Table 3.4 Area of Indigenous Forest on Māori Land with No Current Productive Potential (1)

Region Nthlnd Aklnd Wkto BOP Gisbn H/Bay Tnki Mwtu/
Wang		 Wgtn Total
General Hardwoods 269 820 11601 8491 618 6114 0 6231 91 34235
Highland Softwood Beeches 0 0 87 0 779 0 0 0 0 866
Scrub 22,445 635 28,409 8640 53,297 12,677 176 8968 2015 137262
Others 22,530 383 16,405 18,495 4851 5827 43 3295 95 71924
Nga Whenua Rahui etc (2) 600 0 0 16,700(4) 3946 0 0 1728 0 22974
Total (without harvest potential) 45,844 1838 56,582 52,326 63,491 24,618 219 20,222 2201 267,261
Area Remaining with harvest potential (3) 19,941 586 38,899 99,309 10,344 19,851 1735 13,887 387 204,939

Notes:

  1. This is Māori land blocks greater than 10 hectares and within 2km of a road.
  2. The area included in this value has been rounded due to the small number of covenants that exist and the relative ease of identifying which blocks they apply to. While many small areas exist, this study has focussed on the large areas only. Many of the covenants cover large areas of land, only some of which supports merchantable forest. Where possible the values included here are for the area of merchantable forest only, not the total area of the covenant.
  3. The forest area contained in the table above represents the resource potentially available to support a sustained yield of timber and other forest benefits, with known non-productive and non-available areas deducted. Owners desire and attitudes to a sustained yield of timber have not been incorporated in these values.
  4. A large area in the Bay of Plenty of around 2000 hectares has been under consideration for a covenant, but harvesting has recently started in the block so it has been excluded from the Nga Whenua Rahui figures and included in the total productive area available. As discussed in Section 3.12, a reduction in available volume has been made to allow for the harvest that is currently underway.

3.9 Current Productive Potential on Māori Land

The section below considers what timber potential exists within this area of forest. The discussion has been divided into either individual regions or a grouping of two regions (where the area in those regions is not large).

It should be noted that the estimated merchantable volume per hectare is not high for most species. There are a large number of variables that must be accounted for within any estimation, and it is prudent to err on the side of caution. Factors that influence this estimation include:

  • The Nicholls classes are broad classes and are not able to fully adjust for the natural variation that occurs over a forest area due to natural features. For example within most forest types it is normal for the vegetation in the gullies to be different to that existing on ridges. In much of the North Island it is common for gullies to have a range of scrub hardwoods and pungas, with few if any timber trees present. The total area represented in that class will include areas of low timber volumes, such as these gullies, which in turn will reduce the average volume per hectare over the entire class.
  • In many areas there are site-specific issues that adversely impact on the potential of the forest to support a sustainable harvest of timber. These have been addressed in each regional discussion where they are known to exist.
  • While best endeavours have been used to ensure the accuracy of the data, not all areas can be ground truthed. In a resource such as this there will be areas that have been harvested, but are still represented in the data as having a full complement of timber, when in reality they will have significantly lower volumes.
  • The requirements of the FAA include the need to reserve some areas and to be confident that any yield from the forest is sustainable. Thus any approved Plan will tend towards the side of caution to ensure the forest is not being overexploited.
  • Many of the trees that make up the forest are defective in terms of timber potential. Thus there can be a significant difference between the standing volume, and the merchantable volume. Clearly any proposal for harvesting must be based around the merchantable volume. Under the terms of any Plan approved through the FAA process, trees that are felled and subsequently found to be defective are still considered to be part of the volume allowed in the annual harvest.
  • Some of the classes contain a range of species making up the canopy. A distinction between the volume of merchantable species and non-merchantable species is required. For example of the five beech species present in New Zealand two (red and silver) are considered as merchantable while two more (hard and black) have some potential as timber species, but are significantly more difficult to process. This issue is further compounded by the effect of altitude. A species such as silver beech growing at low altitude is considered as merchantable, but if growing at high altitude is generally of poor form and non-merchantable.

Given the factors above, the volumes provided in the following tables should generally represent a conservative estimate. In order for a Sustainable Forest Management Plan to be approved for any given area of indigenous forest, the FAA requires a detailed inventory of the timber present in the forest, and forest-specific calculations of the yield that forest can sustain. This study cannot in any way replace that requirement.

3.10 Northland and Auckland

Table 3.5 below provides an estimation of the volume of timber currently standing on Māori land in the Northland and Auckland Regions as a combined total. It should be noted that the Auckland Region is only a minor contributor to the total.

Table 3.5 - Estimation of Volume of Timber on Māori Land in Northland & Auckland Region

Estimated Volume (m3)
Forest Class Area (hectares) Estimated Timber Volume Range (m3/ha) Weighted Volume (m3/ha)
Kauri-softwood-hardwoods 14,921 0-95 35 522,235
Rimu-general hardwoods 217 0-60 30 6,510
Rimu-tawa 565 30-80 50 28,250
Rimu-taraire-tawa 3,640 30-80 50 182,000
Taraire-tawa 1,182 0-60 25 29,550
Total 20,525   768,545

A significant proportion of the Auckland Region resource is located on Great Barrier Island. This may pose some particular issues should a proposal to develop a management system be contemplated.

As can be seen from the table the major forest class contains some kauri. A significant proportion of this is likely to be second growth kauri that does not have the same properties as the old growth with which most people are familiar. In particular, these trees do not contain the heartwood of the old trees. As such they do not command the price premium associated with old growth kauri.

3.11 Waikato

Table 3.6 below provides an estimation of the volume of timber currently standing on Māori land in the Waikato Region, along with a discussion of some important issues that could impact upon the size of the resource.

Table 3.6 - Estimation of the Volume of Timber on Māori Land in the Waikato Region

Forest Class Area (hectares) Estimated Timber Volume Range (m3/ha) Weighted Volume (m3/ha) Estimated Volume (m3)  
Beeches 3548 0-100 55 195,140 Note 1
Highland & Steepland Softwood Beeches 1148 0-50 15 17,220
Rimu-general hardwoods-Beeches 1390 40-150 75 104,250 Note 1
Kauri Softwood Beeches 8136 0-90 50 406,800
Rimu-tawa 8395 50-150 75 629,625
Rimu Matai Hardwoods 1897 20-200 30 56,910
Tawa Beeches 51 40-100 50 2,550
Softwoods 225 50-350 100 22,500
Tawa 14025 0-100 35 490,875
Taraire Tawa 84 0-100 40 3,360
Total 38,899 1,929,230

Note:

  1. Much of the land that supports these classes is associated with the Lake Taupo Forest Trust (LTFT), which also has extensive involvement in plantation forestry. At present it is considering the potential offered by seeking Forest Stewardship Council (FSC) certification of its forest assets. While the majority of this process will focus on whether the Trust is sustainably managing its plantation forests, part of the Certification process will consider what, if any, impact its activities have on any indigenous resource it also has. The FSC process does not preclude the management of indigenous forests per se, but if the majority of the asset is plantation, FSC are likely to look unfavourably on any proposal to also harvest timber from the indigenous estate. FSC would prefer to see the indigenous part of the estate protected. The LTFT have thus indicated that it may not wish to consider sustained yield proposals for these indigenous forests at the present time.

In view of these comments, it is deemed prudent to reduce the potential volume available by the amount standing on this land. Thus a reduction of 300,000m3 from the total volume would bring the available volume to 1,629,230 m3.

3.12 Bay of Plenty

The Bay of Plenty Region contains the largest area of Māori land that continues to support indigenous forest. Table 3.7 below provides an estimation of the volume of timber currently standing on Māori land within the region.

Table 3.7 - Estimation of the Volume of Timber on Māori Land in the Bay of Plenty

Forest Class Area (hectares) Estimated Timber Volume Range (m3/ha) Weighted Volume (m3/ha) Estimated Volume (m3)  
Beeches 950 0-150 30 28500 Note 1
Highland & Steepland Softwood Beeches 4087 0-150 25 102,175
Rimu-general hardwoods- Beeches 2004 10-200 35 70,140 Note 2
Kauri Softwood Beeches 45 0-100 30 1350
Rimu-tawa 8016 50-150 70 561,120 Note 3
Rimu Matai Hardwoods 11999 20-200 60 719,940
Tawa Beeches 8833 40-100 50 441,650
Rimu Tawa Beeches 40507 30-150 55 2,227,885 Note 3
Softwoods 55 50-350 100 5500
Tawa 22810 0-100 30 684,300 Note 3
Total 99,306 4,842,560

Notes:

  1. Much of the region's beech forest is in the East Cape area, which suffered significant damage from Cyclone Bola in 1988. Many ridges had the majority of their forest cover destroyed during this event. In addition much of the remaining beech resource is of reasonably low quality from a timber perspective. Thus the standing merchantable volume is not high.
  2. The beech component of much of this resource is hard beech. This species has traditionally been very difficult to successfully saw and dry. As there is a significant hard beech resource throughout NZ, work on resolving this issue is continuing with good prospects of the species becoming suitable for processing. In the meantime however, the volumes have been lowered to reflect the lack of markets for this species.
  3. Harvesting of a significant Māori owned block of around 2000 hectares has been occurring in the Tauranga area under a Sustainable Forest Management Permit. This area had also been under consideration for a Nga Whenua Rahui Covenant. Either of these events effectively restricts any future volume of timber that can be harvested from the land. As a result it is deemed prudent to reduce the volume available by an amount to reflect the size of this area. The volume involved is estimated to be 66,000m3, which, for simplicity is spread over the rimu-tawa, rimu-tawa-beech, and tawa forest classes. This leaves a volume for the Region of 4,776,560 cubic metres.
  4. Appendix One has details of the forest classes and photos of some for the common classes found in the Bay of Plenty area.

3.13 Gisborne

Extensive land clearing activity in the early 1900s has seen the forest cover in the Gisborne Region dramatically reduced and this is reflected in the area of indigenous forest remaining on Māori land. Table 3.8 below provides an estimation of the volume of timber currently standing on Māori land in the Region.

Table 3.8 - Estimation of the Volume of Timber on Māori Land in the Gisborne Region

Forest Class Area (hectares) Estimated Timber Volume Range (m3/ha) Weighted Volume (m3/ha) Estimated Volume (m3)  
Beeches 295 0-100 30 8850
Highland & Steepland Softwood Beeches 127 0-50 10 1270
Rimu-general hardwoods -Beeches 0 30-100 0 Note 1
Rimu-tawa 1234 40-120 70 86,380 Note 2
Tawa Beeches 3742 20-70 20 74,840 Note 3
Rimu Tawa Beeches 4945 20-100 50 247,250 Note 3
Tawa 0 0-70 0 Note 1
Total 10,343 418,590

Notes:

  1. Areas of these forest classes are found within the area under consideration, but a significant proportion are currently within Nga Whenua Rahui Covenants and have therefore been deducted from the potential volume available for harvest.
  2. Approximately half the area of this forest class is within Nga Whenua Rahui Covenants and has therefore been deducted from the potential volume available for harvest.
  3. Much of this forest class contains hard beech, which as discussed elsewhere in the report, has limited current potential for management due to processing difficulties. This could change with improved technology.
  4. An additional area that contains significant timber volume is currently under consideration for either a covenant or a Sustainable Forest Management Plan.

3.14 Hawkes Bay

Table 3.9 below provides an estimation of the volume of timber currently standing on Māori land in the Hawkes Bay Region.

Table 3.9 - Estimation of the Volume of Timber on Māori Land in the Hawkes Bay

Forest Class Area (hectares) Estimated Timber Volume Range (m3/ha) Weighted Volume (m3/ha) Estimated Volume (m3)  
Beeches 11,512 0-300 25 287,800 Note 1
Highland & Steepland Softwood Beeches 111 0-80 5 555 Note 2
Rimu-general hardwoods- Beeches 5380 10-150 45 242,100
Rimu-tawa 413 50-150 60 24,780
Rimu Matai Hardwoods 1564 20-200 55 86,020
Rimu Tawa Beeches 436 30-130 60 26,160
Softwoods 266 50-250 100 26,600
Tawa 169 0-80 30 5070
Total 19,851 699,085

Notes:

  1. A significant proportion of the Hawkes Bay beech resource is higher altitude forest containing varying percentages of mountain beech. Thus the average volume per hectare has been adjusted to reflect this. By comparison, much of Maungataniwha Forest in Hawkes Bay carries a standing volume of over 200m3 per hectare. This is considered to be some of the best beech forest in Hawkes Bay. This volume is considerably higher than the values used in the calculations in the table, but these levels of reductions are justified to ensure that these estimates are conservative.
  2. Most of the highland and steep-land softwood-hardwood class is at higher altitudes and thus contains few, if any, merchantable trees per hectare.

3.15 Manawatu-Wanganui

Table 3.10 below provides an estimation of the volume of timber currently standing on Māori land in the Manawatu-Wanganui Region. Much of this resource is in the upper Wanganui River-Taumaranui area

Table 3.10 - Estimation of Volume of Timber on Māori Land in Manawatu-Wanganui Region

Forest Class Area (hectares) Estimated Timber Volume Range (m3/ha) Weighted Volume (m3/ha) Estimated Volume (m3)  
Beeches 244 0-200 60 14640
Highland & Steepland Softwood Beeches 0 0-50 0 0 Note 1
Rimu-general hardwoods- Beeches 0 20-100 0 0 Note 1
Rimu-tawa 3610 40-130 60 216600
Rimu Matai Hardwoods 354 20-200 45 15930 Note 2
Tawa Beeches 1137 0-100 20 22740
Rimu Tawa Beeches 4142 30-120 45 186390 Note 3
Softwoods 30 50-300 100 3000
Tawa 4370 0-80 30 131100
Total 13887 590400

Notes:

  1. No area is included for these classes as the majority of the class is contained within a Nga Whenua Rahui Covenant and is thus currently precluded from harvest.
  2. A significant reduction in the area of this class has been applied to account for Nga Whenua Rahui Covenants.
  3. The species of beech found within this class is predominantly black, which has limited current merchantable value. Thus no volume has been attributed to beech within the class. There will in fact be pockets of beech of merchantable species within the region, but they make up a small part of the total resource.

3.16 Taranaki and Wellington

Table 3.11 below provides an estimation of the volume of timber currently standing on Māori land in the Taranaki and Wellington Regions combined. These two regions have been combined primarily due to the small area of Māori land that supports indigenous forest within each region.

Table 3.11 - Estimation of Volume of Timber on Māori Land in Taranaki & Wellington Regions

Forest Class Area (hectares) Estimated Timber Volume Range (m3/ha) Weighted Volume (m3/ha) Estimated Volume (m3)  
Beeches 59 0-200 0 0
Highland & Steepland Softwood Beeches 308 0-75 35 10780
Rimu-general hardwoods- Beeches 20 10-200 30 600
Rimu general hardwoods 295 10-100 30 8850
Rimu-tawa 398 40-140 50 19900
Tawa Beeches 80 0-100 20 1600
Rimu Tawa Beeches 669 20-120 50 33450 Note 1
Tawa 292 0-80 30 7300
Total 21 82,480

Note:

  1. The major beech species in this class is hard beech, which presently is not considered merchantable. As a result no volume has been attributed to the beech component of this class.

3.17 Summary of Standing Volume Estimates

Table 3.12 below shows the area of indigenous forest on Māori land that ha a productive potential and is not currently constrained by reserves, to be about 204,000 hectares. The forest estate has a conservative standing volume of over 9 million cubic metres.

Table 3.12 - Estimation of the Volume of Timber on Māori Land by Region

768,545 1,629,230 4,776,560 418,590 699,085 590,440 82,480 8,964,930
Region Area (hectares) Estimated Volume (m3)
Northland and Auckland 20525
Waikato 38899
Bay of Plenty 99306
Gisborne 10343
Hawkes Bay 19851
Manawatu-Wanganui 13887
Taranaki and Wellington 2121
Total 204,932

Table 3.12 above shows the area of indigenous forest on Māori land that has a productive potential and is not currently constrained by reserves or similar issues to be about 204,000 hectares. This forest estate has a conservative standing volume of about 9 million cubic metres.

Another way of looking at the resource is by forest class. This is useful when considerations of growth and the class of forest that is available. Table 3.13 below provides a summary by forest class.

Table 3.13 - Summary of Forest Area on Māori Land by Forest Class

Forest Class Area (hectares) Estimated Timber Volume Range (m3/ha) Volume Range Used (m3/ha) Estimated Volume (m3)  
Beeches 16608 0-300 25 - 60 339790 Note 1
Highland & Steepland Softwood Beeches 5781 0-150 0-35 132000
Rimu-general hardwoods 512 0-100 30 15360
Rimu-general hardwoods- Beeches 8794 10-200 0-75 312840  

Note 1
Rimu-tawa 22613 40-130 60 1544655 Note 1
Rimu Matai Hardwoods 15814 20-200 45 938795
Tawa Beeches 13843 0-100 20 543380
Rimu Tawa Beeches 50699 30-120 45 2699135 Note 1
Softwoods 576 50-300 100 57600
Tawa 41666 0-80 30 1480820 Note 1
Kauri softwoods Hardwoods 23102 0-100 30-50 930385
Taraire tawa 1266 0-100 30-40 32910
Rimu taraire tawa 3640 30-80 50 182000
Total 204914 9209670

Note:

  1. The volumes shown in this table have been adjusted to allow for areas that are not formally reserved, but at this stage appear unlikely to be available for management due to other considerations such as FSC requirements as discussed in Sections 3.11 and 5.3.2.

While this resource is spread over a large number of owners and over a wide geographical area, it nevertheless is a very significant asset, which even at minimal stumpages has a very considerable value in economic terms as discussed in Section 4.7.1.

A forest estate of this magnitude also has a very significant ecological value that can be protected and enhanced provided correct management is applied. The process of developing and implementing a Sustainable Forest Management Plan can be a major step towards ensuring that the asset is valued for both its economic and ecological worth.

3.18 Forest Health

Any analysis of the potential for a forest to yield a sustainable harvest of timber needs to examine the health of the existing forest resource. This report is only able to comment on the health of Māori owned forests in a very generic manner. It will become more important as any work progresses towards developing proposals for a specific forest area, to examine in detail the health of the forest resource, and to consider what, if any, action is required to improve the health of the forest.

In this sense it is necessary to elevate the discussion above the health of single trees and to consider the health of the total ecosystem, inclusive of the trees. Further when considering the tree component of the forest, this must be inclusive of all levels within the forest and of all species, not just those that contribute to the timber potential. The requirement of the FAA is the long-term sustainability of the forest as a viable ecosystem, capable of inter alia, a harvest of timber in perpetuity.

Without the entire ecosystem being healthy and viable there can be no permanent sustained yield of timber and other forest product from the forest. Bearing this in mind however, it is important to remember that a forest being managed to provide a sustained timber yield will be manipulated to favour the timber species. Provided the scale of forest management activity is within the ability of the forest to recover, a subtle change of species composition over a period covering decades or even centuries is unlikely to be interpreted as being unsustainable.

As discussed above this is an issue to address on a case-by-case basis when developing Sustainable Forest Management Plans.

What is required for this report is to consider what macro issues exist that could adversely affect the ability of Māori owned forests to produce a sustained yield of timber.

The current environment existing within the indigenous estate in NZ (both private and State) can at best be described as perilous and at worst approaching a disaster. The impact introduced pests (plant and animal) have had on the forests has been enormous and largely continues unchecked. There are obvious signs such as the decline in some bird species (due to predation and competition for resources) and general poor health of canopy trees due to possum browse in particular in many areas. What is less obvious is the long-term effect of these changes on the ability of the ecosystem to sustain itself whether there is a harvest of timber or not. These issues may well be compounded if the threat of global warming and other macro influences come to pass.

On the positive side of the ledger, the management of many of the larger animal pests and of invasive plant pests in areas under Sustainable Forest Management Plans will support the forest ecosystems inherent ability to sustain itself.

In many cases the extraction of small volumes of timber have resulted in a more diverse range of indigenous species within the forest and thus a wider range of habitats for other flora and fauna.

Studies in old growth forest in Whirinaki showed the number of bird species present increased after small volumes of timber were harvested due to the increase in habitats and food sources available. In particular, the presence of many seral plant species was advantageous to bird species that relied on the additional food sources that these seral species provided.

Significant areas of Māori owned forest have been harvested in the past and these forests will require additional resources to manage plant pests that are already established and to assist the development of timber species in the regenerating forest. In the past there was generally little care taken to ensure weed pests were not brought into a forest on machinery or in road metal. Thus species like gorse and broom have become established in many areas of natural forest.

It is clear that throughout NZ there is a need to focus on improving the health of indigenous forests and in particular managing the introduced pests. The implementation of a Sustainable Forest Management Plan within a forest is likely to be an important step in providing the owners with an incentive to achieve this.

Many of these forests have also suffered significant changes to their wind profile and in some areas this is having an adverse effect on the residual forest. Tawa in particular can suffer from significant dieback within the canopy due to greater exposure to wind and possibly frost.

There is little that can be done to alter this situation in forests that have been previously harvested apart from monitoring the health of the residual stand, and if harvesting is to continue on a sustainable basis, to attempt to preferentially harvest those trees that are most severely affected. By preferentially harvesting trees that are in poor health the overall stand should become more resilient through time. The planning of any management operations should also be completed with these problems in mind and means of mitigating them sought.

Within beech forests a significant forest health issue is the impact of pinhole borer. These are naturally occurring insects throughout most of our beech forests but appear to be more prevalent in the South Island. These borer feed on dead wood within the forest. Following any harvest operation there is an increase in the amount of wood (ie food) within the forest, which allows the borer population to expand. Following such a population expansion there is a strong possibility of the insects turning their feeding attention to the residual live trees. While such an attack is unlikely to kill the trees, it can severely degrade the value of the timber from these trees.

The message here is that very good forest hygiene is required if there is to be any sustainable harvest of timber from beech forests. There is also a strong likelihood that any Māori owned beech forest that has a previous history of harvest may have already suffered some attack from pinhole. This needs to be checked within the forest as part of the process of developing a Sustainable Forest Management Plan.

3.19 Recoverable Volumes

The potential of any forest land to support a sustainable harvest of indigenous timber ultimately comes down to the volume of merchantable timber currently standing on the land, which is both available (ie not protected) and within certain economic constraints, and the ability of that forest to replace the volume removed by harvesting.

For many areas of Māori land, a proportion of the potential volume has already been removed during previous harvesting activity. The effect this has on the ability of a given forest to produce a sustainable harvest needs to be considered on a case-by-case basis. In the big picture though there are some regional and forest class differences.

In the north, the kauri forests were in general harvested quite early (eg in the late 19th and early 20th century), and have thus had time to regenerate to a significant extent. For the rimu forests of the central North Island, the harvesting was more recent and thus the recovery of the forest is not as advanced. In addition, for some of these latter forests the forest class has changed as a result of the removal of the softwood component.

It is against this background of forest modification that we must consider the ability of the remaining forests to support a sustained harvest of timber.

The ability of the forest to produce a harvest is influenced by the current basal area status of the forest and the diameter distribution of the trees present. For the second growth kauri stands in Northland, they will be producing a lot of increment, but much of this will be too small in diameter to give an immediate harvest. As the trees grow into larger diameters, the opportunity to extract a sustainable harvest will improve.

For the more recently harvested rimu-tawa stands found in the Bay of Plenty, the ability of the forest to produce a harvest is a lot more dependent on the residual old growth trees. Any regeneration that is present will in many cases be too small at this stage to contribute much to the standing volume.

When examining the literature for studies of growth rates for indigenous species most studies consider the ability of an individual species to grow, rather than how that species reacts in a mixture of species as is commonly found in a forest. The table below shows the growth rates exhibited by some of the species studied as pure stands.

Table 3.14 - Growth Rates in Pure Stands

Species Rotation length (years) Increment (m3/ha/yr)
Kauri 150 5 -12 (or more on some sites)
Rimu* 200 1 - 2
Totara 100 -150 1 -8 (or more in plantations)
Tawa 200 0.5 - 1
Beech - Red 60 - 80 6 - 9
Beech - Silver 80 - 100 4 - 7
  • This is for North Island rimu, not West Coast terrace rimu.

In a natural forest it is unusual to have pure stands with the exception of the beech species. More commonly the forest is made up of a range of species that interact with each other to give a variety of growth rates.

The forests under consideration in this report cover the full range of classes over a very wide range of sites. Very significant areas are of beech species that has had little or no modification and are able to achieve higher growth rates than the rimu - tawa forest and associated forest classes. In addition the kauri stands are also able to add increment at a very good rate. Against this must be offset the areas where the forest has little or no growth potential in the foreseeable future due to either environmental factors or to past exploitation.

As suggested in the book "Indigenous Forestry - Sustainable Management" by the Ministry of Forestry and the farm Forestry Association, it is wise to err on the side of caution when calculating what the sustainable harvest of a natural forest might be. It is relatively easy to increase the harvest level in the future if the early estimates are low. On the other hand, if the early cut has been too high, decreasing the cut can be far more difficult if there are now markets and businesses reliant on the supply.

Newton in his address to the "Māori and the Business of Forestry Conference 1998" suggested a "safe sustainably harvestable annual increment is in the range of 0.5 - 1.5 m3 per hectare per annum". Given the diversity of forest classes present on Māori land and the highly variable history of harvesting they have been subjected to it would indeed be wise to be cautious when estimating the potential for these forest to provide a sustained yield.

It would take a considerable research effort to quantify the increment of these forests with any degree of confidence. This level of research would be better directed at individual forests once the owners had decided they wish to consider the potential of developing a Sustainable Forest Management Plan.

For the purposes of this study it is useful to gain an appreciation of the magnitude of sustainable yield over the estate. To achieve this it is necessary to make assumptions about the increment that the forests can produce. From the data provided above a conservative increment allowance of 0.35m3/ha/year has been used. This is based upon 75 percent of the lower end of Newton's values and is well under the ranges of values provided for single species stands.

It must be recognised that the different forest classes have different increment potential. For example the kauri stands in Northland may well have increments of 2 - 5 m3/ha/year and the beech stands could also achieve levels approaching this. Conversely the rimu-tawa stands may well be below that 0.5m3/ha/year level and in some cases may have no increment at all. (In severe cases or in over-mature stands there may even be decrement of total volume). The rimu-tawa forests and the pure tawa forests where the rimu has been removed make up a significant percentage of the total forest area and thus have a commensurate effect on the weighted average increment that can be produced. Stands that have been subjected to earlier harvests are likely to be supporting basal areas below the "carrying capacity" of the site. This can offer the opportunity for the site to add higher levels of increment if there are sufficient stems. Conversely if the early logging has been intense, there may be insufficient stems to fully utilise the growth potential and thus increasing basal area is reliant upon regeneration.

Table 3.15 below provides an indication of the increment that could be potentially available for harvest from Māori owned indigenous forests, based upon an increment of 0.35m3/ha/year. The table also provides some indication of the sensitivity of these figures.

Table 3.15 - Estimation of Annual Increment produced by Indigenous Forests on Māori Land (204,000 hectares)

Increment
(m3/ha/year)		 Theoretical Harvestable Volume (m3/year)
0.2 40,800
0.35 71,700
0.5 102,425
0.75 153,000
1.0 204,800

It can be seen from the table that the annual increment produced within a forest has a very large impact upon the total available resource. It should also be noted that the annual increment is in effect the volume that can be harvested in perpetuity with no loss of standing volume in the forest. For these forests, the extent of regeneration occurring and the fact that the basal area is below that the site is able to support (due to earlier harvests), it is likely that not all the annual increment can be harvested. This is due to some of the increment being on trees that are not large enough to be considered merchantable. It is therefore reasonable to assume the total annual increment could increase through time as more of the standing volume is within the merchantable size classes.

This is a strong incentive for the forest manager to optimise their management in ensuring the health and vigour of the forest. As the table shows a very small increase in the annual increment can give significant gains in available volume over an estate.

3.20 Regeneration Potential

The major requirements of the FAA are threefold. Firstly there is the matter of how much timber can be removed from the forest; secondly there is the requirement to ensure the ecological values of the forest are not lost or unduly compromised; and thirdly the Act requires the forest manager to ensure there is adequate regeneration of the species removed through harvest to replace the volume removed.

The regeneration issue can be addressed primarily in two ways. In some forests there is significant natural regeneration of the timber species that is able to replace the removed trees. In other forests there is little or no advanced regeneration present at the time of harvest. In these forests, the manager must take action to replace the harvested trees, either through encouraging natural regeneration, or by artificial means such as planting seedlings.

There can be many reasons for the lack of natural advanced regeneration in these forests. The most common reasons are outlined below:

  • The activity of introduced animals such as deer and possums feeding on the seedlings as they grow, generally resulting in the development of an under storey consisting of unpalatable species.
  • Rats and mice that eat the seed as it falls thus preventing the development of regeneration.
  • The ecological and environmental conditions being such that they prevent the development of regeneration of the timber species. This often results in a change of forest type through time, from a forest dominated by one species to a forest dominated by another species. A good example of this is found in the dense podocarp stands in the Whirinaki area where there is little regeneration of podocarp species within the existing forest, but instead an under storey of hardwoods is developing. Through time the forest will change from a podocarp forest to a hardwood forest.

Given the requirements of the FAA to ensure regeneration, the pre-harvest status of the regeneration and the factors that impact upon this become very significant to the manager. Clearly there is a significant cost associated with the artificial establishment and management of seedlings, but even in forests where natural regeneration is present there remains a need to control and manage introduced animal populations and weed pests.

The development of a Sustainable Forest Management Plan should include a determination of what regeneration is present, how this can be managed, and how additional natural regeneration can be encouraged. In addition the question of what changes to management techniques are required to support the growth of timber species and what if any supplementary planting will be required will also need to be addressed.

The Act also prescribes the size of any coupes that are to be used during harvesting. For the softwoods and kauri only single trees (or very small groups of trees) can be removed during a felling cycle. No further harvest can occur adjacent to this site until the site has recovered from the harvest and the next crop of trees is established.

For beech, small coupes (preferably no bigger than 0.2 ha, but legally up to 0.5 ha) are permitted. This recognises the significant response of the beech species to openings in the canopy and subsequent increased light levels. In this situation all trees within the coupe are likely to be removed in a single harvest. As with the softwoods no further harvest in the immediately adjacent forest is permitted until the coupe has been successfully regenerated. For the forest owner wishing to harvest using small coupes, it is essential that regeneration of harvested areas occur as quickly as possible. If this does not happen future harvests will become severely constrained.

For light sensitive hardwoods (such as tawa), harvest is only permitted by means of single trees or very small groups in a similar way to the softwoods.

For all harvests, low impact harvesting is required to minimise the impact upon the residual forest, and to enhance the ability of the forest to recover.

While all this may seem to be very prescriptive, without a focus on the long-term replacement of the trees harvested, the forest cannot be sustained and therefore the Plan cannot be supported or approved.

It is in these technical areas that any owner contemplating the development of their natural timber resource is most likely to require professional assistance.

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Contact for Enquiries

Policy Analyst - Forestry
Innovation and Research
MAF Policy
Ministry of Agriculture and Forestry
PO Box 2526
Wellington
NEW ZEALAND

Tel: +64 4 894 0100
Fax: +64 4 894 0741
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