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

most depleted existing cover and it has very low grazing pressure
(mostly none) – plus there is good scattering of young wildings just
approaching the age of serious coning.
• Phases of spread. Even though wilding numbers will increase in an
unmanaged situation, there is likely to be a ‘lull’ in the invasion rate
during the next few years. This is due to many of the coning outlier
trees (which arrived in the early 1990s and gave rise to the present
islands of fringe spread) having been removed, and their progeny still
having a few years to reach the age of significant coning. In addition,
the occurrence of ‘outlier’ invasions (from distant seed sources) is not
frequent, so it may well be some years before there are new wildings
appearing from that source.
The dominant spreading species will remain contorta pine, but there is likely to be an
increase in the numbers of Douglas-fir. The spreading vigour of this species has
increased significantly over the last couple of decades, probably due to the more
widespread occurrence of the symbiotic mycorrhizas which are so important for early
seedling survival and growth. In addition, it has a light seed which is borne in cones which
hang from the ends of branches, well displayed for the dispersal of seed by passing
winds. At present there are many mature Douglas-fir trees between SH80 and the lake,
and those already on Pukaki Downs are into their early years of seed production.
Priority control areas for minimising spread risk beyond present
locations (particularly off-station)
Boundary risks
Looking at the north, east, south and western boundaries of Pukaki Downs, the risk of
spread off-station varies from virtually zero to high.
• Northern boundary. This boundary is a long and irregular one,
stretching over 8 kilometers and bounding with Ferintosh station to the
east and DOC to the west. With the strongest prevailing winds coming
from the north down either side of the Rhoboro Range, the risk of seed
dissemination in that direction is generally low. This is supported by
fringe spread around older trees in the area all being to the south.
Having stated as much, the boundary does run from north-east to
south-west, and the spread event of the early 1990s (see above) has
shown that seed can be disseminated to the west – although
infrequently. In addition, there are coning contorta pine high up (to
900m asl) on the Rhoboro Range slopes in the northern most corner
of Pukaki Downs (block 30) which could quite easily throw seed to the
south-east over the Range onto DOC land in the upper Twizel river
catchment - where the low vegetation cover and zero grazing pressure
allows for ready wilding establishment. The middle third of this
northern boundary (top of block 29) has a few young wildings on the
Pukaki side, while the western third (top of blocks 25 and 28) has even
fewer, so as long as they are removed in the near future before
serious coning begins, the risk of spread will remain low.
A higher risk is present in the eastern third of the boundary (with
Ferintosh – top of blocks 16, 23 and 24), as it has spread-prone
species (contorta and Douglas-fir) right up to the fenced margin, and
there is evidence elsewhere on the station of some small movements
of seed to the north. For example, near the southern Pukaki Downs
boundary by the yards (southern end of block 31) Scots and
ponderosa pine wildings can be found out to a few hundred meters (at
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