windthrow

Stuart Brown stuart at zephyr.manawatu.planet.co.nz
Mon Apr 1 02:43:00 EST 1996


Terry Brown <tb at tbrown.lvlham.lincoln.ac.nz> writes:

>> >We did this ourselves as we have a VERY (underlined) windy site, so windy that
>> >almost nothing grows--we've tried gorse, radiata, corsican pine, flax,  This
>> >year we are trying broom, manuka, rugosa,
>[snip]
>> contorta and Pinus mugo may be worth looking at.
>
>Pinus 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.

Having a good planting method makes a difference. Also topping the trees 
prior to their 2nd winter helps. It's tough to do and we normally wait 
till they fall over. Then top, and a branch will become a new leader. 
Topping stops them swirling around in a circular manner.

Some people suggest not to release the trees after planting. This can 
help, it depends on the fertiliy of the site. Fertile sites have 
vigorous grass species which can smother the trees eg fog, ryegrass. Also 
these site can tend to lead to more top growth relative to root growth 
which can lead to incresed toppling.
Poorer fertility sites have less trouble with unsprayed grass smothering 
trees.

It has been suggested some releasing chemicals have different affects on 
tree root growth. Has anyone got information on this?

I've observed very high porina caterpiller infestations in soil during 
the early winter 9 months after releasing. This leads to substantial soil 
softening around the tree and toppling. I suspect some residual herbicides
can affect this problem - by providing an ideal environment for the 
porina.

Stuart Brown
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