Why It Works
Plantation designs for ease of sequential and selective harvest
Since 2001, the Mitchell Forest Farming plantation designs incorporate compatible mixed species configurations to facilitate ease of sequential and selective harvest. Our planting plans with 3 m x 3 m spacings always take into account future commercial harvest of high quality timber from a range of species with varying rotation lengths – after all that is what we are all about.
A feature of these new Mitchell Forest Farming plantation designs is the roles of the fast-growing high value timber species silver quandong (Elaeocarpus grandis) for commercial thinning/early harvest at 8-10 years and for promoting the height and clearwood stems of the other timber species.
Silver quandong has always been Jack Mitchell’s keystone species. Since Jack’s confirmation of the consistent high quality of silver quandong trees at early harvest (8 years) in a demonstration planting at Samford in 2001, the design of Mitchell Forest Farming plantations have taken into account the potential of this species for early commercial harvest and cash flow.
Silver quandong trees now comprise more than 60% of the Mitchell Forest Farming Plantations. Every second row is entirely silver quandong and in the alternative rows it is one in four. The thinning/early commercial harvest of these silver quandong rows results in a 3 m to 6 m spacing for optimal growth and future sequential and selective harvesting of the remaining trees.
The harvest of all trees in the entire silver quandong rows at 8-10 years (depending on seasonal conditions) provides an early return on the investment for the grower and effectively ensures that the thinning/early harvest operation from 1000 to 500 stems per hectare at this stage does not cause collateral damage to the other trees in the plantation.
Private growers are advised that in order to estimate the harvestable yield of silver quandong trees as well as the trees of other species as they reach a millable size for sequential and selective harvesting, to save costs one or two full rows can be measured to determine the average for a plantation.
After 25 years of self-funded research and continuous improvement Jack’s planting plans and species configurations in the Mitchell Forest Farming plantations always take into account future harvest and can be relied on to deliver results. Jack emphasises that if his methods are adhered to everything will fall into place with predictable outcomes. It is only in research plantings that trees need to be measured regularly to determine their growth rates. For private growers there is no need to regularly measure and monitor the trees until just prior to harvest.
Plantations based on compatible mixtures of commercial timber species
The species used in the Mitchell Forest Farming plantation designs are based on years of research and experimentation into identifying species with the potential to produce quality timber as well as compatibility with the other species used in mixed species configurations. In well planned mixed species plantations, species that differ in terms of their canopy structure and growth rates utilise the available resources – light, nutrients and water - in a way that is complementary for mutual growth rather than competitive.
Although the science and methodology of mixed species plantations is still relatively new globally it is clear that mixed species plantations offer the potential for higher biomass production and carbon storage than monocultures. The increased and diversified yields in addition to higher future economic returns offset the increased costs associated with establishing and managing a mixed-species plantation.
Mixed species plantations meets aesthetic and environmental outcomes and offers a number of advantages for the grower over conventional monocultures – the spread and diversification of harvestable products, lower potential for pest and disease outbreaks and the creation of diverse habitats for native fauna.
Only species with the potential for timber production used in plantations
All the species in our plantations are commercial timber trees, with no non-commercial or 'pioneer' species. At a spacing of 3 m x 3 m, the planting density approximates 1000 trees per ha.
There are a number of inherent advantages of using native species in mixed species timber plantations. Native species are readily available and observable for their potential for timber production in the wild; they adapted to local climatic and environmental conditions; they have environmental and conservation values and their seeds are available in season.
This is not to say that all native rainforest tree species have the potential for commercial timber production for the private grower, even if they have been prized as timber trees in the wild. Jack uses only those species that perform well in cultivation and have the commercial potential for timber production.
The species list for any particular Mitchell Forest Farming plantation depends on location, soil type and rainfall. At the present we are using a mix of 4-6 species in timber plantings out of a total species list of 10. The 10 species in our plantations are:
1. Silver quandong Elaeocarpus grandis
2. White cedar Melia azedarach
3. Silky oak Grevillea robusta
4. Silver ash Flindersia schottiana
5. Queensland maple Flindersia brayleyana
6. Yellow ash Flindersia xanthoxyla
7. White beech Gmelina leichhardtii
8. Crows ash Flindersia australis
9. Red Cedar Toona ciliata
10. Khaya Khaya senegalensis
The keystone species of any 'Forest Farming' planting is silver quandong (Elaeocarpus grandis). This species is dominant in natural rainforests and has a primary role in height promotion of the other species in our designed cabinet timber plantations. It consistently displays the fastest growth rates of the native cabinet timber species and it has a superb growth form in nature. The timber has a combination of strength, durability and versatility, and has always been highly prized with a ready market. This species now represents about 60% of the trees in our forest farming plantings.
In our plantings, native timber species are mostly used but in the future there may be at least one exotic species used. There is a need to produce a range of coloured timbers to satisfy the domestic and export market. One exotic species which we are now trialing is Khaya, otherwise known as African mahogany (Khaya senegalensis). Specimens we have are now seven years old and showing great promise with 12 to 15 metre clear trunks which have never been pruned. This is a red timber, almost like red cedar, but showing no sign of tip moth infection. We expect to have mill size logs at 12 to 15 years.
We have also had success with our red cedar (Toona ciliata) field research in controlling the tip moth (Hypsipyla robusta) by spraying with a systemic residual insecticide young growing shoots at strictly 10 day intervals during the growing season. When a four metre trunk is achieved, the tree is allowed to crown and no further insect control is necessary.
Forest Farming plantations have the potential and capacity to store carbon
The emergence of carbon markets in recent years has provided a potential source of funding timber plantation projects over time. We believe that carbon storage and timber production can be viewed as compatible objectives in future national carbon pricing and trading schemes. Planting and maintaining trees for eventual harvest will reduce our collective carbon footprint.
Mixed species plantings comprised of fast-growing rainforest timber trees have a greater potential for storing carbon than most other commercial and restoration plantings. Forest Farming timber plantations established for sequential and selective harvest on a regular rotation basis can absorb significantly more carbon dioxide over the plantation’s lifetime than a non-harvestable planting for a number of reasons:
• commercial timber plantings comprised of high value species are managed to optimise the production of wood and have higher rates of carbon storage;
• after sequential harvest there is minimal site disturbance and the high value timber products continue to store carbon off site; and
• trees remaining in the plantation after sequential harvest are freed up from the competition and removal of larger trees and there is a resultant pulse in carbon storage.
We collect our own seed and grow our stock under best practice conditions
Perhaps the main advantage for the grower of working with the Mitchell Forest Farming System is that we collect our own seeds throughout the season for the species used in the plantations, from selected trees in the wild and increasingly from seed orchards.
Through utilising a range of seed sources for timber tree species we ensure that we maintain genetic diversity in our stock and in the grower’s plantations to protect against extreme environmental events and pest and disease outbreaks.
The propagation of rainforest tree species requires a specialist approach and Jack Mitchell has been a leader over many years in the successful seedling production of valuable timber species previously considered too difficult to propagate commercially because of a number of characteristics including sporadic seed production, short storage life and delayed germination.
The quality of planting stock is one of the main determinants of productivity and commercial harvest from timber plantations. The tube stock that we supply to the growers from our nursery is always of high quality and the best available on the market. The tube stock delivered for planting is healthy and has been sun-hardened and grown under air-pruning conditions to promote vigorous root systems.
Our Forest Farming System is low-maintenance and environmentally sound
Natural forests provide a range of ecological services; from absorption of excess carbon dioxide, and the creation of fauna habitats to soil conservation and amelioration; from to the operation of water cycle and catchment protection, to sustainable yield of non-timber forest products such as honey, wildflowers and bush foods.
Over the past 25 years, Jack Mitchell, with the assistance of his son Ron and a team of dedicated researchers and field workers, has developed and refined a 'Forest Farming System' for the commercial production of valuable native cabinet timber tree species. This system is based on a low maintenance and ecologically sustainable approach that "learns from and works with nature" to achieve economic outcomes.
Timber plantations more often than not get a bad press. They are generally considered to be arboricultural equivalent of the chemically-dependent monocultural broad acre crops dominating the conventional agricultural landscape. The establishment of timber plantations is always and quite justifiably controversial when they are composed of exotic species, replacing naturally growing native forests, and planted to result in a uniform clear-felling operation.
The Mitchell Forest Farming System is the only timber plantation system in practice that uses compatible associations of native trees in carefully designed naturalistic 'mixed species' plantings that are designed for sequential and selective harvest – not clear felling - and are compatible with natural landscapes. With the Mitchell Forest Farming System natural ecosystem processes are fast-tracked and enhanced, and expensive ongoing inputs of irrigation, fertilizers and pesticides are virtually eliminated.
Our methods are based on years of study and observation of the natural growth patterns and compatibility of the species we use. When these trees are taken out of their natural rainforest environment to establish plantations, we must try and emulate a naturalistic approach in order to achieve the best results in terms of timber production. We therefore need to have a thorough understanding of how these trees have evolved in their natural state.
All rainforest trees gather their nutrients from the broken down leaf matter on the floor of the forest by the actions of micro-organisms which only exist in a full canopy cover of a rainforest micro-climate. One of the objectives to maintain the health of a plantation is the establishment of a canopy cover. This is accomplished by a mix of species designed to achieve a stratified canopy within the first two to three years.
We only establish mixed species plantations on already cleared land. To complement our mixed species plantings we encourage growers to establish use buffer zones along stream banks, with the effect of creating a wildlife corridor and a balanced ecosystem to enhance the health of our plantations as well as create habitats for native fauna and provide stream bank protection. As we use no fertilisers and very minimal irrigation after the initial planting, there is no nutrient runoff and the water quality of natural watercourses is maintained.
Plantations are ecologically sustainable from establishment to harvest
Timber plantations are now an essential component of agriculture and semi-natural landscapes to meet the increased demand for timber products. While timber plantations do not always produce all of the environmental and social benefits we associate with intact natural bushland, they can be planned to ensure compatibility with natural landscapes, to provide attractive short-term yields of high quality and high value timber, and to relieve the harvesting pressure on native forests.
Consumers of timber products the world over-including Australia - are becoming more concerned and informed about destructive environmental impacts associated with unsustainable and often illegal timber production from the world's native old growth forests. It is now generally accepted that forest resources - be they native forests or plantations - need to be sustainably managed. Consumers need to be assured of sustainable plantation management through verifiable ‘green’ timber certification schemes.
Timber certification is a market-driven consumer-centered mechanism to promote production from native forests and plantations. Our timber plantations are well designed and well managed from establishment to harvest, according to accepted indicators for ecological sustainability.
We advocate that private growers learn more about timber certification schemes. We would contend that our plantations would comply with the standards of independent third party auditing for the two forest certification schemes that are currently operating in Australia: the Forest Stewardship Council (FSC) and the Australian Forestry Certification Scheme (AFCS).
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