Fwd: Grist | Global Citizen 07.12.99, Excellent article on Trees

Wed Aug 18 01:25:54 PDT 1999

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> GLOBAL CITIZEN 
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> The Forest Is More than a Collection of Trees 
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> A weekly rumination on sustainable living
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> <citizen070699.htm>Rewriting the Story of the Ant and the Grasshopper
> 07.06.99 
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> <citizen062899.htm>Ethnic Cleansing in the Chicken Coop
> 06.28.99 
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> <citizen062199.htm>Climate Scientist Takes His Computer Model Seriously
> 06.21.99 
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> <citizen061499.htm>Clustering -- Good Idea, Hard to Do
> 06.14.99 
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> <citizen060799.htm>There's Farming and Then There's Farming
> 06.07.99 by Donella H. Meadows 
> 07.12.99 
>
> About 40 years ago, a young Dartmouth biology professor named Herb Bormann
> took a tomato plant, gently pulled its roots apart into two bunches, and
> planted it in two pots, one clump of roots in each pot. He watered both pots
> until the plant got established. Then he watered only one pot. The tomato
did
> fine.
>
> Photo: David Parsons, NREL/PIX
>
> Then he repeated the experiment many times with the addition of a second
> plant rooted only in the unwatered pot. Some of those second plants also did
> fine. Others wilted, but more slowly than did control plants in unwatered
> pots without a "donor." Later experiments showed that one plant could pass
> not only water but also radioisotopes to another.
>
> Bormann began digging around in a white pine forest near the Dartmouth
campus
> and injecting tree roots with dyes, herbicides, and radioactive tracers. He
> found that the trees not only passed these markers around, but that their
> roots had actually grown together into complex networks of "grafts." Through
> the grafts, large trees tended to pass nutrients to smaller, weaker trees.
> They even kept alive stumps, which went on growing, sometimes for decades,
> though they never regenerated branches or leaves.
>
> Bormann later wrote: "This research indicated that the role of ...
> competition in determining which trees in a ... stand will survive was
> overrated. In many stands, many trees are linked into organic unions. ...
> Participants in the union have lost at least part of their individuality and
> are subject to the ... influence of their grafted companions."
>
> Even when Bormann did this research, the knowledge that trees interconnect
> below ground was not new. One of his teachers had told him how oak trees
> transmit diseases through root grafts. As long ago as the 1920s, root grafts
> had been observed in white pine, Douglas fir, and balsam fir forests, as had
> the phenomenon of "living stumps."
>
> By 1966, Bormann and his colleague B.F. Graham could write a review article
> listing more than 180 scientific articles on the passage of materials
between
> the roots of at least 150 species of trees, including oak, maple, linden,
> spruce, ash, larch, birch, fir, and pine. There are root grafts between
> different species -- maple and birch, birch and elm, and sandalwood and the
> tropical tree Eugenia. (The grafts reportedly give the Eugenia the scent of
> sandalwood.)
>
> Sometimes the transfers occur through root grafts. Sometimes they just pass
> through the soil, as with Bormann's tomatoes. Sometimes there are inter-tree
> carriers, mats of cooperating fungi called mycorrhizae (pronounced
> mike-o-rye-zee), which intermingle with tree roots, subsist on sugars
> produced by the tree leaves, and in return mobilize nutrients from the soil.
> The most common traffic is in sugars, growth hormones, herbicides, and
> disease organisms. Less common are transfers of water (in large amounts) or
> mineral nutrients.
>
> This underground tree trade is apparently well known to biologists, but they
> haven't made a big deal of it. I have taken many biology courses, but I was
> surprised when forest ecologist Scot Zens mentioned root grafts in a
> conversation a few months ago, as if I knew about them. I didn't. The very
> idea stopped me in my tracks. It changed my whole view of what a forest is.
> What? The roots grow together? The trees pass stuff around? What does that
> mean?
>
> What does it mean to forest management, to selective harvesting, to
> clear-cutting? What does it mean when acid rain falls, when drought comes,
> when herbicide is sprayed, when we try to fight off tree diseases? What does
> it mean to our cultural notion that the world runs on competition, not
> cooperation? Are we biased toward seeing only collections of individuals
> rather than interconnected systems? Have we literally been failing to see
the
> forest for the trees?
>
> The scientists who blazed research trails on tree transfers, instead of
> following the well-trampled professional highway investigating competition,
> have written mainly about what root grafts mean for forestry. Cutting a tree
> but leaving its stump may be no help in preventing the spread of disease.
> Trying to kill selected trees by injecting herbicide could spread the poison
> to non-targeted trees. Girdling trees with strong root grafts may not kill
> them, at least not below the girdle. Interlocked trees are probably more
> resistant to wind throw but less resistant to disease. Selective cutting may
> produce unexpected results -- you may remove not a competitor but a partner.
>
> I would love to draw deeper lessons than those practical ones. I have a bias
> opposite to the one my science professors so assiduously tried to instill in
> me. I prefer to believe in cooperation as a working principle, not
> competition. I like to think about complex interacting systems. I have an
> instinctive (some would say irrational) notion that the forest knows and
> weeps when a single tree falls. I love the notion of secret traffic among
> trees.
>
> Like my scientific brethren and sistren on the opposite side of the bias, I
> am not blind to the social implications of lessons purportedly drawn from
> nature. Aha! I can say. Big trees support small trees. Trees stand together,
> they don't struggle against each other. When we take one away, we send waves
> through an interconnected community. If this is true for trees, might it not
> work for people?
>
> Which is, of course, as oversimplified a picture as is the notion that the
> forest is nothing but the sum of its trees. There is plenty of
competition in
> a forest. Inter-tree networks spread disease and poisons as well as
nutrients
> and hormones. No one understands the reason -- if there is one -- why any
> tree shares anything with another. Nature is too complex to ratify our
simple
> worldviews. Whatever we understand about the interconnections among trees,
> there is probably much more that we don't understand.
>
> If there's any unbiased lesson to be drawn from the community of trees,
> that's probably it.
>
>
> - - - - - - - - - 
>
> Donella H. Meadows is director of the Sustainability Institute and an
adjunct
> professor of environmental studies at Dartmouth College. 
>
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