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Re: TT: shade tree diversity



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Marianna,

Your diversity quotient sounds a little low from what I remember
reading.  It is also way lower than it should be.  A significant disease
problem for maples, especially Norways, would wipe out your urban
forest.  Many cities have been learning about this problem as DED moves
across towns and cities.  Many were up to 80% American Elm, and over hte
last 25 years have lost 60 to 90% of those.  The discusions that I have
heard at conferences and read in journals seem to agree that no more
than 10% of trees should be one variety and 20% of any one genus.  Or
something like that.

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