Shelterbelt maintenance and management

Shelterbelts can provide a range of benefits over a long period of time if they are managed appropriately.

Management aims to maintain the:

• health and vigour of individual trees and shrubs
• overall structure of the shelterbelt as an effective barrier to the wind.

Your management practices will usually involve the following:

• weed control
• pest animal control
• pruning
• insect and disease control.

The level of management required to maintain a belt will often decrease as the belt becomes established.

Newly established belts

Newly established belts are usually the most vulnerable, as they are highly susceptible to:

• grazing by animals
• dry conditions
• weed competition.

Soil moisture helps young plants to establish

Thorough site preparation and weed control can maximise the amount of moisture available to young plants. Good soil moisture during the first growing season ensures good root and above ground growth.

Faster growth reduces the plant's susceptibility to grazing, fire, insect attack and weed competition. This in turn leads to higher rates of survival.

Replace dead plants early

Losses of plants are likely to be highest during the first few years. Dead plants should be replaced as soon as possible to maintain even heights and densities within a belt.

It's harder to establish new plants in an advanced belt due to competition for water and shading by the older plants.

Weed control

Grasses and weeds compete with shelterbelt plants for water, light, space and nutrients.

Weeds can significantly reduce the effectiveness of a belt and degrade the quality of the habitat for local wildlife. Strategic grazing, herbicide application or possibly burning can be used to control weeds.

Young belts

Effective weed control is especially important during the first 5 years. A shelterbelt that has effective weed control from establishment on will become effective earlier and last longer.

Weed control should be undertaken within and between the rows of a shelterbelt to give plants the opportunity to establish. Weed control is undertaken between rows to remove the source of weed seeds. This can be achieved by mowing weed species prior to them setting seed.

Complete removal of the weeds is more appropriate in dry areas.

Older plantings

It's recommended that weed control be undertaken for up to 10 years following the establishment of a belt. After this time you can do it as required to ensure that no serious weed infestations occur.

Weeds that aren't controlled can spread weed seeds to other areas of the property.

As a belt matures weed control should become less time consuming. Litter from the trees and shrubs will fall and create a mulched area. Weeds will find it more difficult to get sufficient sunlight and moisture to become established.

Protection from animals

A range of animals, both domestic and wild, can damage both new and old shelterbelts.

Closely monitor your shelterbelt so you can quickly address any issues.

Stock accessing the shelterbelt

Stock within a well-established belt can damage or reduce the health of belt species by:

• grazing on shelter plantings
• leaning on fences to graze
• trampling and compacting the soil
• increasing nutrient levels within the site
• rubbing and chewing on the trunks of plants
• preventing the regeneration of new plants within the belt.

All shelterbelts located in areas where they may be grazed should be fenced to ensure grazing can be controlled. Grazing may be used for short periods to reduce the fire risk. Some belts benefit from crash grazing to promote bushiness.

Pest animals accessing the shelterbelt

Rabbits, hares and other grazing animals can also enter a belt and cause significant damage to both plants and local wildlife within the belt.

Rabbits can degrade the habitat value of a shelterbelt by grazing and eliminating understorey species.

Foxes and feral cats must be controlled or they will predate on wildlife within a shelterbelt. Nest predation in linear strips of vegetation is almost double that of large areas of remnant vegetation.

Pruning

Pruning a shelterbelt may reduce its potential to deflect wind by reducing its density or creating gaps. Carefully consider the purpose before undertaking pruning.

Damaged or dead branches may be removed if their removal is not likely to alter the density or profile of the belt. You can do this annually to enhance the shape, density and longevity of a belt.

Always use appropriate equipment. A clean cut out from the main stem is ideal, as it will reduce the chance of infection of the tree. If there's the possibility of trees having a disease, the pruning equipment should be sterilised between each use to prevent infection of subsequently pruned trees.

Pruning may be an integral part of the management of shelterbelts for the production of timber products such as saw logs.

Contact us for advice on techniques for pruning timber species.

Structural management

The overall structure of a shelterbelt determines its effectiveness. Therefore structural management should take into consideration the ideal cross sectional profile, height and density of a belt.

As trees grow, the relationships among them change. The density and position of tree crowns alter in relation to height above ground and neighbouring trees. These changes are usually small but they may sometimes alter the belt to such a degree that it doesn't provide as much protection from wind as it should.

An example of this is where a belt may be a higher density than desired. High-density belts don't protect as large an area as medium density belts.

Altering the structure of a belt can be difficult. It is important to keep in mind what you want and need the belt to do. See Effective Shelterbelt design for more information.

Increasing density

A shelterbelt with a density lower than desired can be improved through inter-planting within the belt.

Another method for increasing the density of an aged or low-density shelterbelt is felling trees close to the ground to create coppice (regrowth) from the tree stump. Multiple stems re-grow from the stump, creating a denser stand of vegetation. Tree removal can also promote regeneration of new plants.

The shelter provided by coppice is lower than that provided by mature Eucalypt species. Some trees may not re-grow after felling. This technique is only appropriate for certain species.

Further references

Bird, P.R. (2000) Farm Forestry in Southern Australia, Pastoral and Veterinary Institute Hamilton, Centre State Printing

Burke, S. (1998) Shelterbelts

Acknowledgements

Dr James Brandle from University of Nebraska for the information and support for the preparation of this page.