Design and Establishment
of Shelterbelts
The On-Farm Benefits of Timberbelts
Designing a Timberbelt to Capture Multiple Benefits
of Shelter, Timber Production and Nature Conservation.
Species Selection
Factors to Consider when Designing a Timberbelt
Shelterbelts are a valuable tool to landholders for the enhancement
of environment, productivity and natural habitat.
A timberbelt is a multi purpose shelterbelt which incorporates timber
production with other benefits.
It is not a substitute for the woodlot if single purpose timber
production is the aim.
However, a timberbelt is a viable option for producing timber which
does not require the devotion of large areas of land to a single
purpose and which can provide a range of other on- farm benefits
simultaneously.
A carefully designed timberbelt will produce timber while offering the
benefits of shelter to stock and crops.
Good shelter on farms can actually modify and control the farm climate
by, not only, reducing wind speed but also by creating changes in the
microclimate within a paddock.
Microclimate is the climate near the ground, in which animals and plants
live and, by effecting this, shelter can bring changes that benefit
both stock and crops.
The On-Farm Benefits of Timberbelts
Protection of Crops
and Pasture:
Strong winds can reduce plant growth by increasing
evaporation from plants and soil, making them more susceptible to
moisture stress problems.
Strong wind will also damage plants by causing sand blasting, leaf
rubbing or stripping and tearing of leaves.
By reducing all of these factors timberbelts can improve stock and
crop yields.
Decreasing Wind Erosion:
Timberbelts will lower wind speeds to a level where soil erosion is
minimised.
The introduction of deep rooted perennial plants also assists in
estabilising the soil on these areas.
Protection of livestock:
Extremes of temperature create
inefficient growing conditions for livestock as animals will be
required to use extra energy just to maintain basic metabolic
processes.
This reduces the energy available for increasing body weight or
producing milk or wool.
Timber Production:
By planting a multi row timberbelt including commercial timber
species, a timberbelt can be managed to produce on- farm timbers
and high value clearwood for sale.
Nature Conservation:
By using a diverse range of species a timberbelt can provide habitat
for a range of native bird and animal species.
The value to wildlife can also be increased by designing the timberbelt
to link any native remnants on the farm and act as a wildlife
corridor between them.
Lessening the Danger of Grass Fire:
By reducing the wind speed a timberbelt has the potential to slow the
rate at which a fire can spread, thus making it easier to control.
Designing a Timberbelt to Capture Multiple Benefits
of Shelter, Timber Production and Nature Conservation.
Two Rows
Three Rows
Four Rows
The following suggestions for design, taken from
Farm Forestry Clearwood Production, include both
shelter and timber trees.
The shelter rows ensure that one or more rows of trees will be retained
for shelter and nature conservation after the timber trees have been
removed from the other rows.
Following harvest, the timber species can be reestablished while the
structure and conservation benefits of the shelterbelt remain
intact.
Remember these designs are suggestions only, they can be adapted to
suit individual situations or new designs created to fit in your
farm.
Two Rows
Timber and shelter trees planted at even spacing in
separate rows.
With this model you would plant all trees at 2m spacing
The shelter row would be left as such and the timber species could be
selectively thinned by year 6 to leave the best stems for clearwood
production.
This would mean that the timber trees would be left at a final spacing
of 4m to maturity (250 trees/km).
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SPACING BETWEEN ROWS 2- 3m
Timber planted in clumps of 3 in one row and shelter trees
planted at even 2m spacing in the other row.
With this model the shelterbelt would be retained at 2m spacing while
the timber trees would be thinned to the best tree per clump for
clearwood production.
This would leave the timber trees at an average spacing of 4m (250
trees/km).
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1m WITHIN CLUMP, 2m BETWEEN CLUMPS
Three Rows
One row of shelter species evenly spaced at 2m,
Two rows of timber trees in clumps of 3.
The row of shelter trees would remain at 2m spacing with
the timber trees being thinned by about year 6 to one tree per
clump (500 trees/km), depending on form.
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1m SPACING WITHIN CLUMP, 3- 4m BETWEEN ROWS
Timber trees planted in clumps of three with shelter species
planted between clumps.
The shelter trees are planted in 2m gaps between clumps.
Within clumps timber trees are planted at 1m.
Timber trees will be then thinned to one tree per clump leaving an
average 4m spacing within the remaining timber trees (750 trees/km).
This model could also be used planting 2 trees per clump.
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SPACING BETWEEN ROWS 3- 4m
Four Rows
Timber and tall shelter trees planted alternatively at 2m spacing in
three rows with one row of shrub species on the outside.
No thinning of timber trees occurs in this model, all
timber trees are form pruned, but only those with good form go on
to be pruned (750 trees/km).
Shelter trees in the timber row can be selected and cut for
firewood.
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3- 4m BETWEEN ROWS
Species Selection
The first thing to do when planting a shelterbelt is to identify its
purpose.
Is it for protection of stock and crops, for habitat values, timber
production or to capture all these benefits?
Choice of species will come once this has been decided as you will then
pick a range of species to attract birds or produce timber, provide
dense or permeable shelter etc.
Timber Species Suitable for an Exposed Site:
|
|
| Botanical Name | Common Name | Timber Uses |
| Acacia melanoxylon |
Blackwood |
cabinet |
| Eucalyptus andrewsii |
New England Blackbutt |
sawlog |
| Eucalyptus dalrympleana |
Mountain Gum |
sawlog |
| Eucalyptus dorrigoensis |
Dorrigo White Gum |
pulp |
| Eucalyptus fastigata |
Brown Barrel |
sawlog |
| Eucalyptus nitens |
Shining Gum |
> sawlog, pulp, veneer |
| Eucalyptus nobilis |
White Gum |
sawlog, pulp, veneer |
| Eucalyptus saligna |
Blue Gum |
sawlog, cabinet, fuel, veneer |
| Eucalyptus viminalis |
Manna Gum |
sawlog, pulp, fuel |
| Grevillea robusta |
Silky Oak |
cabinet, veneer |
Shrub and Shelter Species Suitable for an Exposed Site:
Factors to Consider when Designing a Shelterbelt
Height:
The higher the
timberbelt the greater the area that will be protected.
A timberbelt can reduce wind speed up to 25 times the height of its
trees on level ground with the maximum benefit being in the zone 5 to
15 times the tree height away from the timberbelt.
Length:
Because wind swirls around the end of a timberbelt,
it is best to make the belt as long as possible.
If a timberbelt is too short the wind will be deflected around it at
increased velocity.
A minimum length of 200m is recommended with few gaps as these can
concentrate and funnel winds.
Permeability:
The permeability of a timberbelt affects both
the degree and extent of shelter.
A permeable timberbelt is most suited to provide general protection in
a paddock as, even though they let wind filter through them, they
provide a larger zone of protection than dense timberbelts.
Dense timberbelts are best when you want a small area of high quality
shelter as they block wind and create a greater reduction in wind
speed.
However, this reduction is restricted to a narrow zone and may also
cause more turbulence down wind.
Tree species and the number of rows will both effect the permeability
of a timberbelt.
Orientation:
Firstly it is important to identify which
winds do the most damage and locate timberbelts at right angles
to these.
The placement of timberbelts can be assisted by observing stock and
their movements in times of extreme weather conditions.
A straight timberbelt will generally only provide good protection
from winds at right angles to it.
It is good to consider, in relation to this, establishing a network
of timberbelts that might meet at right angles to maintain shelter
as the wind shifts.
Number of Rows:
Single row timberbelts are often not
desirable as any death which occur within the timberbelt will create
a gap leading to wind funneling.
Multiple row timberbelts on the other hand, allow you to use tall
trees with lower shrubby species.
Generally the effectiveness of a timberbelt will increase as the number
of rows increases from one to five.
Multiple rows can also provide permeability and height by using one or
two rows of tall trees.
By including shrub species in one of the rows the habitat advantages
of the timberbelt are also increased.
Suggested further reading: A Haven From Storm and Drought (GA
Ltd, RIRDC & LWRDC 1997).
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