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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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