4 Wood availability forecasts

Readers are urged to thoroughly review these wood availability forecasts before using them for planning or investment decisions, or to engage a professional forestry consultant who can interpret the forecasts in the context of any such decisions.

This chapter describes the possible range of harvest volumes that could be available from the Nelson and Marlborough regions.

The wood availability forecasts are based on each region's forest resource and the forecasting assumptions noted. The forecasts incorporate harvesting intentions of the regions' large-scale forest owners (described in the previous section), and the views of forest managers and consultants, to ensure the forecasts represent a realistic range of future wood availability scenarios.

The range of scenarios clearly indicates that there are many different ways the forests in the region may finally be harvested. The availability of wood from the large-scale owners is reasonably certain, while the forecast availability of wood from the small-scale forest owners is less certain.

A key issue is the timing of harvesting by the small-scale forest owners. The timing will be driven by a range of factors including individual forest owners' objectives, forest age, log prices, demand by local wood processing plants, and perceptions about future log prices and future wood availability.

Harvesting of forests is managed to maximise the benefits to the enterprise that owns them. Each enterprise has its own harvest strategy based on the forest owners' objectives, market conditions and the forest estate that it owns or manages. Any change in harvesting strategies by a forest owner affects the age-structure and maturity of the forests it owns. This in turn directly affects future wood availability.

There are different levels of uncertainty associated with the wood availability from each component of the estate. The volumes forecast from the large-scale owners' estate, although subject to change because of changes in harvest intentions or changes in the resource description (areas and yields), have greater certainty than those forecast from the small-scale estate. Not only are harvest intentions less clear for small-scale owners, the resource description is less accurate.

Scenarios for radiata pine

The five harvest scenarios below were developed following consultation with the National Exotic Forest Description (NEFD) steering committee and feedback from interested parties in Nelson and Marlborough.

Scenario 1: Harvest all areas at age 30

The estate of all owners is assumed to be harvested at age 30.

Scenario 2: Large-scale owners harvest at stated intentions, small-scale owners harvest at age 30

Large-scale owners' wood availability is assumed to be at stated harvest intentions for 2005 to 2015. After 2015 the availability is not allowed to decrease.

The estate of small-scale owners is assumed to be harvested at age 30.

Scenario 3: Non-declining yield (NDY) - target rotation 30 years

Large-scale owners' wood availability is assumed to be at stated harvest intentions (as for Scenario 2). The total wood availability of radiata pine from the region is not allowed to decrease (a non-declining yield constraint is imposed).

Scenario 4: Split NDY - target rotation 30 years

This is the same as Scenario 3 except that the total wood availability of radiata pine from the region is allowed to step down from 2034 to 2037 (at the end of the current rotation). From 2037, total wood availability is again constrained so that it cannot decrease.

Scenario 5: Target rotation age variations

This is similar to Scenario 4, but target rotation ages of 28 and 32 years are also evaluated.

Scenarios for other species

One scenario is presented for Douglas-fir (all owners), and one for other (non-cypress) softwoods (large-scale owners only).

The scenarios for other species are based on the harvest intentions of large-scale owners for 2005 to 2015 with yield regulated in subsequent years. Target rotation ages are 40 years for Douglas-fir and 30-35 years for other softwoods.

The species categories of cypress, eucalypts and other hardwoods were excluded because yield tables have yet to be developed for them. Other softwoods (small-scale owners) were excluded because the area data available is believed to include some area in cypress species.

Data

Method used to obtain area

Area was obtained from the NEFD as at 1 April 2005. Area for large-scale owners was used unadjusted. The area of the non-professionally managed component of the small-scale owners' estate was reduced by 15 percent. This was done because the area in this ownership category is often reported as gross area rather than net stocked area. In addition, reductions were made to the area of over-mature stands in the small-scale owner estate (as described later in the report).

Method used to develop yield tables

In 2005, new yield tables for Nelson and Marlborough were developed in the following way.

Large-scale owners provided yield tables for their estate.
These were averaged on an area-weighted basis to get regional yield tables for each croptype.
Yield tables for old radiata pine (age 16+ years, planted in 1989 and earlier), Douglas-fir and other softwoods were then calibrated to match the harvest intentions data provided by large-scale owners. The assumption is that the harvest intentions data is the most accurate information available, as it is based predominantly on detailed inventory.
Yield tables for young radiata pine croptypes (planted in 1990 and later) were left unadjusted.
The yield tables developed for the large-scale owners' estate were also applied to the small-scale owners' estate.

Large-scale owners' harvest intentions

Large-scale owners were asked to provide details of planned harvest volume by log grade and area from 2005 to 2015. These harvest intention values were then included at the beginning of the forecasts to provide the most realistic wood availability forecasts over this period.

There is a projected drop of 151 000 cubic metres in the large-scale forest harvest from 2005 to the harvest intentions in 2006. This is a result of the larger than planned harvest in Nelson during 2005, which was due partly to the salvage of wind-thrown forest, and partly to the objective of longer rotation ages (letting the trees grow older before harvest).

Wood availability forecasts for Nelson

Assumptions

The wood availability forecasts for Nelson are based on the following assumptions.

All area is replanted (with a regeneration lag of one year), apart from 1205 hectares of planned deforestation. Replanting is as follows:
- Large-scale owners: all area is planted back into radiata pine (radiata pine planted back into the same silviculture, Douglas-fir and other softwoods planted back 50:50 into pruned and unpruned radiata pine tending regimes).
- Small-scale owners: all back into the same species and regime.
The area awaiting replanting as at 31 March 2005, i.e. to be replanted in the 2005 planting season, is included as area at age 0.
The total harvest for 2005 (all species) is 1 662 000 cubic metres (MAF estimate).
It was assumed any area of radiata pine in the small-scale owners' estate that was aged 36 or older would not be harvested: this resulted in the removal of 234 hectares from the area file.

Scenario 1

This scenario has all areas harvested at age 30. It indicates the "pure" (i.e. unconstrained) availability of wood from Nelson. This is basically a reflection of the age-class distribution. Figure 4.1 shows the age-class distribution of radiata pine in Nelson, and Figure 4.2 shows the wood availability. The low point at 2017 in Figure 4.2 occurs because of the small area (1325 hectares) at age 18 (Figure 4.1). The high point at 2024 in Figure 4.2 occurs because of the large area (5733 hectares) at age 11 in Figure 4.1.

Figure 4.2 indicates that wood availability does not have the potential to increase markedly over the next 15 years.

Figure 4.1: Age-class distribution of Nelson radiata pine - combined estate as at 1 April 2005

Figure 4.2: Nelson radiata pine availability under Scenario 1 - combined estate

Figure 4.2: Nelson radiata pine availability under Scenario 1 - combined
estate

Scenario 2

In this scenario, large-scale owners harvest at intentions and small-scale owners harvest at age 30.

Large-scale owners' estate

The age-class distribution of the large-scale owners' estate (Figure 4.3) indicates that there are over 1000 hectares in most age-classes up to age 29. The area at age 0 is the area awaiting replanting as at 31 March 2005, i.e. area to be replanted in the 2005 planting season.

For this scenario, the availability of wood from large-scale owners is based on stated harvest intentions for 2005 to 2015. After 2015 the availability is constrained to be non-declining (the volume available is not allowed to decrease), with a target rotation age of 30 years. The wood availability of large-scale owners (Figure 4.4) is forecast to be relatively static around 1.1 million cubic metres a year until 2027. The subsequent increase reflects the larger area in young age-classes (age 0 to 4) in Figure 4.3 as well as the higher yield (cubic metres per hectare) anticipated for younger stands.

Figure 4.3: Age-class distribution of the Nelson radiata pine estate - large-scale owners as at 1 April 2005

Figure 4.3: Age-class distribution of the Nelson radiata pine estate -
large-scale owners as at 1 April 2005

Figure 4.4: Nelson radiata pine availability under Scenario 2 - large-scale owners

Small-scale owners' estate

The age-class distribution of the small-scale owners' estate (Figure 4.5) is very irregular, with over 1000 hectares in ages 8 to 13 years (planted from 1992 to 1997) and much less area in all other age-classes. The key issue is how to forecast the availability from this estate: in particular, how the large area in ages 8 to 13 will be harvested:

at a fixed rotation age (Scenario 2);
over many years (Scenario 3);
over an intermediate number of years (Scenario 4).

Figure 4.5: Age-class distribution of the Nelson radiata pine estate - small-scale owners as at 1 April 2005

Figure 4.5: Age-class distribution of the Nelson radiata pine estate -
small-scale owners as at 1 April 2005

Combined estate

The wood availability from all owners is presented in Figure 4.6. The wood availability from the large-scale owners' estate is the same as presented in Figure 4.4. In this scenario (Scenario 2), all area in the small-scale owners' estate is assumed to be harvested at age 30. The fluctuations in the total volume harvested reflect the variation in the age-class distribution of the small-scale owners' estate.

The large increase in volume from 2022 (Figure 4.6) occurs when the large areas from the small-scale owners' estate in young age-classes (8 to 13) is harvested. The increase in 2022 is a consequence of the 2092 hectares planted in 1992 (age 13 in Figure 4.5) being harvested at age 30 years.

Fluctuations in harvest volumes of the magnitude shown in Figure 4.6 would be impractical because of marketing and logistics realities. There would not be enough harvesting capacity to cut all the volume available during the peak period, and it would be hard to get short-term sales contracts to cover this volume.

Figure 4.6: Nelson radiata pine availability under Scenario 2

Scenario 3

The third scenario is for non-declining yield (target rotation 30 years). Figure 4.7 indicates that, when the small-scale owners' estate is harvested to complement the large-scale owners estate, the total volume (radiata pine) available from 2006 to 2019 is 1.3 million cubic metres a year. This increases to 1.9 million cubic metres a year from 2023. There is a gradual increase because an extra constraint was added to the model so that the total volume could not increase by more than 10 percent annually. This was to simulate some of the logistical constraints faced if volume was allowed to increase unchecked.

This scenario is similar to the base case scenario adopted in the 2000 wood availability forecasts. However, it causes the small-scale owners' estate to be harvested at rotation ages that differ markedly from 30 years (Figure 4.8).

Figure 4.7: Nelson radiata pine availability under Scenario 3

Figure 4.8: Average radiata pine clearfell age under Scenario 3

Scenario 4

The fourth scenario is for a split NDY (target rotation 30 years). This scenario also gives a forecast wood availability of 1.3 million cubic metres a year from 2006 to 2019 (Figure 4.9). This increases to over 2 million cubic metres a year from 2023 before reducing to 1.7 million cubic metres a year from 2036.

Figure 4.9: Nelson radiata pine availability under Scenario 4

The main difference from Scenario 3 is that the large area of young stands in the small-scale owners' estate is assumed to be harvested over a shorter period of time. The total volume was not allowed to decrease between 2006 and 2034, that is, for the current rotation. After 2034 an annual reduction of up to 10 percent was allowed before the yield was required to be non-declining for the next rotation (from 2037). As a consequence, the average clearfell age for small-scale owners stays closer to the target of 30 years than was the case in Scenario 3 (Figure 4.10).

Figure 4.10: Average radiata pine clearfell age under Scenario 4

The total volume forecast for Scenario 4 is broken down by log grade in Figure 4.11. This shows that the pruned volume available is relatively steady throughout the forecast period despite changes in total volume.

Figure 4.11: Nelson radiata pine availability under Scenario 4 - by log product

Figure 4.11: Nelson radiata pine availability under Scenario 4 - by log
product

Scenario 5

Different wood availability profiles are generated if the target rotation age is changed from 30 years to either 28 or 32 years (Figure 4.12). Because of the limitations imposed by the current age-class distribution and large-scale owners' stated harvest intentions, average clearfell ages do not separate until about 2020 (Figure 4.13).

Figure 4.12: Nelson radiata pine availability for each target rotation age under Scenario 5

Figure 4.12: Nelson radiata pine availability for each target rotation age
under Scenario 5

Figure 4.13: Average radiata pine clearfell age for each target rotation age under Scenario 5

Figure 4.13: Average radiata pine clearfell age for each target rotation age
under Scenario 5