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March, 2018

Assessing the feasibility of a continuous cover forestry system for radiata pine in small-scale forests

Wellington and Wairarapa Branches of the NZ Farm Forestry Association have received a Sustainable Farming Fund grant for a feasibility study to evaluate the potential for a continuous cover forestry system in small-scale radiata pine plantations. Harriet Palmer, project leader, outlines the project and what it ams to achieve:

The problem/opportunity

New Zealand plantation forestry is characterised by single-species, even-age stands managed on clear-fell regimes. In contrast, in other parts of the world, continuous cover forestry (CCF) regimes are a real option for forest owners. Continuous cover regimes involve managing productive forests following relatively natural processes, without large-scale clear-felling but rather by selective harvesting of small areas or individual trees. CCF systems are focused on producing high-quality trees and harvesting them at a regular, consistent rate and a size which suits target markets.

New Zealand’s even-aged radiata pine plantations deliver valuable and increasingly recognised ecosystem services such as soil erosion control, improved water quality, carbon sequestration, and biodiversity benefits. These services generally increase as the forest grows towards harvest age, but are then lost at clearfelling, and are not regained until the forest is successfully re-established and achieves canopy closure. In contrast, CCF systems by their nature operate in a relatively ‘steady state’. Not only can they produce a regular income stream for owners, but they also provide associated ecosystem services at a more-or-less consistent rate in perpetuity.

Small-scale forest owners (with forests of less than 1,000 ha) are estimated to own 536,000 hectares out of the total NZ plantation estate of 1,747,000 million hectares (MPI 2014). This portion of the forest estate is becoming increasingly important for wood production, because of the high proportion of privately owned forests that are now approaching harvest age. CCF systems are, in theory, well-suited to small forests, especially those where the landowner is closely involved in practical management.

There are some notable examples of successful small-forest CCF systems in New Zealand (Barton 2008), but a dearth of information and as a result, limited grower confidence, skills and infrastructure. Forest owners therefore continue with clear-felling regimes for want of an alternative. We hope to change this situation.

Our proposal

Target diameter harvesting is the CCF system used successfully by Dr John Wardle at Woodside, Oxford, North Canterbury (Wardle 2015). A recent detailed economic evaluation of the system (Perry et al 2015) produced encouraging results, suggesting that TDH can compete with conventional clear-fell systems.

The proposed project will produce an analysis and draw conclusions on the transferability of the ‘Woodside’ TDH system to other forests by:

  1. identifying the main practical requirements and constraints of introducing a TDH system to small forests of different sizes and on different land types, and
  2. a realistic assessment of the economic and market feasibility of TDH systems, particularly in the lower North Island.

Ultimately we hope to identify a set of key operational, market and economic criteria that will enable forest owners and managers to make an initial assessment about whether TDH is a viable option for their particular forest.


Four representative small radiata pine forests in the lower North Island will be selected in the following size classes: (i) 2-5 ha, (ii) 5-20 ha, (iii) 20-100 ha, and (iv) >100 ha. We will identify what we believe to be relatively typical plantations using our farm forestry networks, all with trees close to harvest age.

Operational feasibility will be assessed on the basis of access for ground-based harvesting and ease/economic viability of constructing access for log transport (trucks or forwarders). This will be assessed using commonly available harvest planning techniques verified by ground inspection.

We will identify logging contractors who have existing skill-sets and equipment required for TDH, or at least may be willing to acquire the necessary skills and equipment. We will invite at least one contractor to visit each of our selected sites to get their perspective on the operational feasibility of a TDH harvest, the costs involved and any particular operating constraints or considerations.

Economic feasibility will be evaluated using a similar approach to that reported in Perry et al. (2015). Standard forest inventory techniques will be used to take measurements in pre-harvest inventory plots in the four representative forests. Stands will be grown forward using commonly-used growth models to a series of TDH dates comparng TDH and conventional systems. Land Economic Value (LEV) will be used as the standard economic indicator. The contribution that income from carbon could make to post 1989 forests managed under TDH and clear-fell regimes will also be assessed.

Market feasibility will require consultation with transport/timber marketing professionals about implications and feasibility from their perspective.

We will interview representatives of the main harvesting and marketing companies in the lower North Island. The key questions are around what markets exist, and whether these markets will reliably accept relatively small but consistent annual volumes of logs produced by TDH, versus the normal paradigm for small forest owners where they hope to enter log markets at a time when demand is high, and market the entire available log volume in one large sale.

We will also make a qualitative assessment of the eco-system services associated with each woodlot for the record. The final output will be a report submitted to MPI and made available via the SFF website.

We will share the results of our study via industry journals and, if the results are positive, we will hold at least one field day, and undertake further extension activities.


Barton I (2008) Continuous Cover Forestry: A handbook for the management of New Zealand Forests. Tanes Tree Trust, Hamilton, NZ. 104 pp.

Perry C, Bloomberg M, and Evison D (2015) Economic analysis of a target diameter harvesting system in radiata pine. NZ Journal of Forestry 59 (4) p2-8.

Wardle J (2016) Woodside: A small forest managed on multiple use principles. NZ Farm Forestry Association, Wellington, NZ. 131 pp.

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