A shelterbelt's main function is to reduce wind velocities and affect wind currents. Some of the benefits from controlling wind in and around farmyards are: reduced snow removal costs by controlling blowing snow, building protection, decreased energy consumption, increased water supplies by trapping snow for dugouts, creation of microclimate conditions and protection for gardens. Other advantages include wildlife habitat enhancement, carbon sequestration, reduced dust, privacy, beautification and creation of a nicer environment to live and work in.
Location and shape
A shelterbelt should be positioned perpendicular to prevailing winds and located approximately 30 metres (m) away from buildings or other structures in order to allow drifting snow to accumulate on the leeward edge of the shelterbelt. This distance allows the trees to provide excellent protection when they reach a height of 15 m. For optimum benefits, plan your shelterbelt so that buildings are located in the maximum wind-speed reduction zone, i.e. from two to seven times the height of the shelterbelt.
Future yard expansion, overhead lines, buried lines should be taken into consideration when selecting a planting location.
Older shelterbelts should be maintained and removed only if necessary. In most cases, an aging shelterbelt continues to provide adequate wind and snow protection, but it may be no longer aesthetically pleasing. Older shelterbelts were planned for the farm practices and needs at the time of planting. With changing and expanding farm operations more space within the yard site may be needed for additional buildings and equipment storage. Plan and prepare a new shelterbelt site further out from the existing trees. When the new shelterbelt begins to provide the benefits you need, you can consider removing the old shelterbelt if it is beyond restoration.
Prevailing winds in winter are usually from the north and northwest. Therefore shelterbelts should be located along the north and west sides of the farmyard. The effective protection zone extends from a distance out to seven times the height of the trees. Drifting snow varies with the direction and velocity of the wind, the type of snow, the fetch distance and the composition of the shelterbelt. However, snow often piles up on the windward side of the shelterbelt at distances one to three times the height of the trees.
An additional snowtrap row could be planted 15-30 m from the windward side of the shelterbelt to reduce the effect of excessive snow accumulations within the primary shelterbelt.
Do not plant shelterbelts close to your home or other buildings. Trees planted too close will cause snow to drift into areas that should be snow-free. Plant shelterbelts for winter protection at least 3 m from farm buildings that are on level land.
Remember, shelterbelts may create snow problems when planted too close to buildings or roads. If the purpose of the shelterbelt is to trap snow, then your planting should be located 30-90 m away from existing or proposed buildings or roads. Keep in mind that shrubs create short and deep snow drifts whereas deciduous trees create longer and shallower drifts.
Certain situations like steep slopes, low areas, farm access roads or municipal regulations may not allow planting shelterbelts the recommended distance away from your yard. In these cases reduce the number of rows and plant high density shelterbelts. If your land slopes steeply downward on the north or west side of your farmyard, consider planting closer to the farmyard than the traditional recommended distances. However, do not plant closer than 18 m from main buildings or driveways if snow drifting is a concern.
Shelterbelts planted closer than recommended may cause snow problems around buildings and roads especially during heavy snowfalls and severe winds.
If your farmyard is located close to a public road with insufficient space to plant a shelterbelt, you may want to try establishing a shelterbelt across the road. Remember to follow municipal or highway regulations regarding new plantings next to roads. If you must plant across the road from buildings, recognize that drifting snow may block the road.
Because wind and snow whip around the ends of a wind barrier, the ends of the shelterbelt should be extended approximately 15 m. beyond each corner of the area to be protected. Shelterbelts do not have to be planted in rigid, straight lines. A curved shelterbelt on a natural topographical contour line around the north and west sides of your farmyard will look more pleasing.
Shelterbelts can follow the contour of a valley or creek, run in an angle, or even have a circular shape around the yard site. The main consideration is to keep the spacing parallel between rows for ease of between-row cultivation and maintenance.
Shelterbelts can be planted to control hot, dry summer winds. Prevailing winds in the summer are generally from the south and southwest. Shelterbelts should therefore be located along the south and west sides of the area to be protected.
A well-designed shelterbelt reduces wind velocity but still allows a breeze for ventilation. If a shelterbelt is planted without allowing air flow for ventilation, the summer conditions within the farmyard may be uncomfortably hot. Shelterbelts planted for summer wind protection usually consist of one or two rows of trees located to the south and west of the farmyard. A one-row shelterbelt may be composed of either deciduous or coniferous trees. The outside row of a two row shelterbelt (i.e. southward) usually consist of deciduous shrubs or small deciduous trees, and the inside-row, of moderate to tall deciduous trees.
Do not plant shelterbelts across old feedlots, near manure piles or across barnyard drainage ways. Trees, particularly conifers, will perform poorly in such locations if they even establish.
Also, when soils or drainage conditions change drastically, it may be necessary to correct the drainage or change the species of trees and shrubs in the shelterbelt to match the new site conditions.
Plan for future yard expansion, whether for buildings, grain storage and handling, equipment parking area, livestock feed storage, corrals, or a new dugout. Other important location considerations include buried electrical, phone, gas, water and sewer lines; overhead electrical lines; and topography.
Avoid field access openings in shelterbelts to the west and north sides of the yard. If you must have an opening to these directions, stagger the shelterbelt planting to reduce the wind tunnel effect. If it is necessary to cross field roads, driveways or large ditches with a shelterbelt, avoid creating wind tunnels by making the crossings at an angle.
Check with your municipal, county or district office or with the Provincial Highways Department on set back distance regulations for the allowable minimum distance between a shelterbelt and the main road or highway. In most municipalities, set backs range from 40-45 m from the centre of the main road and 90 m from the highway right of way. In some cases, written permission may be obtained for using a smaller set back.
Determining the number of rows to plant
The farmyard shelterbelt should consist of a combination of tall, fast-growing, long-lived and dense trees and shrubs. Of course no one tree or shrub has all these characteristics. However, by combining a variety of species, each having one or more of the desired characteristics, you can create a multi-functional shelterbelt.
Your knowledge of how the density, height and length of a shelterbelt affects wind, will play an important role in helping you design your planting plan. Five shelterbelt rows are recommended on the north and west sides of the yard to provide protection from prevailing winds. Two or three rows are usually adequate on the east and south sides. Prevailing wind directions vary from season to season, and according to your location on the prairies. This may require you to establish a denser shelterbelt on other sides of the yard than the north or west.
In winter, winds from north to west directions bring in the colder temperatures, while southerly winds seem to bring in milder temperatures usually with snow. Winds are usually strong creating high wind chill factors and typically blow freshly fallen snow around buildings and onto roads. If this is the case for you, plan for at least three or more rows of trees and shrubs in those areas of the yard. Keeping in mind the hot summer months when temperatures can reach into high 30 degree Celsius range, air flow through the yard is necessary to achieve a comfortable temperature for your living space. Review your particular situations and address your needs accordingly.
Certain attributes of the yard may not allow you to plan for the recommended shelterbelt but wherever possible, a multi-row planting will provide better benefits. A minimum of three rows, using a combination of deciduous shrubs, trees and conifers are needed to provide proper wind reductions. The number of shelterbelt rows that you have room for plays an important role in species selection.
Some circumstances may not allow for a full five-row shelterbelt, and rather than decrease the distance recommendations between rows, or plant the shelterbelt too close to buildings, reduce the number of shelterbelt rows as required. If you require protection that a properly designed five-row shelterbelt would give, but only have room for three rows, compromise by planting a dense shrub row to trap snow, a tall deciduous tree to lift the wind and a conifer row for added year-round protection.
Another option when working with limited space is to combine shrubs and tall deciduous trees in the same row to increase the sheltering benefit.
The shrub row or low dense species provides protection from ground level winds and act as the main snow trap. Selecting some fruit bearing shrubs provides additional wildlife habitat benefits. These rows should be planted on the windward side as an outer row to trap snow and to deflect the wind upwards.
Dense shrubs cause an accumulation of snow close to the belt which provides the inner tree-rows with the needed soil moisture for the growing season. Taller deciduous rows may lose their lower branch density and provide little or no protection at lower levels. However, their height and density in the upper canopy direct wind currents upward and reduces wind over a larger area on the leeward side of the shelterbelt.
It is important to only plant long-lived deciduous species in the central rows of the shelterbelt. Fast growing species like poplar tend to have a shorter lifespan especially if affected by poor moisture conditions. Removal in later years could pose a problem if planted between rows of other long-lived species. Therefore, ensure adequate distance is left between rows to facilitate removal later.
Five row shelterbelt
- Row 1 is a species of shrub.
- Sea Buckthorn
- Siberian Crab
- Row 2 and 3 are a species of tall deciduous.
- Row 4 and 5 are a species of coniferous.
- Colorado Spruce
- White Spruce
- Scotts Pine
Species can be planted either as a pure row or in some cases, a mixture of species can be planted within the same row.
Shelterbelts with fewer than 5 rows
- For two-row shelterbelt, use rows [1-2, 1-3, 2-3]
- For three-row shelterbelt, use species listed for rows [1-2-3, 1-2-(4/5), 1-3-(4/5), 2-3-(4/5)]
- For four-row shelterbelt, use species listed for [1-2-3-4, 2-3-4-5, 1-2-3-5, 1-3-4-5]
Spacing and arranging trees in shelterbelts
Some consideration should be given to spacing seedlings according to their estimated mature crown size. While it takes longer for trees to form an effective windbreak at wider spacing, this shortcoming can be overcome by staggering the trees in adjacent rows. The delay in effectiveness will be more than offset by the increased growth and vigour of the trees that have adequate space to grow. Well spaced trees live longer, retain their lower limbs better and produce more foliage.
|Tree and Shrub Species||Minimum Recommended
Tree and Shrub Species
Within-row Planting Distances
|Choke Cherry, Hawthorn, Hedge Rose, Pincherry, Red Elder, Red-osier Dogwood, Sea Buckthorn, Silver Buffaloberry, Snowberry, Villosa Lilac||1.0||3.0|
|Bur Oak, Cottonwood, Green Ash, Hybrid Poplar, Manitoba Maple, Siberian Larch, Trembling Aspen, Willow||2.5||8.0|
|Scots Pine, Spruce||3.5||12.0|
Shelterbelts with both deciduous and coniferous species must have adequate space. If deciduous and coniferous tree rows are planted too close together, the faster growing deciduous trees soon overtake the conifers in height. When this happens, the conifers become shaded resulting in deformed growth, stunting and reduced effectiveness.
To avoid problems, leave the recommended minimum 6 m spacing between rows of deciduous and coniferous species. All other between-row spacing should be 5 m Spacing within-row depends on the species.
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