One Tree Hill summit project

New tree planting proposal

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Appendix B

Potential effects on the site

Single semi-mature transplant

Small grade multiple planting

Positive attributes

Heavy machinery will not be required on site to assist with planting.

Small grade trees can be planted by hand.

Negative attributes

Heavy machinery will be required on site to transport and lift the tree into position for planting.

The depth of excavation necessary for transplanting a 5.0 tonne tree is expected to be 0.8 to 0.9 metres, and excavations into rock may be required to accommodate the root ball.

The need for a support system below ground may impact on archaeological values, due to excavation requirements.

This option utilises the entire designated planting zone, and incorporates the grinding of all surface roots and the movement of soil and stump grinding materials on and off site.

Environmental and establishment issues

Single semi-mature transplant

Small grade multiple planting

Positive attributes

A semi-mature tree planted on the summit of Maungakiekie will have greater presence, and may be perceived to be less vulnerable to physical damage.

The most natural form of shelter can be achieved by group planting, and trees planted using this option are most likely to mutually adapt to the site conditions.

Results from research show that vigorous growth returns to small grade trees sooner after planting.

Artificial shelter may not be required.

Small grade trees could be supported using 1.5 metre long stakes within the area available for excavation.

Environmental and establishment issues

Single semi-mature transplant

Small grade multiple planting

Negative attributes

Semi-mature transplants have high risk of establishment failure and significant after-care maintenance requirements, especially on an exposed site. This is due to large transplants being less vigorous and losing a greater ratio of root mass during transplanting.

A semi-mature transplant is expected to require much greater quantities of irrigation than a smaller tree (or trees).

Artificial shelter will be required to assist establishment and survival on the exposed site. Artificial fabric shelter may not be desirable on visual grounds, is likely to provide protection to the lower parts of the tree only, and may not be effective because of this.

The most effective support is likely to be installed below ground to hold the root-ball in place.

Alternatively the tree could be mound planted by raising soil levels around the root-ball by 250 to 300 mm. However, mound planting could increase evapo-transpiration rates and the likelihood of post-planting shock because of the root-ball being exposed.

This option creates issues regarding appropriate group management over time, including the removal of the shelter trees and the selection of the tree that will ultimately be the replacement.

It is likely that a new cage would be installed to protect the tree from damage.

Growth rates and tree form	Single semi-mature transplant	Small grade multiple planting
Tree size when planted	The following sizes are estimated for a 5.0 tonne tree of each species. Totara: 6.0 to 7.0 metres high and 4.0 to 5.0 metres wide. Pohutukawa: 5.5 to 6.0 metres high and 4.0 to 5.0 metres wide.	At the time of planting it is expected that the small grade trees will be the following sizes. Totara: 1.3 metres high Pohutukawa: 1.0 metre high.
Growth over 50 years	Totara: expected to increase in height by 0.5 metres over fifty years to be 6.5 to 7.5 metres high. Pohutukawa: expected to increase in height by 2.0 metres over fifty years to be 7.5 to 8.0 metres high.	Totara: expected to increase in height by 7.7 metres over fifty years to be 9.0 metres high. Pohutukawa: expected to increase in height by 7.5 metres over fifty years to be 8.5 metres high.
Positive growth attributes	The benefit of using a semi-mature transplant to replace the existing tree is the immediate visual impact when planted.	Young trees are expected to be more vigorous long term than semi-mature trees. The growth characteristics of trees in a group are likely to be upright, resembling the growth habit of the previous tree, regardless of species.
Negative growth attributes	The growth habit of either species will depend greatly upon tree form at the time of transplanting. There are fewer opportunities for selection of best form trees when acquiring a tree for transplanting.	It is expected that suitable grade trees will take three to four years to propagate and grow.