> > duration of leaf color change, and the interval between onset of autumn
> > and leaf drop is a function of temperature, particularly of minimum
> > night temperatures.  That's why cold, clear nights give us the most
> > intense colors, and why New England has a "brighter" autumn than the
> > South ...
> 
>  -----------------------------------------------------------------------
>  I'm probably not the only one in TreeTown who thinks often about
>  Tom Kimmerer's evocative commentaries on tree physiology.  Gary, I
>  and other listees are (returning) students at Towson U., north of
>  Baltimore, where we enjoy an astonishing 'academic forest' of
>  well-cared-for and old-growth trees -- not being a true 'arboretum'
>  campus (which could be the subject of another great thread :) ...
> 
>  OK, I'll break here for a moment.  Towson U. has awesome Sycamores,
>  American Beeches, (Yellow) Tulip Poplars, mixed native Oaks & Maples
>  which have, for a hundred years, had buildings and roads landscaped
>  around them ! Plus a variety of 'introduced' ornamentals, particularly
>  Japanese Red Maple (many colorful cultivars), European Beech, Japanese
>  Zelkova, and one prominent, maturing specimen in the middle of campus
>  which I think is a Bald-Cypress, but which Gary might correct me on.
>  The Towson squirrels are more conspicuous than the birds, and much
>  more numerous than the school mascot, which happens to be the tiger ...
> 
>  A walking tour of Towson U. is highly recommended, lacking perhaps
>  in American Elms :( ... I've heard that there are also lots of Pecans,
>  and I don't know if they are native or not, at least this far north.
>  I haven't noticed many Magnolias.  Purple Norway Maples are also common.
>  The forestry crews seem to keep the Ailanthus out pretty well (or is
>  that a function of such broad diversity?)
> 
>  Apologies for making this so long.  Looking at the remaining leaves
>  this time of year, it's obvious that bright sun hitting them ac-
>  celerates (amplifies) their coloration.  Somehow the trees have a
>  'memory' of the current climatic conditions (to borrow a computer
>  term).  So what I'm wondering is, where are these 'memories' recorded?
>  My naive guess is in the leaves themselves, that the biology of one
>  single leaf triggers when it changes color and drops, independent of
>  its peers.  Otherwise the entire tree, or at least large sections
>  of it, would 'fall' all at the same time, which does not appear to
>  be the case (for most resident deciduous species).
> 
>  Thanks for letting me go off so.  It's a beautiful autumn :) ...
> 
>  Richard@Flora.Com
> 
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