Hi -
I suggest you look into the work of Ray Calloway, prof. at U Montana. He's
done some fascinating work along these lines.
Cheers,
Michael Cooperman
-----Original Message-----
From: Ecological Society of America: grants, jobs, news
[mailto:[email protected]] On Behalf Of Martin Meiss
Sent: Wednesday, April 13, 2011 9:19 AM
To: [email protected]
Subject: Re: [ECOLOG-L] Rhetorical question on trees
It's probably more reasonable to think of the soil-building
properties of leaves (and other things that fall out of trees, like twigs,
fruit, bird poop, etc.) at the level of the forest rather than at the level
of the individual tree. After all, leaves don't fall straight down, and
after they hit the ground, they don't necessarily stay where they fall
(wind, you know). Even if they did, there is no guarantee that each branch
of a tree has a root waiting under it. Additionally, understory plants
growing beneath the tree compete with the tree for water and nutrients,
since their roots occupy the same soil. Thus, in a situation where water
limits growth, a tree, by enriching the soil below its crown, could hurt
itself by favoring the growth of small plants that compete with it for
water.
If a tree is to benefit nutritionally from loss of leaves, etc.,
probably the best thing is to minimize the lose by pulling as much nutrient
as possible from the parts to be shed. This is what's going on when leaves
turn color before falling off in autumn of the temperate zone. However,
plants have never evolved a way (to the best of my knowledge) of
remobilizing cellulose, hemicellulose, or lignin, so these materials can't
by scavenged metabolically. However, they are also materials not containing
much of nutritional value; their loss is primarily an energy loss.
The benefit of withdrawing nutrients from leaves leads to selective
pressure for proper timing of the withdrawal. If trees do it too early,
they loose part of the growing season, and if they do it to late, frost can
kill the leaves before the nutrient is withdrawn (and dead leaves no longer
have the metabolic machinery needed to support withdrawal of nutrients). In
my yard I have an introduced species of mulberry, far from the climate where
its ancestors evolved, and in the fall it seldom reads the climatic cues
(day length and temperature) correctly. Its leaves stay bright green till a
hard frost kills them, then they fall to the ground, sometimes in a single
night, still bright green. Surprisingly, the tree still grows like hell,
and every few years I have to trim a lot of wood out of it.
Martin M. Meiss
2011/4/13 Martin Koechy <[email protected]>
> Hi Geoff,
>
> You are right, that's what trees tend to do, but the intensity is variable.
> The keyword is "island of fertility" if you look for more information and a
> classical paper on this subject is Zinke PJ (1962) The pattern of influence
> of individual forest trees on soil properties. Ecology 43: 130-133.
>
> Cheers,
>
> Martin
>
> Am 2011-04-13 um 04:59 schrieb Geoffrey Patton:
>
> > ? To what degree do trees self-fertilize by dropping leaves and building
> their own humus ? They capture energy from the sun and nutrients from the
> air (and soil) and some of that production feeds the soil upon which the
> following year's growth depends. The soil biota processes the wastes,
> further captures atmospherically-deposited nutrients, and makes it all newly
> available for further growth, I would imagine. Apologies for being a marine
> biologist but this seems like something that might have been researched
> already. Yes or no?
> >
> >
> >
> > Cordially yours,
> >
> > Geoff Patton, Ph.D.
> > 2208 Parker Ave., Wheaton, MD 20902 301.221.9536
>
> ------------------| http://sci.martinkoechy.de |--------------------
> Dr. Martin Köchy (Koechy)
>
> Johann Heinrich von Thünen-Institut
> -Bundesforschungsinstitut für Ländliche Räume, Wald und Fischerei-
> Institut für Agrarrelevante Klimaforschung
>
> Johann Heinrich von Thuenen Institute
> -Federal Research Institute for Rural Areas, Forestry and Fisheries-
> Institute of Agricultural Climate Research
>
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