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

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successfully on small trees close to the Musterer’s hut, but this would be difficult to repeat successfully on boggy and/or uneven ground. In addition, in order to remove all green branches at ground level, mulching must be deep, and this can expose mineral soil, which invites the reinvasion of conifers from residual seed (although a tracked digger working a mulcher head would cause less soil disturbance). Of the physical options, that using scrubbars would probably be the most cost-effective, although chainsaws would be more suitable for the isolated trees, particularly those in thick tussock. • The NW corner – eastern slopes of Rhoboro Range (block 30). As explained above, many of the trees in this area are coning and located on high altitude exposed sites. Hence, there is a high risk of seed being blown west and south onto DOC land. Means of removal. If aerial herbicides are not to be used, the only option is physical removal. The land is too steep for machines. Local DOC should be consulted on the most cost-effective technique and operators for physical removal. • A strip along the Ferintosh boundary (top of blocks 16, 17 & 24). Although the risk of seed dissemination north (from Pukaki Downs onto Ferintosh) is not high and unlikely to go far, the clearance of a 20m wide strip is recommended – as much for ‘good neighbour’ reasons as anything else. Where trees are dense, the resulting thick branch slash and vigorous grass regrowth after felling should mean that new invasion of wildings will be light for a number of years. There are the options of promoting this herbaceous grass growth by oversowing seed and adding fertilisers, or of preventing wilding reinvasion by planting a less spread-prone tree species (see containment options below). Means of removal. If aerial herbicides are not to be used, the only option is physical removal. Much of the land is too steep and uneven for machines, plus many of the trees are large – although a tracked digger working a mulcher head, could do a good job. Local DOC should be consulted on the most cost-effective technique and operators for physical removal. • Blocks 13 and northern half of 19. These are low priority, as they are close to the thicker and more mature contorta wildings in block 11 and the southern half of block 19 ( and hence more susceptible to the arrival of new seed). However, with the prevailing strong winds from the north, the risks of re-invasion from outside seed sources are lower than further to the south and east. Although there are considerable numbers of wildings currently present, most are small and only just starting to cone. If the area was to be cleared of wildings, their replacement with a less-spread-prone woody cover is recommended – due to the higher risk of reinvasion by seed from the adjacent contorta stands to the east. Means of removal. If aerial herbicides are not to be used, the main other option is physical removal. Much of the land is probably too uneven for machines, although a tracked digger working a mulcher head, could do a good job on the patches of dense trees. Local DOC should be consulted on the most cost-effective technique and operators for physical removal. • Eastern scarp slopes of Little Rhoboro Hills (block 20 and the steeper parts of block 14). This area is the last priority for control. As explained above, even though they are relatively exposed and can be subject to strong winds, the evidence is that most seed is blown 9
south to remain within Pukaki Downs. Movement to the west is restricted by winds coming down the Twizel valley and eddying east around the end of the Rhoboro Range. In addition, most of these scarp slopes now have a dense cover of wildings, which would be both expensive to remove and to retain free of trees. Means of removal. If aerial herbicides are not to be used, the only other option is physical removal. Much of the land is too steep and uneven for machines, although a roller-crusher (as used to clear scrub in the past by the NZ Forest Service) could be operated from the top ridge. This could be followed-up by burning, as the slopes lend themselves to easier fire containment - but the resource consent proceedure required to carry out a burn could well be onerous. Local DOC should be consulted on the most costeffective technique and operators for physical removal. Containment area. This area, within which trees would remain, ties in very closely with the pink-coloured blocks on the map, with two exceptions: • The striped-pink corridor north of DOC’s Dusky Reserve (running between blocks 21/16 and blocks 17 / 22-24) should be included in the containment area, as it is surrounded by wilding contorta pine forests, and keeping it wilding-free would be a large and on-going commitment. Even if it is improved for heavier grazing (which would require fencing as well), the seed rain would be high and wilding control will become increasingly difficult to maintain. • As indicated elsewhere, the current wilding cover in western parts of blocks 12, 13 and 19 is relatively light, and where this is the case, could be removed. With the major seed disseminating winds coming from the north, wilding reinvasion would not be frequent, despite the proximity of these areas to contorta forests to the east. Options for containing conifers within managed areas The areas recommended above for the clearing of wildings were chosen to reduce the risk of wilding spread outside Pukaki Downs, and also because they had a relatively low wilding presence, which would not be too costly to remove. Other areas could also be cleared (continuing the strategy of control from the north), but clearing them and keeping them clear would be very expensive. Once the trees outside the containment area have been cleared, there are management options for minimising the risk of reinvasion. These are establishing a vegetation cover which is too dense for wilding establishment, developing and maintaining pasture for more intensive grazing, and planting a surrounding ‘shelter-belt’ of a less spread-prone tree species. • Establishment of a dense vegetation cover. This could be another woody crop (usually forest) or it might be a vigorous herbaceous cover. ~ Woody crop – usually forest. Most of the invasive conifers are too light demanding to be able to establish from seed under a closed canopy woody cover, especially if it is tall, such as a forest. Hence, one wilding prevention option for Pukaki Downs is to establish susceptible land in a new forest cover. If the area to be planted is one from which seed could be disseminated elsewhere, then a non or less spread-prone species should be chosen. This might be ponderosa or radiata pine, or a radiata x Knobcone pine (P. attenuata) hybrid on the harsher sites, or perhaps a cypress (Cupressus species, such as Leyland or Lawsons cypress) on the more benign sites, depending on the objective of the planting (timber production or carbon storage). Where the risk of spread off-site is less, then a more valuable species such as Douglas-fir could be planted. 10
Page 1 and 2: Oral Submission Presentation by Bla
Page 3: 16. The responsibility the NZ carbo
Page 6 and 7: REPORT TITLE AUTHORS CLIENT CLIENT
Page 8 and 9: Recommendations On Pukaki Downs it
Page 10 and 11: Project and client In April, 2010,
Page 12 and 13: History of wilding spread Pre 1970s
Page 14 and 15: is by the musterer’s hut at the m
Page 16 and 17: most depleted existing cover and it
Page 20 and 21: ~ Herbaceous cover. Wildings have d
Page 22 and 23: event indicates that once the Twize
Page 24 and 25: Above. The clear corridor (pink-str
Page 26 and 27: Developments from Rural Delivery we
Page 28 and 29: We have sold the carbon credits thr

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

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