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Value of truffle-inoculated trees

dwheeler at teleport.com dwheeler at teleport.com
Thu Aug 20 08:35:25 EST 1998

In article <6rdta9$hjs$1 at nnrp1.dejanews.com>,
  kyosai at yin.or.jp wrote:
> This is a technical question Dan (by the way,what`s up?),after clear cutting,
> wouldn`t the fungi remain in the soil? Seeking a new host, such as the
> infamous Scleroderma, by traveling with the ground water downslope? With the
> number of mycorrhizal fungi that are known in the Pacific Northwest, would
> not the shear number and diversification insure re-inoculation of seedlings
> or shrubs that were replanted on clear cut lands? Let me know.
Good question. While Scleroderma can and does form mycorrhizae with many host
trees and shrubs, it is not commonly associated with Douglas fir that is known
(although I _have_ found S. hypogaeum with Douglas fir).

Most mycorrhizal fungi die within a year of clearcutting. This is even more
pronounced when the area is denuded of all plant life, such as in heavy slash
fires, which until recently were common.

It now appears that there is a succession of mycorrhizal fungi as trees and
shrubs mature and a forest develops. For example, while Endogone can be
associated with very young seedling Douglas fir, Cantharellus formosus and
Tricholoma magnivelare are seldom, if ever associated with seedling fir.

Close monitoring of one nearly monoculture stand of Douglas fir in Clackamas
County over the past 13 years strongly suggests Tuber species are unusual in
very young trees, even though I have found a Tuber gibbosum with a seedling
Douglas fir less than 8 inches tall and probably less than 3 years old.

Since mycorrhizal fungi are generally ignored in modern forestry,
recolonization is haphazard and spotty.

Fortunately, the most common animals found in clearcuts also are instrumental
in re-introducing many hypogeous mycorrhizal fungi via feces. But unless
these animals are encouraged rather than discouraged, future tree health is
in jeopardy.

There are a host of different things that affect mycorrhizal fungi
development, including soil type, soil pH, slope, water availability,
available hosts, degree of rock and type of rock; native animal species,
large woody debris left as cover for animals and the dispersal of said
debris; elevation, etc.

Most of these have not been covered. And in general, the mycorrhizal fungi
have been so infrequently cultivated as to be of no real consequence. For
example, no one knows how important Thelophora terrestris is is seedling tree
survival, nor how fast that mycorrhizal fungi allows trees to develop, and
under what conditions. While Pisolithus tinctorius is commonly introduced to
seedlings in nurseries, that fungus is an indication of _very_ poor growing
conditions in nature. What role these fungi, often not even native to
clearcuts, affects regeneration has not been documented. Nor is it likely to
be in the near future.

Daniel B. Wheeler

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