One Tree Hill summit project
New tree planting proposal
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2.0 Considerations
2.3 Site assessment
2.3.1 Historical and cultural context
One Tree (Maungakiekie) is the largest but not quite the tallest volcanic cone in the Auckland region. The summit is 182m above sea level. Mt Eden (Maungawhau)
is about another 13m higher. One Tree Hill however, remains largely undamaged by urban development; even the lower slopes are preserved in extensive parklands
(One Tree Hill Domain and Cornwall Park). The hill has a strong history of inhabitation by successive Maori peoples who lived on it from about 1400AD until 1822.
The hill or maunga, was the site of a massive fortified Pa surrounded by cultivated land and housing on the lower slopes. The site is one of Auckland’s most
significant archaeological sites. The highest point of the summit has been crowned by a tree and more recently the obelisk and grave of Sir Logan Campbell.
The recently lost lone Pine had a predecessor that was of spiritual and cultural significance to local Maori. While the exact history of that tree is still
discussed, it is generally agreed that the tree was a totara and was planted in about 1600 AD as a seedling according to Maori custom upon the umbilical cord of a
child of high rank. The child (Koroki) was the son of a Ngati Awa chief who was born while his mother was visiting the Pa. So it is considered that it was because
of the great Koroki's "mana" that the little tree grew and flourished, even on this windswept summit.
History has it that many years later (1852); a European workman tragically destroyed the tree in a fit of anger after he reached the top because an expected
parcel of meat had failed to arrive. (Reference: "In the Shadow of Maungakiekie" A history of One Tree Hill and its Environs from Pre-Maori times to 1989,
Commissioned by the One Tree Hill Borough Council).
There have been attempts to establish another totara on the site but these have failed. However, pine trees planted originally as a shelter belt did survive and
over time through attrition, there remained one lone pine which stood on the summit until October last year. The site and tree therefore together enshrine a
significant part of Auckland’s history and both are revered by Maori and European settlers alike.
The removal of the original totara has continued to be a source of great pain to local Maori and the opportunity now exists to put right the wrongs of the past
by recognising the importance of both the site and the symbolism in the proposed new planting.
Through key stakeholder consultation the Council has sought to obtain a clearer understanding of all the issues that surround this land and tree and from that
have formulated the proposal set out in this report.
A resource consent under the Resource Management Act (1991) is a requirement of planting on this historic site because of the archaeological significance of
the site itself as well as the presence of Sir John Logan Campbell’s grave and the obelisk. This proposal is to plant a new tree. The Council concedes that it is
not possible to mitigate the loss of the former lone pine. However, this proposal provides the opportunity to make up for the mis- understanding and mistakes of
the past so all Aucklanders can appreciate the full significance of this maunga.
The underlying pretext to the planting proposal is that the ultimate outcome will be one tree of landscape quality to obtain visual significance equating to the
former lone pine. Additionally, the tree and planting should reflect cultural values in recognition of the special significance this site has to Maori as well as
the sharing of cultural understanding between Maori and other sectors of the community. The objective is to share in the significance of the planting spiritually
and culturally for the benefit of all people of Tamaki-makaurau.
2.3.2 Landscape
The silhouette of lone pine tree atop the distinctive volcanic landform of One Tree Hill (Maungakiekie), counter balanced by the built form of the obelisk, has
made One Tree Hill a landmark in Auckland City. The volcanic cone, the obelisk, and the summit tree collectively exhibited contrasting form and character, and
created a unique and immediately recognisable symbol of Auckland. With the pine gone, there is a perception of an imbalance between the natural and built form of
the maunga.
While it may seem urgent to achieve a replacement, which strongly replicates the previous composition (of lone pine and obelisk), there is no doubt that this
will become less important over time. Now that the last remaining pine tree is gone, and during the establishment of a new tree (20–30 years and possibly up to 50
years to attain maturity), an acceptance of the new tree is expected to build. Therefore, time is expected to reduce the significance of the comparison between
the previous tree and its replacement.
Until a replacement tree gains sufficient size to achieve a distant visual impact, the appearance of One Tree Hill will be altered. It is unlikely that the
vegetative element of the One Tree Hill composition will be visually significant for at least 50 years or more.
Also, the planting of a new tree will not replicate the familiar form of the previous summit tree. The previous tree developed its growth habit as a result of
its species characteristics and its position at the edge of the original group of at least five pine trees.
It is therefore important to appreciate that the previous pine tree and its unique landscape value, as an icon is irreplaceable. There is no mitigation in
terms of tree planting that will replace this value. Therefore, it is a commitment to the symbolism and the intrinsic value of a singular specimen tree in
relation to its site and environment that should be considered.
Also, the factor of time cannot be discounted from the evolution of landscape. The historical context of the relationship between a tree or trees and the
summit of One Tree Hill (Maungakiekie) underpins any planting that is undertaken today. This must reflect the past, present and future and recognise that a
biological being such as a tree has its own life span beyond a human generation.
2.3.3 Arboricultural
The site is considered to be extremely difficult for the establishment of a tree, and several past attempts to plant trees on the summit have failed. There is
no existing protection from wind and sun, and free draining soil results in dry conditions.
Water requirements
Due to the exposed nature of the site (altitude, local topography and lack of sheltering vegetation) and the nature of free draining volcanic soil, the
evapo-transpiration rates and subsequent water requirements of the new tree are expected to be high.
Rainfall is spread relatively evenly throughout the year, with the highest rainfall during June, July, and August. However, the site can become extremely dry
during summer months, and the period in which trees in Auckland can become stressed through lack of water is from October until April.
Generally the period of water stress is in a young tree’s establishment phase and is seasonal. However, under these site conditions this period is highly
likely to be prolonged. Therefore, it is critical that the tree species, and its size at time of planting, can naturally tolerate and adapt to these conditions.
Soil conditions
The average existing depth of soil is estimated to be 0.66 metres, calculated on an average of ten readings taken within the proposed planting site. The soil is
free draining, and is comprised of weathered scoria and organic humus. Basalt scoria is expected to underlie this.
The planting site has a slight to medium acidic soil pH of 5.97, calculated on an average of ten readings. This pH level is suitable for all of the proposed
replacement species.
The backfill soil that is used at the time of planting should be of a similar type, texture, and pH to the existing soil. This will ensure that the interface
between the two soil mediums is compatible, to promote root growth and tree establishment.
This soil will be readily available from within the grounds of One Tree Hill Domain or Cornwall Park, and some soil could also be imported by respective iwi
as a ceremonial gesture at the time of planting.
The excavation and reinstatement process will ensure that most of the planting medium is adequately aerated for optimal tree establishment and growth. In areas
where excavation and reinstatement has not taken place it will be necessary to improve the aeration of the existing soil by manual means, such as the use of hand
forks.
Stump grinding
Resource Consent has been granted for the removal of the previous pine stump. Stump grinding will enable further investigation into the ground conditions and will
give a more definitive picture of the available space and soil conditions for planting.
2.3.4 Archaeological considerations
Maungakiekie is a site of prime archaeological and geological importance, and the site is scheduled in the Auckland City District Plan on both counts.
Ground disturbance is not to occur without an archaeologist present to supervise the works for site protection and to record any archaeological features that
may be discovered.
Initial investigations
The limits of excavation have been defined by the consultant archaeologist as the stump and the main buttress roots of the previous tree. This area is measured
from the centre of the previous tree (stump), and is approximately 6 metres in diameter (3m radius) and up to one metre deep.
The area available for the replacement planting is restricted to the area immediately surrounding the previous tree. Therefore, the previous tree required removal
prior to replacement planting. The location, size, and number of trees planted will also be limited by the space available.
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| Figure 1: Area of proposed excavation |
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Depth of soil on site, the
presence of rock and/or archaeological remains, and the size of the replacement
tree (or trees) will determine the depth of excavations. It is expected that
excavations of one metre deep will not be required for most of the defined area
if small grade trees are planted. The photograph (see Figure 1) shows a string
line around the base of the tree, indicating the approximate area to which the
proposed excavation is limited.
Historic Places Trust response
Initial feedback from
the New Zealand Historic Places Trust to the proposal to plant a new summit tree
included the following:
- the tree should be located
in the area already disturbed by the stump removal
- consideration should be
given to the potential root growth of the species. A species with a
confined and limited root growth is far more acceptable than one with an
extensive root system (from an archaeological point of view)
- the new tree should not
have a root system that will impact on the ground outside the area
already disturbed by the root system of the pine and the stump removal
- at no time is it
acceptable for a crane or heavy equipment to be placed on archaeological
features with or without protective matting. The crane and heavy
equipment must be located on the sealed carpark area or on the summit
road.
Root system development
Photographs from 1907
show five mature pine trees on the summit. Three of the stumps remain on the
western side of the previous tree (see Figure 2). All of the proposed
replacement species have the potential to develop a root system of a similar
size to the root system of the previous tree.
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Figure
2: Root system of existing
tree and
stump remnants of other pines
(photograph taken in 1993) |
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The root growth of individual
trees is variable, and it is difficult to determine whether a new tree will have
a more extensive root system than the previous tree. However, it is highly
unlikely that the root system of a single tree will exceed the root mass of the
pine trees that were planted in the 1870’s. In the event of a multiple tree
planting, with the ultimate objective of preserving a single specimen, perimeter
trees would not attain maturity and it is likely that the dominant tree would
occupy the site of the previous pine. It is therefore considered that root
growth would not exceed that which has already affected the site.
Authority to modify an
archaeological site
On 1 September 2000 the
New Zealand Historic Places Trust granted a general (in whole) authority to
modify, with conditions, the archaeological site known as Maungakiekie/One Tree
Hill (site record No:R11/14) in accordance with section 14 (1) of the Historic
Places Act (1993) for the purposes of tree removal and replacement. This
authority to modify is valid for a two-year period, which would allow for
planting up to the end of August 2002 without further application.
2.3.5 Engineering considerations
Due to the
archaeological importance and topography of the site, there are constraints
regarding the maximum size tree that can be planted. This is because of the
difficulty, and hence great care needed, with site access and lifting capacities
of machinery.
Options have been
investigated regarding transporting and lifting a semi-mature tree (weighing up
to 5.0 tonne) onto the site – as calculated at maximum safe working load from
closest access at approximately 22m from the centre of previous pine stump –
see engineering drawings (Appendix1)
An 80 tonne crane (this
describes maximum lift capacity) is capable of this whereas this would not be
feasible for a smaller crane or largest available helicopter.
A semi-mature 5.0 tonne
tree is expected to be 5.5 to 7.0 metres in height when planted (depending upon
the tree species). The transplanting of a semi-mature tree would extend
excavation for preparation and planting (significantly more than the planting of
a small tree or trees) and increase potential for disturbance beyond the
planting site.
A crane could only be
used on sealed surfaces and heavy machinery would be required on the summit road
and car park areas. For site protection suitable ballast would be needed to
protect ground surfaces from being damaged by crane outriggers. All wheels of an
80 tonne crane pivot to minimise turning circle requirements and road surface
scuffing damage. This crane weighs 45 tonne when in transit and 57 tonne when
set up on site, and is not expected to cause damage to archaeological and
geological features, including the structural integrity of the carriageway.
An 80 tonne crane
was successfully used as part of the pine tree and stone plinth removal
operation in October 2000.
