Oral Submission Presentation by Blake Foster - New Zealand ...
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<strong>Oral</strong> <strong>Submission</strong> <strong>Presentation</strong><br />
<strong>by</strong> <strong>Blake</strong> <strong>Foster</strong><br />
1. Thanks for the opportunity to give a presentation to the honorable members<br />
of the select committee.<br />
2. My name is <strong>Blake</strong> <strong>Foster</strong>; I am the manager of Pukaki Downs Station near<br />
Twizel and a director of Pukaki Forestry Ltd.<br />
3. I am here to share with you how the ETS had given us hope to deal with a<br />
huge environmental problem of wilding contorta pines. But with the crash of<br />
the carbon market this is a fading memory.<br />
4. The present wilding problem on Pukaki Downs was inherited. It is huge and<br />
costs a tremendous amount of money to eradicate and control with no<br />
return on the money spent –a black hole.<br />
5. When we heard of the ETS, we knew that the funds from the ETS carbon<br />
credits would give the capital to finance the clearing of the trees and to fund<br />
re‐engineering the core forest with a non‐spreading hybrid.<br />
6. We initially commissioned a study <strong>by</strong> Nick ledgard of Scion to identify where<br />
the spread was coming from, where it was going, identify areas of low spread<br />
risk for carbon storage and develop an overall management plan. We then<br />
set about following this plan. (a copy of the plan is attached)<br />
7. A core area of wildings was registered in the ETS and the funds from the sale<br />
of these credits were used to clear the outlier wildings‐approximately 750<br />
hectares outside the core area in the last few years.<br />
8. Last year, Rural Delivery TV show, heard of our innovative way to deal with<br />
the wilding spread <strong>by</strong> using the ETS funds from Carbon Credits in one area to<br />
control the spread in another. They came and did a segment. Here is the link<br />
to that video segment http://tvnz.co.nz/rural‐delivery/s2011‐e28‐video‐
4454527 Here is a link to the written press release <strong>by</strong> Rural Delivery about<br />
this video segment<br />
http://www.ruraldelivery.net.nz/2011/10/wilding‐pine‐control/<br />
9. The 15 yr plan is to change or re‐engineer the core wilding spread <strong>by</strong> clearing<br />
it and replanting with a non‐spreading species. We were going to be clearing<br />
80 hectares a year.<br />
10. Our attempt to clear the contorta wildings is coming to a standstill due<br />
to the Carbon legislation in NZ ETS not supporting the local forestry and<br />
carbon industry <strong>by</strong> allowing the emitters to buy cheap units from overseas<br />
and not having a regulation like Australia does with 50% cap of buying local.<br />
11. Buying local credits would not only help our current account deficit <strong>by</strong><br />
stopping money going overseas to buy cheap credits but bring in tax revenue<br />
locally when local credits are purchased.<br />
12. We were employing up to 50‐60 people directly or indirectly‐clearing<br />
gangs, planters and nurseryman transport operators. This has now virtually<br />
stopped. Planting programs are long term commitments of at least two years<br />
13. Some may say this is just market correction and that the goverment<br />
shouldn’t get involved. The government has already intervened <strong>by</strong> giving the<br />
emitters a two for one deal. The emitters have been given 90% of the units<br />
and now only have to pay 5% of the 10 they were to buy. The emitters can<br />
buy the cheapest credits possible. We are asking that the NZ Carbon forest<br />
industry needs to be stabilized. This can be done very simply <strong>by</strong> aligning<br />
ourselves with the Australian system.<br />
14. I request the committee to seriously look at aligning the NZETS with<br />
the Australian system <strong>by</strong> having a 50% cap on international units and 12.5%<br />
CERs.<br />
15. If wildings are entered into the ETS with a proper management plan<br />
this should be seen as positive.
16. The responsibility the NZ carbon market is in your hands. If there is not<br />
a change soon there won’t be a carbon market in NZ.
CLIENT REPORT (Confidential)<br />
Wilding conifer spread on Pukaki Downs station:<br />
origin, future spread risks and management options<br />
Contorta pine wildings invading terrace country on Pukaki Downs station, with Lake Pukaki behind – taken in 2008.
REPORT TITLE<br />
AUTHORS<br />
CLIENT<br />
CLIENT CONTRACT<br />
NO:<br />
FRST CONTRACT<br />
NO:<br />
SIDNEY OUTPUT<br />
NUMBER<br />
SIGNED OFF BY<br />
DATE<br />
CONFIDENTIALITY<br />
REQUIREMENT<br />
INTELLECTUAL<br />
PROPERTY<br />
REPORT INFORMATION SHEET<br />
WILDING PINE MANAGEMENT ON PUKAKI DOWNS<br />
NICK LEDGARD, SCION<br />
PUKAKI TOURISM HOLDINGS LTD<br />
QUIKTRAK NUMBER QT-1372<br />
NONE<br />
MAY 18, 2010<br />
CONFIDENTIAL (FOR CLIENT USE ONLY)<br />
MICHAEL WATT, PROJECT LEADER, WEEDS<br />
© NEW ZEALAND FOREST RESEARCH INSTITUTE LIMITED<br />
ALL RIGHTS RESERVED. UNLESS PERMITTED BY CONTRACT OR LAW,<br />
NO PART OF THIS WORK MAY BE REPRODUCED, STORED OR COPIED<br />
IN ANY FORM OR BY ANY MEANS WITHOUT THE EXPRESS PERMISSION<br />
OF THE NEW ZEALAND FOREST RESEARCH INSTITUTE<br />
LIMITED (TRADING AS SCION).<br />
Disclaimer<br />
The information and opinions provided in the Report have been prepared for the Client and its specified<br />
purposes. Accordingly, any person other than the Client uses the information and opinions in this report<br />
entirely at its own risk. The Report has been provided in good faith and on the basis that reasonable<br />
endeavours have been made to be accurate and not misleading and to exercise reasonable care, skill<br />
and judgment in providing such information and opinions.<br />
Neither Scion, nor any of its employees, officers, contractors, agents or other persons acting on its behalf<br />
or under its control accepts any responsibility or liability in respect of any information or opinions provided<br />
in this Report.
EXECUTIVE SUMMARY<br />
The problem<br />
Wilding conifers have been invading Pukaki Downs station since the early 1960s . Initially, invasion was<br />
restricted to a short section of the lakeshore <strong>by</strong> the Homestead, but more extensive invasion started to<br />
take hold in the late 1980s / early 1990s. The main spreading species is Lodgepole or contorta pine<br />
(Pinus contorta), the country’s most vigorous spreading conifer. At the present time, wildings are<br />
approaching canopy closure over approximately 30-40% of the station, with much of the remaining area<br />
affected <strong>by</strong> widely scattered outlier trees (often accompanied <strong>by</strong> patches of fringe spread). If left<br />
unmanaged, wildings would dominate the majority of Pukaki Downs. Hence, the owners are attempting<br />
to manage the spread <strong>by</strong> containment within the areas least likely to spread further, and removal of<br />
wildings from areas with higher risk of distant spread.<br />
Client Initiative<br />
In April, 2010, Nick Ledgard (NL) of Scion in Christchurch was asked <strong>by</strong> <strong>Blake</strong> <strong>Foster</strong> of Pukaki Tourism<br />
Holdings Ltd to carry out a field inspection and write a report on the wilding conifer situation and<br />
management options on Pukaki Downs station. NL visited the station from May 30 – June 2, 2010, after<br />
which he wrote this report.<br />
The project<br />
The major objectives of this report are to describe:<br />
a) the history of conifer spread, its origin and present location<br />
b) the likely future spread risk and pattern if left unmanaged<br />
c) priority control areas for minimising spread risk beyond present locations (particularly off-station)<br />
d) options for containing conifers within the managed areas.<br />
e) areas with least spread risk which could be managed for carbon storage.<br />
Key Findings<br />
o The wilding conifer problem along the south-western shores of Lake Pukaki is well<br />
known, situated alongside a major tourist route (SH80). Unfortunately, it involves<br />
the most spread-prone conifer species, contorta pine.<br />
o Wildings have been spreading since the 1960s, but the area obviously affected<br />
has only increased significantly in the last 15 years. This has been largely<br />
triggered <strong>by</strong> spread from the lake-shore plantings carried out after the lake was<br />
raised in the early 1970s, although most of the contorta forests in the southeastern<br />
portion of Pukaki Downs originate from trees present before that time.<br />
o The pattern of spread likely in the future is well indicated <strong>by</strong> the pattern of spread<br />
over the last few decades. These show that spread is mainly to the south, driven<br />
<strong>by</strong> the prevailing strong northerly winds, but that occasionally a more northeasterly<br />
wind can pick up and carry seed high into the air and more to the west.<br />
o Such an event in the early 1990s gave rise to outlier wildings in the upper Twizel<br />
river catchment, which were allowed to mature and cone before they were<br />
removed in the mid 2000s, giving rise to the islands of fringe spread so obvious<br />
today.<br />
o The ‘one-off’ nature of this spread event indicates that once the Twizel river flats<br />
are cleared, they should not be re-invaded often and hence should not be too<br />
difficult to keep clear in the future – as long as any wilding trees which do establish<br />
are removed before age 5-6, when they begin coning.<br />
o This ‘stitch-in-time-saves-nine’ maxim must always be kept foremost in any<br />
management plan.<br />
o Within the wilding cleared zones, a containment area of trees will remain.<br />
o Removal sweeps outside the containment area will be needed at least every 4<br />
years for as long as seeding contorta pine trees remain in the locality.<br />
o The incidence of re-invasion, and need for timely removal, should be diminished <strong>by</strong><br />
the control and containment management options recommended below.<br />
(i)
Recommendations<br />
On Pukaki Downs it is recommended that:<br />
• All wildings be removed in the near future from the upper Twizel river catchment<br />
(blocks 25-29), except in the most densely forested areas in the eastern margin of<br />
that area (blocks 9-13 plus 19).<br />
• All wildings should also be removed from block 29, although planting it with a less<br />
spread-prone species is an option.<br />
• All wildings be removed from the steep slopes of the Rhoboro Range in the most<br />
north-western part of the station (block 30).<br />
• All wildings be removed in a 20m strip along the northern boundary with Ferintosh<br />
station and in a similar strip alongside SH80.<br />
• If finances allow (last priority) all wildings be removed from the steeper eastern<br />
scarp slopes (northern portion) of the Little Rhoboro Hills (block 20 and steeper part<br />
of 14).<br />
• Improved pasture and associated grazing (and/or arable cropping) be maintained<br />
where it is currently stopping wilding establishment - blocks 31 and 32 (both sides of<br />
SH80) and further to the west in parts of block 25). The north-eastern margin of<br />
block 31 would run out from the northern margin of DOC’s Dusky Reserve in order<br />
to maintain a treeless pasture margin.<br />
• Replacement plantings of less spread-prone species, such as radiata pine, its<br />
hybrid with Knobcone pine (P.radiata x P. attenuata) or ponderosa pine, be carried<br />
out along the eastern margins of the cleared areas in the upper Twizel river valley,<br />
either as 4-row marginal plantings along the western edges of blocks 9, 12, 13 and<br />
19 (if retained in contorta pine), or as whole block replacement.<br />
• Replacement plantings of less spread-prone species, such as radiata pine, its<br />
hybrid with Knobcone pine (P.radiata x P. attenuata) or ponderosa pine (minimum<br />
of 4 rows), could also be carried out along the western margins of the lakeshore<br />
contorta pine forests in the south-eastern part of block 32. This will not be<br />
necessary where ponderosa or Corsican pine make up the current margin, or where<br />
adjacent pasture cover and grazing pressure is sufficient to stop significant<br />
establishment of wildings.<br />
• Replacement plantings or fertilising be carried out in the 20m marginal strips along<br />
the Ferintosh boundary (top of blocks 16 and 24) and alongside SH80.<br />
• Marginal strips (4 rows wide) be planted along the fenced north and western<br />
margins of the tree-less pasture-dominated block 31.<br />
• Blocks 9-24 (the pink and pink-striped areas on the map), including the corridor<br />
north of the Dusky Reserve between blocks 21 / 16 and 17 / 22 – 23, will become<br />
the containment area and could be managed for carbon storage. Initially, the<br />
dominant species would be contorta pine, but over time the aim should be to<br />
replace these with less spread-prone species.<br />
• Wilding removal sweeps be carried out before coning age (no more than 4 years<br />
apart) on all cleared or otherwise tree-less areas.<br />
• Long-term planning be initiated to ensure that the above to be implemented.<br />
ii
Table of Contents<br />
Wilding spread on Pukaki Downs station:<br />
Origin, future spread risks and management options<br />
Nick Ledgard<br />
Scion<br />
PO Box 29237, Fendalton, Christchurch 8540<br />
June, 2010<br />
EXECUTIVE SUMMARY -----------------------------------------------------------------------------------i<br />
Project and client ------------------------------------------------------------------------------------------1<br />
Introduction --------------------------------------------------------------------------------------------------1<br />
Objectives ----------------------------------------------------------------------------------------------------1<br />
Methods -------------------------------------------------------------------------------------------------------2<br />
Main findings ------------------------------------------------------------------------------------------------2<br />
Spreading species----------------------------------------------------------------------------------------2<br />
History of wilding spread--------------------------------------------------------------------------------3<br />
Likely future spread with no further management------------------------------------------------6<br />
Priority control areas for minimising spread risk beyond present locations (particularly<br />
off-station) --------------------------------------------------------------------------------------------------7<br />
Options for containing conifers within managed areas --------------------------------------- 10<br />
Assisting containment on Pukaki Downs. -------------------------------------------------------- 11<br />
Areas for C storage management------------------------------------------------------------------ 12<br />
Discussion ------------------------------------------------------------------------------------------------- 12<br />
Recommendations -------------------------------------------------------------------------------------- 13<br />
Acknowledgement--------------------------------------------------------------------------------------- 14
Project and client<br />
In April, 2010, Nick Ledgard (NL) of Scion in Christchurch was asked <strong>by</strong> <strong>Blake</strong> <strong>Foster</strong> of<br />
Pukaki Tourism Holdings Ltd to carry out a field inspection and write a report on the<br />
wilding conifer situation and management options on Pukaki Downs station. NL visited<br />
the station from May 30 – June 2, 2010, after which he wrote this report.<br />
Introduction<br />
Wilding conifers have been invading Pukaki Downs station since the early 1960s .<br />
Initially, invasion was restricted to a short section of the lakeshore <strong>by</strong> the Homestead, but<br />
more extensive invasion started to take hold in the late 1980s / early 1990s. The main<br />
spreading species is Lodgepole or contorta pine (Pinus contorta), the country’s most<br />
vigorous spreading conifer. At the present time, wildings are approaching canopy closure<br />
over approximately 30-40% of the station, with much of the remaining area affected <strong>by</strong><br />
widely scattered outlier trees (often accompanied <strong>by</strong> patches of fringe spread). If left<br />
unmanaged, wildings would dominate the majority of Pukaki Downs. Hence, the owners<br />
are attempting to manage the spread <strong>by</strong> containment within the areas least likely to<br />
spread further, and removal of wildings from areas with higher risk of distant spread.<br />
Authors credentials<br />
• Nick Ledgard obtained a BSc (Botany) from Auckland, and an MSc<br />
(Forestry) from Bangor College of the University of Wales.<br />
• He has been employed as a scientist with Scion since 1971. His specialist<br />
research area is in production and protection forestry in the South Island hill<br />
and high country.<br />
• Since the early 1980s, he has carried out a number of research projects on<br />
conifer natural regeneration or wilding spread. Refereed papers on this<br />
topic have been published both locally and overseas. From 2006 to the<br />
present day he has managed a wilding project for the South Island (now the<br />
<strong>New</strong> <strong>Zealand</strong>) Wilding Conifer Management group.<br />
• He has given numerous presentations, and organised many workshops and<br />
field-days on wilding spread issues, and written twenty contract reports on<br />
the topic. Most of these have dealt with local histories of wilding spread, the<br />
current situation and future management options.<br />
• He privately manages 380 ha of wilding Corsican pines (near L. Coleridge)<br />
for environmental (including spread control) and production objectives.<br />
Objectives<br />
The major objectives of the report are to describe:<br />
1. The history of conifer spread, its origin and present location.<br />
2. The likely future spread risk and pattern if left unmanaged.<br />
3. Priority control areas for minimising spread risk beyond present locations<br />
(particularly off-station).<br />
4. Options for containing conifers within the managed areas.<br />
5. Areas with least spread risk which could be managed for carbon storage.<br />
1
Methods<br />
A total of 2.5 days were spent on Pukaki Downs station and in the surrounding area (May 31 –<br />
June 2, 2010). Most of this time was spent in the company of <strong>Blake</strong> <strong>Foster</strong> of Pukaki Downs<br />
station. A short time was also spent talking to Gill Seymour of Ferintosh station, and Peter<br />
Willemse and Neil Bolton of the Department of Conservation, Twizel. In addition, NL has been<br />
familiar with the wilding situation on Pukaki Downs and within the Mackenzie Basin since the<br />
1970s, and has studied and written reports on the topic.<br />
Useful documents and other material consulted were:<br />
• Department of Lands and Survey, 1985: Trees planted in association with<br />
power development in the mid and upper Waitaki 1958-1984. Technical<br />
Report Series No 1, Department of Lands and Survey, Dunedin. Copy held<br />
<strong>by</strong> Alexander Turnbull Library, Wellington.<br />
• Maps and aerial photos supplied <strong>by</strong> Pukaki Downs station and Carbon Farm<br />
Ltd.<br />
• Photos supplied <strong>by</strong> Pukaki Downs station and from NL’s collection.<br />
• Ledgard, N.J.; Baker, G.C 1997: Management options for introduced trees<br />
on Ruataniwha Farm, around lakes Tekapo, Pukaki and Ruataniwha and<br />
within the Tekapo, Pukaki and Ohau rivers. Contract report for Bob Lysaght,<br />
Crown Property Services, Land Information NZ, Christchurch<br />
• Ledgard, N.J. 2004: Wilding conifers – <strong>New</strong> <strong>Zealand</strong> history and research<br />
background. In Hill, R.l.; Zydenbos, S.M.; Bezar, C.M. (Eds) “Managing<br />
wilding conifers in <strong>New</strong> <strong>Zealand</strong> – present and future”. Proceedings of a<br />
workshop held in conjunction with the annual general meeting of the NZ Plant<br />
Protection Society in Christchurch on August 11, 2003. ISBN 0-478-10842-7<br />
Published <strong>by</strong> NZPPS: 1-25<br />
Main findings<br />
Spreading species<br />
The major conifer species spreading on Pukaki Downs are given in Table 1. By far the most<br />
dominant species is contorta pine. Unfortunately, this is the most spread-prone conifer in <strong>New</strong><br />
<strong>Zealand</strong>, with the lightest seed – which can be disseminated the greatest distances.<br />
Table 1. Major spreading species on Pukaki Downs<br />
Common<br />
name<br />
Latin Name Wilding seed source Comments<br />
Lodgepole or Pinus contorta 1. Trees ‘mistakenly’ planted The most spread-prone species in NZ,<br />
contorta pine<br />
on the shores of L. Pukaki in and <strong>by</strong> far the major spreading species<br />
the 1970s. 2. Spread from (99%) on Pukaki Downs. Usually first<br />
farm homestead plantings<br />
now under the lake<br />
coning around age 5-6<br />
European larch Larix decidua 1970s lake-shore trees – plus Mostly associated with widely<br />
the earliest arrivals possibly scattered outlier wildings, a number of<br />
<strong>by</strong> seed from old stand near which now have fringe spread.<br />
mouth of Whale Stream Spreading from age 15<br />
Douglas-fir Pseudotsuga Mostly from lake-shore trees Most wildings under age 12 and still<br />
menziesii<br />
planted in the 1970s – plus close to lakeside seed source. Likely<br />
some from earlier farm to become much more frequent in the<br />
plantings<br />
future. Coning from age 8-10.<br />
Corsican pine Pinus nigra Lake-shore trees associated Surprisingly few wildings west of<br />
with early homestead<br />
SH80 (oldest seen aged 20). A shy<br />
plantings<br />
coner before age 20.<br />
Scots pine Pinus sylvestris Short shelterbelt <strong>by</strong> yards – Only localised spread, mainly to south.<br />
planted in 1970s<br />
Coning from age 10+<br />
Ponderosa pine Pinus ponderosa Shelterbelt <strong>by</strong> yards, plus A little localised spread. Coning from<br />
homestead trees – planted in<br />
1970s<br />
age 12+. Not a major threat.<br />
Radiata pine Pinus radiata Homestead plantings, plus a Very few wildings seen. Coning from<br />
few old trees <strong>by</strong> Dusky site age 10+. Not a major threat.<br />
2
History of wilding spread<br />
Pre 1970s. Very few trees were present on Pukaki Downs station before the 1970s.<br />
From photos taken prior to that time and talks with local people, it appears that small<br />
areas of trees (nearly all introduced conifers) were present around the early lake-side<br />
station homesteads at Dusky, Mackenzie Peaks, and Pukaki Downs. Most of these trees<br />
were submerged when L. Pukaki was raised in the early 1970s. On the area presently<br />
occupied <strong>by</strong> Pukaki Downs station, Lodgepole or contorta pine (Pinus contorta) and<br />
Corsican pine (P. nigra) must have been growing somewhere at or between Mackenzie<br />
Peaks and Pukaki Downs stations, as both species were present as wildings alongside<br />
the shores of the lake after it was raised. A plot established <strong>by</strong> NL in the contorta pine in<br />
1983 contained trees aged 22. Five kilometres to the west on the Twizel River flats, the<br />
only current evidence of ‘early’ introduced trees are three felled contorta pine <strong>by</strong> the<br />
musterer’s hut at the junction of Gladstone Stream and the Twizel river. One tree was<br />
aged at 50 years old when felled in the early 2000s.<br />
To the north, on the present Ferintosh station, there were radiata pine (P. radiata),<br />
European larch (Larix decidua) and Douglas fir (Pseudotsuga menziesii) present when the<br />
lake was raised. All three species were probably planted, but larch was moving down the<br />
lake shore (G. Seymour, pers comm.), most likely establishing from seed from trees<br />
planted possibly over 100 years ago, just north of the Ferintosh homestead <strong>by</strong> the mouth<br />
of Whale Stream.<br />
To the south on Rhoborough Downs, a plantation of Douglas-fir was present<br />
alongside the lake just north of the current dam site. The upper-most parts of this<br />
remained above the lake (aged at 27 years in 1983 – NL plots), from which spread has<br />
occurred since. Also on Rhoborough Downs and close to the Pukaki Downs boundary<br />
was a stand of Corsican and ponderosa pine and European larch planted <strong>by</strong> a water<br />
reservoir around the 1960s. These have also spread to the south since (but not nearly as<br />
vigorously as the contorta pine), and no evidence was seen that they have spread north<br />
onto Pukaki Downs (lack of Corsican pine wildings near boundary).<br />
1970s. With the raising of the lake, began a period of lakeshore tree establishment<br />
<strong>by</strong> the Ministry of Works and Development (MOWD). The trees were planted to slow<br />
erosion of the newly formed lakeshore banks and also for ‘amenity’ purposes. The first<br />
recording of ‘Pukaki’ planting was in 1970, with the first mention of Pukaki Downs in 1972.<br />
The 1985 Dept of Lands and Survey report on the MOWD plantings records that 10,500<br />
‘Pinus species (mixed)’ were planted on Pukaki Downs in 1977. This planting went on<br />
into the early 1980s (completed in 1983). Virtually all these trees were established<br />
between the highway (SH80) and the lakeshore, from Jack Steel Stream to just north of<br />
Boundary Stream, on land which is now administered <strong>by</strong> Land Information <strong>New</strong> <strong>Zealand</strong><br />
(LINZ). One exception was some shelterbelt trees planted further south on the western<br />
side of the road, close to the current Pukaki Downs yards. The main species present<br />
there are Corsican, ponderosa, Scots (Pinus sylvestris) and Big Cone pine (P. coulteri),<br />
but mixed in with these is a small component of contorta pine.<br />
The MOWD plantings on LINZ land involved a wide range of species, often planted<br />
as individuals or small groups, but also including larger plantations (a few hectares) of<br />
larch, Douglas-fir and Big Cone pine, established in the early 1980s. About this time,<br />
there were additional amenity tree plantings of widely spaced deciduous trees, such as<br />
oak (Quercus spp), ash (Fraxinus spp) and rowan Sorbus spp).<br />
In the MOWD report, the last mention of contorta pine was in 1965. This was at the<br />
time when there was some publicity about the spreading tendency of this species,<br />
especially in the Central Plateau area of the North Island. Consequently, it was resolved<br />
that there should be no more planting of this species in the upper Waitaki catchment.<br />
However, there is strong circumstantial evidence that there was a ‘contaminant’ of<br />
contorta pine in the mixed conifer species which were supplied for planting in the 1970s.<br />
These probably explain the 35-year-old contorta trees which are still growing between the<br />
highway and the lake - seen <strong>by</strong> NL between Big Rock Stream and the old Dusky<br />
3
homestead trees (but they were also present further north on the lake shore – removed<br />
some years ago – G. Seymour, pers comm).<br />
It is very likely that most of the contorta wildings currently on Ferintosh and the<br />
northern half of Pukaki Downs originated from the ‘mistake’ plantings established on<br />
‘LINZ’ land <strong>by</strong> the lake shore in the mid 1970s . The contorta wildings on the southern<br />
half of Pukaki Downs most probably established from seed blown from the older and<br />
much denser lake-side stands of contorta pine growing closer to the homestead – along<br />
the eastern lakeshore margins of block 32.<br />
1980s. Apart from fringe spread alongside the wilding forests <strong>by</strong> the eastern<br />
lakeshore margins of block 32 (in the south-eastern part of Pukaki Downs), wilding trees<br />
in the 1980s would not have been very apparent to those not deliberately looking for them.<br />
One has to look fairly hard at 1986 aerial photographs to see evidence of wildings.<br />
Although the older lake-side forests close to the homestead are obvious, 10-year old<br />
plantations on LINZ land north of the northern boundary can only just be seen. Just a<br />
kilometre or so further north again, a closer inspection of the photo reveals scattered trees<br />
(most likely contorta pine) along the lakeshore south of Big Rock Stream, plus a few<br />
outlier trees with small downwind (S side) areas of fringe spread at the top of blocks 16<br />
and 24. Even closer inspection can just detect the odd lone tree in the northern parts of<br />
the middle terrace flats, the most obvious of the larger ones looking like larch – both on<br />
the flats and the steep scarp slope running up onto the Little Rhoboro Hills.<br />
1990s. During this decade, the major battles with wilding spread were waged in the<br />
south eastern part of the property (block 32) along the western margins of the lakeshore<br />
wilding forests – although higher sheep numbers meant that there was not much new<br />
recruitment of wildings at that time. Plantings of less spread-prone ponderosa and<br />
Douglas-fir were carried out along these forest margins, probably in order to restrict this<br />
fringe spread. It appears that during the 1980s and 90s some seed from these contorta<br />
stands blew over SH80 in a south-westerly direction to give rise to the denser wilding<br />
stands in blocks 9 and 10, west of the airstrip, not far above the Rhoboro Downs<br />
boundary.<br />
Elsewhere on the station, wilding trees were still not obvious - an NL slide (from the<br />
air) of the Big Rock Creek stream area (top of blocks 16 and 24) taken in 1990, shows<br />
very few conifers – although two have discernable fringe spread. However, it was in this<br />
decade that the foundations were laid for the later major advance of wildings elsewhere<br />
on the property. Many of the older scattered trees which were seen (and found felled) all<br />
over Pukaki Downs, particularly in the north and western parts (and out onto neighbouring<br />
DOC land) can be aged back to an arrival date around 15-20 years ago – indicating that<br />
they arrived in the early 1990s. Even though they would have been present as small<br />
seedlings, there is no sign of these trees in an NL slide taken in the Twizel catchment in<br />
1993, when the present owner was showing the area to forest company representatives<br />
looking for afforestation opportunities. As stated above, all the evidence points to these<br />
outlier wildings having established from seed disseminated from the MOWD lakeside<br />
contorta ‘mistake’ plantings established in the early/mid 1970s. The fact that they are<br />
widely scattered out to a distance of 10kms indicates that the seed was lifted high before<br />
dropping in a widely scattered ‘salt and pepper-like’ distribution. The wind carrying the<br />
seed must have had more of a north-easterly flow than usual, as some were carried right<br />
‘around the corner’ of the Rhoboro Hills (over the Little Rhoboro Hills ridge) and up into<br />
the junction area of the Duncan and Mackenzie Streams (the topmost tributaries of the<br />
Twizel River). Such a wind-flow pattern is different from the normal prevailing nor-west<br />
winds (see ‘2000s on’ below). It is these trees which have given arise to the very obvious<br />
‘islands’ of fringe spread (often between 500 – 1000 m 2 in size), currently aged around 5-6<br />
years old (and just starting to cone). The majority of the scattered outlier parent wilding<br />
trees were removed between 2004-2008, but not before they had produced viable seed<br />
and initiated the present islands of 5-6 year olds. In the upper Twizel river area there is<br />
one major exception to the wilding origin being the Lake Pukaki shoreline plantings. This<br />
4
is <strong>by</strong> the musterer’s hut at the mouth of Gladstone Stream (block 26), where a few<br />
contorta trees were planted over 50 years ago. They were felled in the early 2000s (the<br />
oldest at age 50), but <strong>by</strong> then they had parented an area of fairly dense wildings over<br />
some hectares to the south. Many of these had been allowed to reach coning age before<br />
they were felled.<br />
2000s. The most obvious increase in wilding numbers on Pukaki Downs has taken<br />
place since 2000. This is largely due to progeny of the outliers which arrived in the early<br />
1990s becoming very obvious – mostly as fringe spread ‘islands’ but also in the form of<br />
same-aged outliers beyond the ‘island’ borders. An NL slide of the Little Rhoboro Hills<br />
east-facing scarp slopes (block 14) taken in 2003 shows the first of the larger fringespread<br />
‘islands’ starting to become very obvious. The direction of spread of the fringe<br />
wildings out from their parent trees strongly indicates a wind-flow pattern from the north.<br />
On Pukaki Downs, there are two origins of this northerly wind – one from down the lake<br />
and the other, on the western side of the Rhoboro Hills, from the Twizel river headwaters.<br />
Spread in the upper Twizel river catchment is generally north to south, but on the western<br />
side and on top of the Little Rhoboro Hills ridge it has more of a south-easterly flow as the<br />
taller Rhoboro Range mountains to the north drop sufficiently to allow an eddy of wind to<br />
the east. Along the ridge of the Little Rhoboro Hills, the Twizel River and lake wind flows<br />
meet and move together to the south.<br />
Age classes of wilding conifers. A feature of wilding spread on Pukaki Downs<br />
and Ferintosh is the uniformity of wilding ages. The commonest age is 5-6 years – trees<br />
which are progeny of the outliers which arrived in the early 1990s. The uniformity of tree<br />
age is particularly striking where relatively closely-spaced parent trees were felled, often<br />
when they were 10-12 years old. This ‘flush’ of new wildings which appears to occur after<br />
parent-tree felling, has been observed on Pukaki Downs (and elsewhere) for some time.<br />
The reason for this ‘flush’ is not clear. As contorta can first start to cone at age 5-6 years<br />
of age, and there are many of this age-class present, there is obviously a great risk of a<br />
new wave of wildings appearing in the near future – although the viability of seed<br />
produced before age 10 is thought to be lower than when the trees are more mature.<br />
Coning age. A summary of age of significant coning per species is given in Table<br />
1. A small minority of trees will always start coning earlier. However, there is strong<br />
suspicion that the earliest produced seed does not have as high viability as seed<br />
produced later. Work is underway to confirm this. It is also known that the first obvious<br />
appearance of wildings often occurs quite a few years after the first seed is produced. For<br />
instance, on Pukaki Downs it seems that significant numbers of wilding contorta do not<br />
appear much before age 10, even though cones are often produced from age 5-6.<br />
Prevailing wind flows. As explained above, the direction of wilding appearance<br />
out from a parent tree indicates the direction of the most common seed dispersing winds.<br />
On Pukaki Downs these winds blow from the north. They are also the warmest, which is<br />
important for wilding spread, as the cones open in warm conditions. As the Rhoboro Hills<br />
are oriented north-south, the wind blows down both sides of the range, with the Twizel<br />
river flow diverting more to the east before joining the lakeside flow over the Little Rhoboro<br />
Hills and heading on south. Even though there is strong evidence for this wind flow<br />
pattern, there is also evidence that the occasional strong winds can blow more from the<br />
north east. Such a wind was responsible for the major spread event in the early 1990s,<br />
which disseminated seed from the lakeshore parents to establish widely separated lone<br />
wildings in and around the upper Twizel river flats<br />
Frequency of spread events. The age of wilding trees enables any observer to<br />
obtain a good estimate of when the seed arrived. However, in addition to the winds<br />
needed to disseminate seed to a suitable site, successful seed germination and seedling<br />
establishment requires a growing season without extremes of moisture stress and<br />
5
temperature or unseasonal frosts, as well as light grazing/browsing pressure (from both<br />
domestic and wild animals). The evidence from many wilding spread areas throughout<br />
<strong>New</strong> <strong>Zealand</strong> is that this set of circumstances do not happen nearly as frequently as many<br />
people think - as wildings often appear in uniform age classes separated <strong>by</strong> many years.<br />
This is the case at Pukaki Downs. Even though the major seed source beside the lake<br />
has been producing contorta pine seed since the early 1980s, there appears to have been<br />
just one event (in the early 1990s) which allowed wildings to become established out to 10<br />
km to the west (on the Twizel river flats). There is no certainty when such events will<br />
occur, but time and again this author has seen them happening between 15-20 years<br />
apart, sometimes earlier if contorta pine is involved.<br />
Susceptibility of land to wilding establishment. Wilding conifers establish most<br />
readily on lightly vegetated and lightly grazed land. They are least likely to establish<br />
where the vegetation cover is thick (herbaceous and woody) and/or where animal grazing<br />
is medium to heavy. Rabbit numbers can have a major negative effect on wilding<br />
establishment, and in the high country the arrival of rabbit haemorrhagic disease in 1997<br />
heralded a significant rise in seedling numbers. However, sheep have been the main<br />
grazing influence on Pukaki Downs. Even a low stocking pressure of around 0.5 stock<br />
units per hectare will significantly decrease wilding establishment, but only while the seed<br />
rain is light and infrequent. Once the seed rain becomes heavy, higher animal stocking<br />
rates are required to prevent seedling establishment – they are especially difficult to<br />
remove with grazing once they become woody (usually at 2 years of age).<br />
Herbaceous growth following conifer felling. In the high country it is well known<br />
that after the felling of conifers, the growth of herbaceous species (particularly grasses)<br />
within the ‘carcass’ of the felled tree can be vigorous - as long as the slash is not too thick,<br />
preventing light from reaching the ground surface. This increase in vigour is due to a<br />
‘flush’ of nutrients released from decaying needles and bark, combined with the sheltered<br />
microclimate created <strong>by</strong> the slash. The resulting vigorous grass growth can prevent the<br />
establishment of a new crop of wildings (or any woody species for that matter) for a<br />
number of years. And as conifer seed does not remain viable in the ground for more than<br />
a few years, the opportunity for wilding reinvasion can be lost – as long as there is no new<br />
outside seed source available when the grass vigour declines.<br />
Likely future spread with no further management<br />
Understandably, the incidence of wilding spread on Pukaki Downs would increase<br />
significantly if no further control was exercised.<br />
Relative to this three points deserve further mentioned:<br />
• Role of more intensive land use. Wildings will always have trouble<br />
establishing in the presence of improved pasture and/or higher stock<br />
grazing pressures. Although Pukaki Downs does not lend itself to<br />
large-scale pasture improvement, such areas do exist, the main one<br />
being in the southern mid and eastern zones (blocks 31 and 32), with<br />
a smaller area of thicker pasture swards on flat land to the west on the<br />
Twizel river flats (southern end of block 25). Parts of these areas are<br />
being worked up for an arable crop. These wilding-free areas can only<br />
be maintained if the more intensive management is continued, even if<br />
it may not be as cost-effective today to maintain the higher grazing<br />
levels of the past. It should also be noted that as seed rains get<br />
heavier (from higher seed production of adjacent trees) the likelihood<br />
of wilding invasion of less susceptible land increases.<br />
• Most susceptible land. The most susceptible land for further invasion<br />
is the western half of the property - that draining into the upper Twizel<br />
river catchment (blocks 25 to 29). This is the largest area with the<br />
6
most depleted existing cover and it has very low grazing pressure<br />
(mostly none) – plus there is good scattering of young wildings just<br />
approaching the age of serious coning.<br />
• Phases of spread. Even though wilding numbers will increase in an<br />
unmanaged situation, there is likely to be a ‘lull’ in the invasion rate<br />
during the next few years. This is due to many of the coning outlier<br />
trees (which arrived in the early 1990s and gave rise to the present<br />
islands of fringe spread) having been removed, and their progeny still<br />
having a few years to reach the age of significant coning. In addition,<br />
the occurrence of ‘outlier’ invasions (from distant seed sources) is not<br />
frequent, so it may well be some years before there are new wildings<br />
appearing from that source.<br />
The dominant spreading species will remain contorta pine, but there is likely to be an<br />
increase in the numbers of Douglas-fir. The spreading vigour of this species has<br />
increased significantly over the last couple of decades, probably due to the more<br />
widespread occurrence of the symbiotic mycorrhizas which are so important for early<br />
seedling survival and growth. In addition, it has a light seed which is borne in cones which<br />
hang from the ends of branches, well displayed for the dispersal of seed <strong>by</strong> passing<br />
winds. At present there are many mature Douglas-fir trees between SH80 and the lake,<br />
and those already on Pukaki Downs are into their early years of seed production.<br />
Priority control areas for minimising spread risk beyond present<br />
locations (particularly off-station)<br />
Boundary risks<br />
Looking at the north, east, south and western boundaries of Pukaki Downs, the risk of<br />
spread off-station varies from virtually zero to high.<br />
• Northern boundary. This boundary is a long and irregular one,<br />
stretching over 8 kilometers and bounding with Ferintosh station to the<br />
east and DOC to the west. With the strongest prevailing winds coming<br />
from the north down either side of the Rhoboro Range, the risk of seed<br />
dissemination in that direction is generally low. This is supported <strong>by</strong><br />
fringe spread around older trees in the area all being to the south.<br />
Having stated as much, the boundary does run from north-east to<br />
south-west, and the spread event of the early 1990s (see above) has<br />
shown that seed can be disseminated to the west – although<br />
infrequently. In addition, there are coning contorta pine high up (to<br />
900m asl) on the Rhoboro Range slopes in the northern most corner<br />
of Pukaki Downs (block 30) which could quite easily throw seed to the<br />
south-east over the Range onto DOC land in the upper Twizel river<br />
catchment - where the low vegetation cover and zero grazing pressure<br />
allows for ready wilding establishment. The middle third of this<br />
northern boundary (top of block 29) has a few young wildings on the<br />
Pukaki side, while the western third (top of blocks 25 and 28) has even<br />
fewer, so as long as they are removed in the near future before<br />
serious coning begins, the risk of spread will remain low.<br />
A higher risk is present in the eastern third of the boundary (with<br />
Ferintosh – top of blocks 16, 23 and 24), as it has spread-prone<br />
species (contorta and Douglas-fir) right up to the fenced margin, and<br />
there is evidence elsewhere on the station of some small movements<br />
of seed to the north. For example, near the southern Pukaki Downs<br />
boundary <strong>by</strong> the yards (southern end of block 31) Scots and<br />
ponderosa pine wildings can be found out to a few hundred meters (at<br />
7
most) to the north of a shelterbelt of those species. Therefore, some<br />
seed may well fall to the north of the eastern section of the northern<br />
boundary, but while seeding trees are growing near<strong>by</strong> on Ferintosh<br />
station (and presently there are many), they remain the most likely<br />
origin of any new wildings which may appear.<br />
• Eastern boundary. Apart from spread onto the road margin, which is<br />
regularly controlled <strong>by</strong> contract spraying from the highway (SH80), the<br />
risk of future spread here is very low. This is due to the presence of<br />
the lake and the fact that much of the ‘LINZ’ land between the highway<br />
and the lake is already well covered with forests. Even if these forests<br />
are removed, the likelihood of reinvasion will not be high (due to heavy<br />
branch slash and/or vigorous grass invasion) – unless there is<br />
significant ground disturbance exposing large tracts of mineral soil.<br />
• Southern boundary. Even though the prevailing wind flow is from<br />
north to south, and there are mature seeding conifers just inside the<br />
Pukaki Downs boundary, the risk of spread along the eastern section<br />
of this boundary with Rhoboro Downs station (south ends of blocks 9<br />
and 31) is low. This is because there is already closed-canopy forest<br />
immediately over the boundary on Rhoboro Downs. However, it is<br />
quite a different story along the western section of this boundary<br />
(south end of blocks 25 and 26), where there are virtually no trees on<br />
either side of the fenceline, and both the vegetation cover and grazing<br />
pressure over on Rhoboro Downs is light. In the middle section of this<br />
stretch, there is a high risk of spread to the south-west, from mature<br />
coning contorta pine in block 9. Further to the west, along the<br />
remainder of the southern fenceline (south end of blocks 25 and 26),<br />
although the land is very susceptible to wilding invasion, there is a low<br />
current risk, as no wildings are present close to the boundary and<br />
seed spread from more distant sources to the north are infrequent.<br />
However, the risk situation will change if conifers are allowed to seed<br />
close to the boundary.<br />
• Western boundary. Virtually all of this (blocks 26 to 28) bounds onto<br />
DOC land. The vegetation cover is light and the grazing level zero, so<br />
although the prevailing winds are more north-south than east-west,<br />
there is a risk of spread in this direction. However, this risk of spread<br />
from Pukaki Downs will remain low as long as the present scattering of<br />
contorta (mostly present as fringe-spread ‘islands’) is removed soon<br />
ie., not allowed to mature to significant coning age.<br />
Priority control (wilding removal) areas<br />
Based on the boundary risks outlined above, the major areas for control within Pukaki<br />
Downs in order of priority removal (see map) would be:<br />
• The upper Twizel river catchment - blocks 25-29. As explained<br />
above, this area is not subjected to regular arrivals of conifer seed<br />
from elsewhere. In addition, currently there are no mature trees<br />
present. However, many of the ‘islands’ of spread have trees just<br />
starting to cone, and unless these are removed in the very near<br />
future, there is a high likelihood of much wider invasion.<br />
Means of removal. Local DOC staff (based in Twizel) are very<br />
experienced in wilding removal options and should be consulted<br />
on this score. They are intending to use herbicides for much of the<br />
removal of the same type of wildings on their land. If herbicides<br />
are not favoured on Pukaki Downs, then the most obvious options<br />
are mechanical or physical removal. Burning is not recommended,<br />
due to the small size of the spread ‘islands’ and risk of the fire<br />
spreading elsewhere. Mechanical mulching has been used<br />
8
successfully on small trees close to the Musterer’s hut, but this<br />
would be difficult to repeat successfully on boggy and/or uneven<br />
ground. In addition, in order to remove all green branches at<br />
ground level, mulching must be deep, and this can expose mineral<br />
soil, which invites the reinvasion of conifers from residual seed<br />
(although a tracked digger working a mulcher head would cause<br />
less soil disturbance). Of the physical options, that using scrubbars<br />
would probably be the most cost-effective, although<br />
chainsaws would be more suitable for the isolated trees,<br />
particularly those in thick tussock.<br />
• The NW corner – eastern slopes of Rhoboro Range (block 30). As<br />
explained above, many of the trees in this area are coning and located<br />
on high altitude exposed sites. Hence, there is a high risk of seed<br />
being blown west and south onto DOC land.<br />
Means of removal. If aerial herbicides are not to be used, the only<br />
option is physical removal. The land is too steep for machines.<br />
Local DOC should be consulted on the most cost-effective<br />
technique and operators for physical removal.<br />
• A strip along the Ferintosh boundary (top of blocks 16, 17 & 24).<br />
Although the risk of seed dissemination north (from Pukaki Downs<br />
onto Ferintosh) is not high and unlikely to go far, the clearance of a<br />
20m wide strip is recommended – as much for ‘good neighbour’<br />
reasons as anything else. Where trees are dense, the resulting thick<br />
branch slash and vigorous grass regrowth after felling should mean<br />
that new invasion of wildings will be light for a number of years. There<br />
are the options of promoting this herbaceous grass growth <strong>by</strong><br />
oversowing seed and adding fertilisers, or of preventing wilding<br />
reinvasion <strong>by</strong> planting a less spread-prone tree species (see<br />
containment options below).<br />
Means of removal. If aerial herbicides are not to be used, the only<br />
option is physical removal. Much of the land is too steep and<br />
uneven for machines, plus many of the trees are large – although<br />
a tracked digger working a mulcher head, could do a good job.<br />
Local DOC should be consulted on the most cost-effective<br />
technique and operators for physical removal.<br />
• Blocks 13 and northern half of 19. These are low priority, as they<br />
are close to the thicker and more mature contorta wildings in block 11<br />
and the southern half of block 19 ( and hence more susceptible to the<br />
arrival of new seed). However, with the prevailing strong winds from<br />
the north, the risks of re-invasion from outside seed sources are lower<br />
than further to the south and east. Although there are considerable<br />
numbers of wildings currently present, most are small and only just<br />
starting to cone. If the area was to be cleared of wildings, their<br />
replacement with a less-spread-prone woody cover is recommended –<br />
due to the higher risk of reinvasion <strong>by</strong> seed from the adjacent contorta<br />
stands to the east.<br />
Means of removal. If aerial herbicides are not to be used, the main<br />
other option is physical removal. Much of the land is probably too<br />
uneven for machines, although a tracked digger working a mulcher<br />
head, could do a good job on the patches of dense trees. Local<br />
DOC should be consulted on the most cost-effective technique and<br />
operators for physical removal.<br />
• Eastern scarp slopes of Little Rhoboro Hills (block 20 and the<br />
steeper parts of block 14). This area is the last priority for control.<br />
As explained above, even though they are relatively exposed and can<br />
be subject to strong winds, the evidence is that most seed is blown<br />
9
south to remain within Pukaki Downs. Movement to the west is<br />
restricted <strong>by</strong> winds coming down the Twizel valley and eddying east<br />
around the end of the Rhoboro Range. In addition, most of these<br />
scarp slopes now have a dense cover of wildings, which would be<br />
both expensive to remove and to retain free of trees.<br />
Means of removal. If aerial herbicides are not to be used, the only<br />
other option is physical removal. Much of the land is too steep and<br />
uneven for machines, although a roller-crusher (as used to clear<br />
scrub in the past <strong>by</strong> the NZ Forest Service) could be operated from<br />
the top ridge. This could be followed-up <strong>by</strong> burning, as the slopes<br />
lend themselves to easier fire containment - but the resource<br />
consent proceedure required to carry out a burn could well be<br />
onerous. Local DOC should be consulted on the most costeffective<br />
technique and operators for physical removal.<br />
Containment area. This area, within which trees would remain, ties in very closely with<br />
the pink-coloured blocks on the map, with two exceptions:<br />
• The striped-pink corridor north of DOC’s Dusky Reserve (running<br />
between blocks 21/16 and blocks 17 / 22-24) should be included in the<br />
containment area, as it is surrounded <strong>by</strong> wilding contorta pine forests,<br />
and keeping it wilding-free would be a large and on-going<br />
commitment. Even if it is improved for heavier grazing (which would<br />
require fencing as well), the seed rain would be high and wilding<br />
control will become increasingly difficult to maintain.<br />
• As indicated elsewhere, the current wilding cover in western parts of<br />
blocks 12, 13 and 19 is relatively light, and where this is the case,<br />
could be removed. With the major seed disseminating winds coming<br />
from the north, wilding reinvasion would not be frequent, despite the<br />
proximity of these areas to contorta forests to the east.<br />
Options for containing conifers within managed areas<br />
The areas recommended above for the clearing of wildings were chosen to reduce the risk<br />
of wilding spread outside Pukaki Downs, and also because they had a relatively low<br />
wilding presence, which would not be too costly to remove. Other areas could also be<br />
cleared (continuing the strategy of control from the north), but clearing them and keeping<br />
them clear would be very expensive. Once the trees outside the containment area have<br />
been cleared, there are management options for minimising the risk of reinvasion. These<br />
are establishing a vegetation cover which is too dense for wilding establishment,<br />
developing and maintaining pasture for more intensive grazing, and planting a<br />
surrounding ‘shelter-belt’ of a less spread-prone tree species.<br />
• Establishment of a dense vegetation cover.<br />
This could be another woody crop (usually forest) or it might be a vigorous herbaceous<br />
cover.<br />
~ Woody crop – usually forest. Most of the invasive conifers are too light<br />
demanding to be able to establish from seed under a closed canopy woody cover,<br />
especially if it is tall, such as a forest. Hence, one wilding prevention option for Pukaki<br />
Downs is to establish susceptible land in a new forest cover. If the area to be planted is<br />
one from which seed could be disseminated elsewhere, then a non or less spread-prone<br />
species should be chosen. This might be ponderosa or radiata pine, or a radiata x<br />
Knobcone pine (P. attenuata) hybrid on the harsher sites, or perhaps a cypress<br />
(Cupressus species, such as Leyland or Lawsons cypress) on the more benign sites,<br />
depending on the objective of the planting (timber production or carbon storage). Where<br />
the risk of spread off-site is less, then a more valuable species such as Douglas-fir could<br />
be planted.<br />
10
~ Herbaceous cover. Wildings have difficulty establishing within a vigorous<br />
herbaceous cover. This has been demonstrated over on Mt Cook station, where no<br />
wildings can be found in the dense grass / clover cover which established quickly after a<br />
fire destroyed a large area of a wilding Corsican pine forest. Where trees are felled, and<br />
the resulting slash is not so thick as to prevent any light reaching the ground surface,<br />
herbaceous growth, particularly of grasses, can be sufficiently vigorous to prevent wilding<br />
re-establishment from seed for a number of years (see above). Evidence of this can be<br />
seen at a number of sites on Pukaki Downs.<br />
• Maintaining improved pasture and intensive grazing.<br />
Pasture which is improved <strong>by</strong> seeding and fertilising will not be invaded <strong>by</strong> wildings. This<br />
is well shown on the Canterbury plains, despite the presence of a wide range of spreadprone<br />
conifers. There is also good evidence on Pukaki Downs, where the hay paddocks in<br />
block 31 and parts of block 25 are free of wildings despite the fact that there are forests of<br />
contorta pine adjacent. Although improved pasture will prevent wilding invasion, it is<br />
acknowledged that much of Pukaki Downs does not lend itself to this form of wilding<br />
prevention. Also, it must be remembered that a) this improvement and the grazing which<br />
it can support must be maintained, and b) if the seed rain from immediately adjacent trees<br />
is high, then even a relatively small easing of grazing and/or fertiliser regimes can result in<br />
wildings getting established. In addition to improved pasture, the cropping of land for<br />
arable purposes will deliver the same wilding prevention outcome.<br />
• Planting a margin of less spread-prone trees.<br />
The theory here is that in a forest, most cones are produced on edge trees which have<br />
green crowns extending to ground level - as opposed to the smaller and higher canopies<br />
of internal trees. In addition, edge trees are more likely to disseminate seed onto<br />
unplanted adjacent land. Therefore, if the margin of a forest is planted with a zero or less<br />
spread-prone species, the risk of wilding spread is reduced. If the marginal species is<br />
faster growing than the forest species, then it can also create a greater physical barrier to<br />
the spread of seed. However, this marginal planting can only be most effective on flat<br />
land. Where the forest is on rolling or hilly land, especially if this faces into the prevailing<br />
wind, then there are greater opportunities for seed to be picked up from the internal tree<br />
canopy and the effectiveness of marginal planting is diminished.<br />
Assisting containment on Pukaki Downs.<br />
Taking the above points in mind, the best containment management options appear to be<br />
the:<br />
~ Establishment of forests of less spread-prone species, such as the radiata x<br />
attenuata hybrid, on areas immediately to the west of the contorta forests most likely to<br />
remain intact – such as on blocks 12, 13, 19 and the western parts of block 9. In a<br />
continuation of this western edge planting to the north of the property, further<br />
establishment could be made on the eastern slopes under the Little Rhoboro Hills (blocks<br />
20 and 14) - and also along the northern boundary with Ferintosh, down to SH80. Over<br />
time, the 20m strip of less spread-prone species could be extended down the northeastern<br />
margin alongside SH80, there<strong>by</strong> minimising the spread of wildings onto the<br />
highway margin. Such a strip could be established wherever spread-prone trees are likely<br />
to grow alongside SH80. As they would be on the western side of the road, there should<br />
be no risk of promoting highway icing during the winter.<br />
To the east of SH80 in block 32, improved pastures and grazing are restricting fringe<br />
spread westwards from the lakeside forests of contorta pine – and also from smaller<br />
planted areas of Corsican pine and Douglas-fir. Additional forests, or a 4-row strip, of less<br />
spread-prone species could be established along the western margin of these more<br />
spread-prone species, in order to further reduce the risk of unwanted spread.<br />
~ Maintenance of improved pasture and associated grazing (or arable cropping)<br />
where it is currently restricting wilding establishment. This is in blocks 31 (especially<br />
around the Dusky Reserve) and 32 and further to the west in the southern half of block 25,<br />
just beyond the forested blocks 9 and 12. The hilly topography, limited moisture<br />
11
availability and poor soil quality on much of the rest of Pukaki Downs limits the use of<br />
improved pasture and arable cropping - unless irrigation is introduced. Fertilising would<br />
enhance any grass regrowth amongst felled trees (even though no grazing would be<br />
associated) and further diminish opportunities for wilding invasion.<br />
~ Planting of a margin of less spread-prone trees. In effect, this is what is being<br />
implemented <strong>by</strong> the containment forest planting recommended immediately above. It is<br />
recommended that the felled strips <strong>by</strong> the northern boundary with Ferintosh and in the<br />
forested areas alongside SH80 be made ‘wilding-proof’ <strong>by</strong> either fertilising to promote<br />
vigorous herbaceous growth or planting of less spread-prone species. Even though the<br />
main spread of conifer seed is from north to south, a marginal strip of trees along the<br />
southern fence-line with Rhoboro Downs station is less important, due to there either<br />
being dense forest on both sides of the boundary (the eastern half) or no trees present at<br />
all (the western half). Apart from the outer boundaries, all the fenced margins between<br />
remaining contorta pine forests and the tree-less pasture areas within the station could be<br />
planted in four rows of radiata, its hybrids or ponderosa pine – around the northern and<br />
western margins of block 31 and around the western margins of blocks 9, 12, 13 and 19.<br />
If this were to be carried out, the latter four blocks would be the priority as, although the<br />
topography on the forested side of the fence is more varied (greater risk of seed being<br />
blown from the forest canopy), the grazing pressure is generally lighter (and hence the<br />
spread risk higher) on that side of the property. Prior to any marginal strip planting, any<br />
existing contorta pine trees would have to be removed from along the fencelines. The<br />
need for this marginal 4-row planting would, of course, be negated if the contorta forests<br />
were replaced with a less spread-prone species.<br />
Areas for C storage management<br />
Described above are the areas recommended for wilding removal, those where less<br />
spread-prone species could be planted and those where the maintenance of current<br />
pasture and arable management will restrict wilding establishment. The remainder of<br />
Pukaki Downs could be managed for carbon storage. This ties in closely with the pink<br />
and pink-striped portions shown on the map (see ‘containment area’ above). Initially, the<br />
dominant species would be contorta pine, but over time it may be possible to replace<br />
these with the less spread-prone species.<br />
Discussion<br />
As there is a major tourist road (SH80) running through the property, the wilding<br />
conifer problem along the south-western shores of Lake Pukaki is well known.<br />
Unfortunately, it involves the most spread-prone conifer species, contorta pine. Although<br />
other species such as Douglas-fir, Corsican pine and larch are also involved, if contorta<br />
pine was not present, then there would be no need for this report. Wildings have been<br />
spreading since the 1960s, but the area obviously affected has only increased significantly<br />
in the last 15 years. This has been largely triggered <strong>by</strong> spread from the lake-shore<br />
plantings carried out after the lake was raised in the early 1970s - although most of the<br />
contorta forests in the south-eastern portion of Pukaki Downs originate from trees present<br />
before that time. The patterns of spread likely in the future are well indicated <strong>by</strong> the<br />
pattern of spread over the last few decades. These show that spread is mainly to the<br />
south, driven <strong>by</strong> the prevailing strong northerly winds, but that occasionally a more<br />
easterly wind can pick up and carry seed high into the air and far to the south-east. This<br />
is what appears to have happened back in the early 1990s, resulting in a scattering of<br />
wide-spread outlier trees in the upper Twizel river valley. Unfortunately, these outliers<br />
were allowed to mature and cone well before they were removed in the mid 2000s, giving<br />
rise to the islands of fringe spread so obvious today. The ‘one-off’ nature of this spread<br />
12
event indicates that once the Twizel river flats are cleared, they should not be re-invaded<br />
often and hence should not be too difficult to keep clear in the future – as long as any<br />
wilding trees which do establish are removed before age 5-6, when they begin coning.<br />
This ‘stitch-in-time-saves-nine’ maxim must always be kept foremost in any management<br />
planning. Importantly, the incidence of re-invasion and need for timely removal should be<br />
diminished <strong>by</strong> the control and containment management options outlined above.<br />
Apart from removing wildings, particularly outlier trees, before they cone, the other<br />
major aspect of wilding control which should never be forgotten is the need for long-term<br />
commitment. Even if a first removal sweep can be carried out in good time, there will be<br />
some delayed germination of seed in the soil (although little takes places after 4 years)<br />
plus small seedlings will be missed. A second sweep is therefore needed within 4 years<br />
of the first removal (for contorta pine), and there is usually a need for a third sweep 4<br />
years later to remove the last wildings. This sequence is needed if there is no other local<br />
seed source, which unfortunately there will be at Pukaki Downs due to the present<br />
strategy involving containment, not eradication. Therefore, if wildings are not to affect<br />
more land in and around Pukaki Downs, removal sweeps outside the containment area<br />
will be needed at least every 4 years for as long as seeding contorta pine trees remain in<br />
the locality.<br />
Within the containment area, the conifer forests could be managed, although<br />
contorta pine is not a favoured production species in <strong>New</strong> <strong>Zealand</strong>, and there is currently<br />
no ready market for timber or fibre. Such prospects are not improved <strong>by</strong> the forests being<br />
‘wild’ and having had no previous management – leading to considerable stand variation<br />
within the forest. The other obvious management option is to target carbon credits via the<br />
Emissions Trading Scheme (ETS). Although this author is not in favour of wilding-risk<br />
species (such as contorta) being managed for carbon gain, especially in high spread-risk<br />
environments, the financial gains from such management on the areas with lower spreadrisk<br />
could be used for control of wildings on the higher risk areas. If forest management is<br />
a long-term aim (as opposed to conifer eradication), then even better would be the<br />
gradual replacement of contorta pine in the containment area with a less spread-prone<br />
species. Such replacement would eventually suppress the resident contorta pine, but<br />
significant inputs would be required to ensure that the replacement species prevailed over<br />
the naturally regenerating and vigorous contorta pine wildings.<br />
Local community wilding control group. Recently, led <strong>by</strong> occupants of Pukaki<br />
Downs, local land owners affected <strong>by</strong> wilding spread have got together to form the Lake<br />
Pukaki Wilding Tree Management Trust. There are six other similar groups operating<br />
within <strong>New</strong> <strong>Zealand</strong>, and they have shown how collaborative action can make a huge<br />
difference to fund-raising opportunities and the mounting of large-scale and cost-effective<br />
wilding removal operations. Unfortunately, not all affected landowners around Lake<br />
Pukaki are members of the present Trust and this will affect the success of their<br />
management, as wildings have no respect for property boundaries. In addition, the L.<br />
Pukaki Trust is the only group to be proposing containment as an integral part of their<br />
management – all the others have targeted elimination of both wildings and the seed<br />
source trees. All the same, the formation of the Trust does give formal recognition to the<br />
seriousness of the wilding spread in the area, and sets the foundation for a worthwhile<br />
long-term control programme.<br />
This author wishes them all the very best in their endeavours.<br />
Recommendations<br />
On Pukaki Downs it is recommended that:<br />
• All wildings be removed in the near future from the upper Twizel river<br />
catchment (blocks 25-29), except in the most densely forested areas<br />
in the eastern margin of that area (blocks 9-13 plus 19).<br />
13
• All wildings should also be removed from block 29, although planting it<br />
with a less spread-prone species is an option.<br />
• All wildings be removed from the steep slopes of the Rhoboro Range<br />
in the most north-western part of the station (block 30).<br />
• All wildings be removed in a 20m strip along the northern boundary<br />
with Ferintosh station and in a similar strip alongside SH80.<br />
• If finances allow (last priority) all wildings be removed from the steeper<br />
eastern scarp slopes (northern portion) of the Little Rhoboro Hills<br />
(block 20 and steeper part of 14).<br />
• Improved pasture and associated grazing (and/or arable cropping) be<br />
maintained where it is currently stopping wilding establishment -<br />
blocks 31 and 32 (both sides of SH80) and further to the west in parts<br />
of block 25). The north-eastern margin of block 31 would run out from<br />
the northern margin of DOC’s Dusky Reserve in order to maintain a<br />
treeless pasture margin.<br />
• Replacement plantings of less spread-prone species, such as radiata<br />
pine, its hybrid with Knobcone pine (P.radiata x P. attenuata) or<br />
ponderosa pine, be carried out along the eastern margins of the<br />
cleared areas in the upper Twizel river valley, either as 4-row marginal<br />
plantings along the western edges of blocks 9, 12, 13 and 19 (if<br />
retained in contorta pine), or as whole block replacement.<br />
• Replacement plantings of less spread-prone species, such as radiata<br />
pine, its hybrid with Knobcone pine (P.radiata x P. attenuata) or<br />
ponderosa pine (minimum of 4 rows), could also be carried out along<br />
the western margins of the lakeshore contorta pine forests in the<br />
south-eastern part of block 32. This will not be necessary where<br />
ponderosa or Corsican pine make up the current margin, or where<br />
adjacent pasture cover and grazing pressure is sufficient to stop<br />
significant establishment of wildings.<br />
• Replacement plantings or fertilising be carried out in the 20m marginal<br />
strips along the Ferintosh boundary (top of blocks 16 and 24) and<br />
alongside SH80.<br />
• Marginal strips (4 rows wide) be planted along the fenced north and<br />
western margins of the tree-less pasture-dominated block 31.<br />
• Blocks 9-24 (the pink and pink-striped areas on the map), including<br />
the corridor north of the Dusky Reserve between blocks 21 / 16 and<br />
17 / 22 – 23, will become the containment area and could be managed<br />
for carbon storage. Initially, the dominant species would be contorta<br />
pine, but over time the aim should be to replace these with less<br />
spread-prone species.<br />
• Wilding removal sweeps be carried out before coning age (no more<br />
than 4 years apart) on all cleared or otherwise tree-less areas.<br />
• Long-term planning be initiated to ensure that the above to be<br />
implemented.<br />
Acknowledgement<br />
The author is most grateful to the residents of Pukaki Downs, especially <strong>Blake</strong> <strong>Foster</strong>, for<br />
their support during the field-work and the writing of this report.<br />
14
Above. The clear corridor (pink-striped on map) in the north-eastern part of Pukaki<br />
Downs, between blocks 21 / 16 and 17/ 22-23). This will be very hard to maintain free<br />
of wildings, so unless the contorta forest alongside is replaced with a less spread-prone<br />
species, it should become part of the forested containment area.<br />
Below. Felled 50+ year old contorta trees <strong>by</strong> the musterer’s hut in block 26. These<br />
would have given rise to much of the dense wilding cover immediately to the south.<br />
15
Above (2008) and below (2010) - outlier wildings in the upper Twizel river catchment. Their uniform age indicates<br />
that they arrived at the same time in the early 1990s, and that such a distant spread event does not happen often.<br />
Unfortunately, they were allowed to cone before removal, resulting in islands of fringe spread (obvious in bottom photo).<br />
All fringe spread has been to the south of parent trees, indicating the prevailing north wind (right to left in photos). If<br />
removed before coning, it should not be onerous to keep this site free of wildings – as invasion is infrequent.<br />
Left – Twizel river flats (2010). An ‘island’ of<br />
young wildings, parented <strong>by</strong> a lone outlier wilding<br />
parent tree, which was felled a few years<br />
previously (being held up in photo). If this tree had<br />
been felled before age 5, no wildings would be<br />
present. Its progeny are now aged 5-6 and just<br />
starting to cone. If left intact and allowed to<br />
disseminate seed, wilding removal costs will be<br />
increased significantly. Hence the wilding control<br />
motto of “Stitch in time saves nine”<br />
Left (2009). Looking<br />
south from Little<br />
Rhoboro Hills ridge.<br />
Contorta pine is rapidly<br />
becoming dominant,<br />
except in middle distant<br />
left where improved<br />
pasture is preventing<br />
invasion. Containment<br />
(and possibly forest<br />
management) is the<br />
cheapest option for this<br />
area, where seed sources<br />
may remain upwind.<br />
16
Developments from Rural Delivery website for program on wilding control at Pukaki Downs<br />
Wilding Pine Control<br />
October 8, 2011<br />
Pukaki Downs are using the carbon credits from a core area of wilding pines now in the<br />
Emissions Trading Scheme to fund wilding control over the rest of their property.<br />
After Lake Pukaki was raised for the second time – <strong>by</strong> 37m in the 1970’s – there were areas of<br />
wilding conifers along the lake front shore, indicating this spread had come from plantings<br />
around the now submerged early homesteads.<br />
Over 10,000 mixed pine species, including Pinus contorta, were planted on the lake front of Lake<br />
Pukaki in the 1970’s for erosion control <strong>by</strong> the Ministry of Works.<br />
It’s a very good climate for growing trees. This species is most prone to spreading, and they<br />
have, and they are very costly to control. And until now there’s been no money floating around<br />
to help landowners with pine control.<br />
The rest of the farm is used for grazing sheep and cattle, organic grain cropping and organic<br />
lavender production. Eco-tourism and other forestry ventures are being developed.<br />
<strong>Blake</strong> is also treasurer of the Lake Pukaki Wilding Tree and Management Trust that has been<br />
formed <strong>by</strong> a number of station holders in the area to try and get funding for wilding control.<br />
Pukaki Downs has a huge problem with wilding pines on its property but the problem has only<br />
increased in the last 15 years.<br />
By the middle of last year, wilding Pinus contorta had spread so much that it covered 30 or 40%<br />
of the property and had turned into a forest.<br />
Much of the remaining area has widely scattered outlier trees and if left unmanaged, wildings<br />
would dominate the majority of the property.<br />
It’s a very visual weed in an area with high landscape values, and the major tourist route of Mt<br />
Cook Road runs through the property for about 8km.<br />
The spread is mainly from the lakeshore plantings, and the seed has been blown <strong>by</strong> strong<br />
northerly winds.<br />
When the owners were looking at ways they could self-fund wilding conifer control, the ETS<br />
was coming into play.
We talked with MAF people in Wellington who said the wilding pines fitted the definition of a<br />
forest under the ETS, and could be entered into the scheme.<br />
The ETS seemed to be a self-funding way to deal with the situation, and provide an income<br />
stream for us to contain it, including planting a tree buffer zone and chip away at the forest area<br />
over a number of years, replacing it with a different species.<br />
The whole idea is to get rid of the wildings, so we drew a line in the sand surrounding a core area<br />
of trees, and put that area into the ETS.<br />
We use the funds from the sale of carbon credits to clear all the outliers around it.<br />
We are planting 40,000 non-spreading trees around the core area to act as a buffer. These trees<br />
will gradually form an effective natural barrier to prevent the airborne spread of wild conifer<br />
seed.<br />
Gradually we also plan to replace the core wilding area with a hybrid species, a cross between<br />
Pinus radiata and P. attenuata, (knobcone pine) which is less prone to spreading. That’s because<br />
the knobcone pine’s cones only open as a result of fire, and radiata pine is a low-spread risk for<br />
us.<br />
Our core ETS area is 1100ha, which is approximately a quarter of the property. The remainder of<br />
the property has wildings spread across it.<br />
Last year we made huge inroads, clearing 500ha. You have to get them while they are young and<br />
haven’t produced cones, which is after about five years.<br />
After receiving our first round of carbon credits and selling some of them, we then knew we had<br />
the funds to be proactive with the problem.<br />
We were fortunate to be able to obtain help from Nick Ledgard of Scion to do a detailed report<br />
which identified where the spread was coming from, where we should start control from and<br />
what the high and low risk areas were.<br />
That’s how we came to put the low spread risk area into the carbon sink.<br />
We have followed his recommendations.<br />
This way we have a self-funding project, and last year we employed a gang of nine for five<br />
weeks who used scrub bars. We had another crew of four. And we have purchased a mechanical<br />
slasher at a cost of $150,000 to slash small trees.<br />
The control work costs us $15,000 a week, and it is going well. It’s pretty hard work for the<br />
team.<br />
We also clear the road frontage back to the forest edge in areas that are clear of trees.
We have sold the carbon credits through a broker/consultant. For each of the commitment<br />
periods you get an allotment of carbon credits. You don’t have to sell them; you can keep them.<br />
But for us selling them pays for the control work on the rest of the area.<br />
The core area doesn’t have a lot of commercial value, and it has never had any silviculture. It’s<br />
quite a long way from the market unless there is a major market change.<br />
We have been looking at making wood pellets and firewood out of them; we’re just investigating<br />
that at the moment.<br />
We are trying to use the funds responsibly, not just put the wildings in the ETS, take the money<br />
and run.<br />
While we are using the funds to eradicate the trees, we feared others might not use the funds<br />
from the sale of carbon credits for eradicating wildings.<br />
Our central aim is to get rid of the contorta species.<br />
We’ve had huge success in the last year and the ETS has provided a way for it to happen.<br />
I would say we are looking at control for another 15 years at least.<br />
Wilding forests are called Tree Weed Forests under the ETS.<br />
<strong>Blake</strong> has lobbied MAF and ECAN to give an alternative view on how to get funding from the<br />
ETS to deal with the problem of wilding trees. This view of using the ETS funds to deal with<br />
clearing wildings can be seen as partnering with ECAN. And the submission was received<br />
favourably with ECAN amending one of its rules. The theme of the submissions were to:<br />
• use a certain percentage of the income derived from ETS Carbon Credits to be put back into<br />
controlling the spread ;<br />
• set the area of the tree weed forest to be the area placed in the ETS and not allow it to expand<br />
beyond this area ;<br />
• use income from ETS, plant buffer zones of non spreading species to contain seed spread ;<br />
• replant the existing forest into a non spreading species over time and enter this new forest of<br />
non spreading trees into the ETS to further fund the programme ;<br />
• use the money from ETS to fund the long term eradication of wildings outside the containment<br />
area;
• use income from ETS to pay for mulching machines and scrub bar gangs to make buffer zones<br />
and to eradicate juvenile wilding conifers as they grow among the planting of non spreading<br />
species.<br />
<strong>Blake</strong>’s conclusion to his MAF submission stated:<br />
“<strong>New</strong>, non-traditional approaches to containment and eradication of pest species should be<br />
allowed.<br />
For example with wilding pines, changing from a standard policy of informal<br />
forest management with a focus on eradication, to a new policy of structured forest monitoring<br />
and replacement of existing wilding species with non-wilding ones.”<br />
He wanted a move from a short-term focus on eradication of wilding conifers to a longer-term,<br />
progressive series of steps that include initial containment, managed harvesting and replacement<br />
of wilding species <strong>by</strong> non-wilding ones over decades.<br />
“If this process is extended over a longer timeline there may be better chance of long-term<br />
success plus the project might become self-funding if revenue from environmental services such<br />
as carbon sequestration or commercial timber production was integrated into the management<br />
plan.<br />
The management at Pukaki Downs has spent considerable, time, energy, money and resources<br />
over the years in consultation with other landowners, foresters, scientists, DoC consultants,<br />
practical working people and independent business people who specialise in tree and forestry<br />
management.<br />
Through this process we have arrived at the conclusion that eradication of all wilding trees is an<br />
unreal goal. We have seen first hand that in the face of this unattainable outcome many people<br />
with a wilding pest problem simply stop trying to beat the odds and give up.<br />
The biggest obstacle to wilding pine containment is an economic one. The enormity of the<br />
problem,(which in most cases in the Twizel area was an inherited one, either from original<br />
plantings from Lands and Surveys operations or from wind blown seed scattering), has reduced<br />
landowners to despondency.<br />
Millions of dollars are required to create change and landowners are well aware of their lack of<br />
ability to effect such change. We have reached the conclusion of creating buffer zones around<br />
existing wilding forests with fast growing, non-spreading tree species, while maintaining and<br />
managing any new growth.”