Oral Submission Presentation by Blake Foster - New Zealand ...

~ Herbaceous cover. Wildings have difficulty establishing within a vigorous
herbaceous cover. This has been demonstrated over on Mt Cook station, where no
wildings can be found in the dense grass / clover cover which established quickly after a
fire destroyed a large area of a wilding Corsican pine forest. Where trees are felled, and
the resulting slash is not so thick as to prevent any light reaching the ground surface,
herbaceous growth, particularly of grasses, can be sufficiently vigorous to prevent wilding
re-establishment from seed for a number of years (see above). Evidence of this can be
seen at a number of sites on Pukaki Downs.
• Maintaining improved pasture and intensive grazing.
Pasture which is improved by seeding and fertilising will not be invaded by wildings. This
is well shown on the Canterbury plains, despite the presence of a wide range of spreadprone
conifers. There is also good evidence on Pukaki Downs, where the hay paddocks in
block 31 and parts of block 25 are free of wildings despite the fact that there are forests of
contorta pine adjacent. Although improved pasture will prevent wilding invasion, it is
acknowledged that much of Pukaki Downs does not lend itself to this form of wilding
prevention. Also, it must be remembered that a) this improvement and the grazing which
it can support must be maintained, and b) if the seed rain from immediately adjacent trees
is high, then even a relatively small easing of grazing and/or fertiliser regimes can result in
wildings getting established. In addition to improved pasture, the cropping of land for
arable purposes will deliver the same wilding prevention outcome.
• Planting a margin of less spread-prone trees.
The theory here is that in a forest, most cones are produced on edge trees which have
green crowns extending to ground level - as opposed to the smaller and higher canopies
of internal trees. In addition, edge trees are more likely to disseminate seed onto
unplanted adjacent land. Therefore, if the margin of a forest is planted with a zero or less
spread-prone species, the risk of wilding spread is reduced. If the marginal species is
faster growing than the forest species, then it can also create a greater physical barrier to
the spread of seed. However, this marginal planting can only be most effective on flat
land. Where the forest is on rolling or hilly land, especially if this faces into the prevailing
wind, then there are greater opportunities for seed to be picked up from the internal tree
canopy and the effectiveness of marginal planting is diminished.
Assisting containment on Pukaki Downs.
Taking the above points in mind, the best containment management options appear to be
the:
~ Establishment of forests of less spread-prone species, such as the radiata x
attenuata hybrid, on areas immediately to the west of the contorta forests most likely to
remain intact – such as on blocks 12, 13, 19 and the western parts of block 9. In a
continuation of this western edge planting to the north of the property, further
establishment could be made on the eastern slopes under the Little Rhoboro Hills (blocks
20 and 14) - and also along the northern boundary with Ferintosh, down to SH80. Over
time, the 20m strip of less spread-prone species could be extended down the northeastern
margin alongside SH80, thereby minimising the spread of wildings onto the
highway margin. Such a strip could be established wherever spread-prone trees are likely
to grow alongside SH80. As they would be on the western side of the road, there should
be no risk of promoting highway icing during the winter.
To the east of SH80 in block 32, improved pastures and grazing are restricting fringe
spread westwards from the lakeside forests of contorta pine – and also from smaller
planted areas of Corsican pine and Douglas-fir. Additional forests, or a 4-row strip, of less
spread-prone species could be established along the western margin of these more
spread-prone species, in order to further reduce the risk of unwanted spread.
~ Maintenance of improved pasture and associated grazing (or arable cropping)
where it is currently restricting wilding establishment. This is in blocks 31 (especially
around the Dusky Reserve) and 32 and further to the west in the southern half of block 25,
just beyond the forested blocks 9 and 12. The hilly topography, limited moisture
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