windthrow

[Terry Brown]

Stuart Brown wrote:
> 
> Terry Brown <tb at tbrown.lvlham.lincoln.ac.nz> writes:
> >contorta is a class B noxious weed (in New Zealand), (is that
> >only in some regions perhaps), anyway, it's very hard to control the
> >spread, particularly in windy sites.  A 20 year programme at
> >Ruapaehu has largely brought the problem under control there, but I
> >know there are diverse tussock ecosystems in the Canterbury /
> >Arthur's Pass area being quite rapidly destroyed by P. contorta
> >spreading from old Forestry Dept. trials.  Initial control is very
> >expensive.
> 
> P. contorta spread would only be a problem if one is ajoining an ungrazed
> area. I don't think that's the case here. I'm also considering P. contorta
> for an equally exposed shelter belt.

That's probably true to a degree, although there seems to be some
debate about how far it will spread in the wind, opposite sides of
the fence in the Ruapaehu case claiming something like 30 m and 
25 km, or some similarly ridiculous dichotomy.  I've seen solitary
seedlings appear 500 m up hill of the nearest mature trees around
Arthur's Pass.  Given the small seeds I would imagine it could travel
much further.  And as it can start seeding at I think about 3-4 years
there's plenty of potential for a rapid stepping stone effect.

Cheers -tb

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Terry Brown                      email: brown at lvlham.lincoln.ac.nz
Lincoln Environmental            http://tbrown.lvlham.lincoln.ac.nz/~tb
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