Shelterbelt Primer

What is a shelterbelt?

A shelterbelt is a row of trees and/or shrubs planted in order to protect an area from natural elements such as wind and snow, or for other purposes such as aesthetics, carbon sequestration, and wildlife habitat. 

Image 1. A mature caragana shelterbelt (centre right) and another shelterbelt in the distance (centre left).
Source: Colin Laroque

There are different types of shelterbelts and different purposes for each. These types include:

  • Farmyard shelterbelts
    • Farmyard shelterbelts are placed in or around a farmyard. They are often planted for wind protection and/or to control blowing snow. They can also insulate the yard and protect gardens. They can provide habitat for wildlife, sequester carbon, reduce dust, provide privacy and beautify the area. 
    • Applicable species include caragana, chokecherry, hawthorn, red-osier dogwood, sea buckthorn, silver buffaloberry, villosa lilac, bur oak, green ash, hybrid poplar, Manitoba maple, Siberian crabapple, acute willow, silverleaf willow, Siberian larch, Scots pine, Colorado spruce, and white spruce. 
  • Field shelterbelts (fieldbelts)
    • Fieldbelts are planted in fields/agricultural land. Their main use is for wind protection for both soils and crops. They can also help with snow aaccumulation and increase the efficiency of irrigation. 
    • Applicable species include caragana, hawthorn, sea buckthorn, villosa lilac, bur oak, green ash, acute willow, silverleaf willow, possibly Siberian larch, Scots pine, occasionally chokecherry, Colorado spruce (multiple row only) and white spruce (multiple row only). 
  • Dugout shelterbelts
    • Shelterbelts planted around dugouts are valuable for protecting the surrounding area from snowmelt and spring runoff, and trapping this water into a dugout area. The water stored in a dugout with the help of a surrounding shelterbelt can be a valuable source of water for agricultural activities. 
    • Species applicable include caragana, hawthorn, sea buckthorn, villosa lilac, bur oak, green ash, acute willow, silverleaf willow, possibly Siberian larch, Scots pine, and chokecherry.
  • Roadside shelterbelts
    • Shelterbelts planted next to roads are generally used to protect the road from snow. They therefore reduce the need for road maintenance during the winter, reduce road dust from reaching crops, animals, or farmhouses and can also provide privacy.
    • Species applicable include caragana, hawthorn, red-osier dogwood, sea buckthorn and villosa lilac. 
  • Livestock shelterbelts
    • Planting shelterbelts along livestock areas is beneficial for the animals. They protect them from wind and dust and snow, improves animal health, provides shade and increase efficiency of feeding. Decreased animal stress can result in increased yields of goods such as milk and eggs. Livestock shelterbelts also benefit nearby people in that they protect from livestock noise and odours. 
    • Species applicable include caragana, chokecherry, sea buckthorn, villosa lilac, bur oak, hybrid poplar, Manitoba maple, trembling aspen, acute willow, silverleaf willow, Siberian larch, Scots pine, Colorado spruce and white spruce. 
  • Wildlife planting shelterbelts
    • Shelterbelts can be planted to provide areas for animal feeding, nesting, breeding, etc. They can also provide shelter from weather and predators, as well as provide a food supply. In return, these animals, such as birds, can provide pollination and help maintain a fruitful and healthy plant area. 
    • Multiple plant species can be planted in order to provide services for many different wildlife species. Native plants are also very recommended for wildlife plantings since they are already adapted to the climate and soil conditions of the area. 
    • Species applicable include chokecherry, hawthorn, hedge rose, red elder, red-osier dogwood, sea buckthorn, silver buffaloberry, snowberry, villosa lilac, bur oak, cottonwood, green ash, hybrid poplar, Manitoba maple, pincherry, Siberian crabapple, trembling aspen, acute willow, peachleaf willow, silverleaf willow, Siberian larch, Scots pine, Colorado spruce and white spruce. 
  • Riparian buffer shelterbelts
    • Riparian buffer shelterbelts are put in place to divide and buffer the area between agricultural land and a body of water (i.e., wetlands, floodplains, rivers, streams, creeks, lakes, sloughs). Riparian buffers can overall stabilize the area and improve habitat in both aquatic and terrestrial environments. They can reduce erosion, protect sensitive wetland areas, absorb excess nutrients and sediment from both aquatic and terrestrial areas, supply cover for wildlife, and more.
    • These buffers also very importantly aid in prohibiting flood water from reaching the nearby crops and agricultural lands, by providing distance/elevation from flood waters, slowing water entering the drainage system, and more.
    • Species applicable include chokecherry, hawthorn, hedge rose, red elder, red-osier dogwood, snowberry, cottonwood, possibly hybrid poplar, Manitoba maple, pincherry, trembling aspen and peachleaf willow. 
  • Forest shelterbelts
    • A forest belt is essentially a large field shelterbelt. To be considered a forest belt, a field shelterbelt must have at least 3 rows of trees and/or shrubs. The difference is they create a forest environment when the tree canopies of each row combine and close together. 
    • Forest shelterbelts also, therefore, provide the same services and serve the same purposes as field shelterbelts. However, forest shelterbelts are special in that they can potentially provide these services at a greater level, since there are fewer gaps in the canopy.
    • Species applicable include the same species as for fieldbelts (see above).

Shelterbelt characteristics affect the effectiveness and capabilities of your shelterbelt. Important characteristics include:

  • Effect of height
    • The height of your shelterbelt determines how much of the downwind land area will be protected by it. Height of course varies with each shelterbelt. Shelterbelts also change and increase height over time as the trees continue to grow.
  • Effect of density
    • Naturally, a denser shelterbelt will allow less wind to pass through. This increases the size of the protected area.
    • Shelterbelt density, flow patterns and areas of protection can be altered by the number of rows planted, distance between each tree and species used. For example, increasing the number of rows or decreasing the distance between each tree increases shelterbelt density and provides a more solid barrier. Species used will also decide the shelterbelt height, density, and influences the distance of the protected area.
  • Effect of orientation
    • Shelterbelts are most effective when they are positioned at right angles (i.e., perpendicular) to coming winds. In the prairies the wind often comes from the north and west, so shelterbelts should be positioned perpendicular to those directions. 
    • The purpose of the shelterbelt can also decide the orientation of the shelterbelt. For example, farmyards and feedlots often require protection from cold winds, dust or blowing snow to protect the farm animals. Due to this, these shelterbelts could be planted to protect from multiple directions.
  • Effect of length
    • The length of the shelterbelt determines the amount of area to be protected. The height of the shelterbelt determines the extent of the downwind protection. To maximize the efficiency of your shelterbelt, the length should be at least 10 times the height. 

Microclimate modifications

In and around the protected zone of a shelterbelt is a different microclimate than the surrounding area. The lesser amount of wind in this area often results in a changed microclimate; temperature and humidity levels often increase which can result in decreased evaporation and therefore water loss from transpiration. This means the plants have to use less water (i.e., plants are more water-efficient). It can also allow earlier crop planting. However, the increase in humidity and temperature could also potentially lead to an increased chance of disease, such as mildew. Lower humidity and temperature along with shading could also result in a slower rate of snow melt, making fields difficult to access in the spring, which is something to be aware of as well. 

Image 2. An example of an understory/microclimate area of a coniferous multiple-row shelterbelt.
Source: Colin Laroque

References

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