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

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~ 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 11
availability and poor soil quality on much of the rest of Pukaki Downs limits the use of improved pasture and arable cropping - unless irrigation is introduced. Fertilising would enhance any grass regrowth amongst felled trees (even though no grazing would be associated) and further diminish opportunities for wilding invasion. ~ Planting of a margin of less spread-prone trees. In effect, this is what is being implemented by the containment forest planting recommended immediately above. It is recommended that the felled strips by the northern boundary with Ferintosh and in the forested areas alongside SH80 be made ‘wilding-proof’ by either fertilising to promote vigorous herbaceous growth or planting of less spread-prone species. Even though the main spread of conifer seed is from north to south, a marginal strip of trees along the southern fence-line with Rhoboro Downs station is less important, due to there either being dense forest on both sides of the boundary (the eastern half) or no trees present at all (the western half). Apart from the outer boundaries, all the fenced margins between remaining contorta pine forests and the tree-less pasture areas within the station could be planted in four rows of radiata, its hybrids or ponderosa pine – around the northern and western margins of block 31 and around the western margins of blocks 9, 12, 13 and 19. If this were to be carried out, the latter four blocks would be the priority as, although the topography on the forested side of the fence is more varied (greater risk of seed being blown from the forest canopy), the grazing pressure is generally lighter (and hence the spread risk higher) on that side of the property. Prior to any marginal strip planting, any existing contorta pine trees would have to be removed from along the fencelines. The need for this marginal 4-row planting would, of course, be negated if the contorta forests were replaced with a less spread-prone species. Areas for C storage management Described above are the areas recommended for wilding removal, those where less spread-prone species could be planted and those where the maintenance of current pasture and arable management will restrict wilding establishment. The remainder of Pukaki Downs could be managed for carbon storage. This ties in closely with the pink and pink-striped portions shown on the map (see ‘containment area’ above). Initially, the dominant species would be contorta pine, but over time it may be possible to replace these with the less spread-prone species. Discussion As there is a major tourist road (SH80) running through the property, the wilding conifer problem along the south-western shores of Lake Pukaki is well known. Unfortunately, it involves the most spread-prone conifer species, contorta pine. Although other species such as Douglas-fir, Corsican pine and larch are also involved, if contorta pine was not present, then there would be no need for this report. Wildings have been spreading since the 1960s, but the area obviously affected has only increased significantly in the last 15 years. This has been largely triggered by spread from the lake-shore plantings carried out after the lake was raised in the early 1970s - although most of the contorta forests in the south-eastern portion of Pukaki Downs originate from trees present before that time. The patterns of spread likely in the future are well indicated by the pattern of spread over the last few decades. These show that spread is mainly to the south, driven by the prevailing strong northerly winds, but that occasionally a more easterly wind can pick up and carry seed high into the air and far to the south-east. This is what appears to have happened back in the early 1990s, resulting in a scattering of wide-spread outlier trees in the upper Twizel river valley. Unfortunately, these outliers were allowed to mature and cone well before they were removed in the mid 2000s, giving rise to the islands of fringe spread so obvious today. The ‘one-off’ nature of this spread 12
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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
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Page 16 and 17: most depleted existing cover and it
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Page 24 and 25: Above. The clear corridor (pink-str
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Page 28 and 29: We have sold the carbon credits thr

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

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