Shelterbelt Primer

Planning

Perhaps the most important step in shelterbelt planning is doing research and choosing plants that are suitable to successfully grow in your geographic location. 

Another part of planning your shelterbelt is which shelterbelt design you will select, and the equipment needed to prepare and create such a design.

  • As you plan your shelterbelt, keep the following considerations in mind:
    • Locate your shelterbelt where it will be most effective at its purpose
    • Design the shelterbelt to meet your goals with the available space
    • Choose suitable plants (as mentioned above)
    • Prepare the site before planting any shelterbelt species 
    • Arrange means for labour
    • Provide a nursery or simply care and protection for the seedlings until time for planting
    • Means to control weeds before and after the planting stage

During the planning stage, the potential site for a shelterbelt should be assessed. Identify your concerns of the area and decide on the areas of necessary change or improvement that a shelterbelt could aid in. You should also assess your environment in the area and be sure that it can withstand the addition of a shelterbelt. For example, soils low in nutrients might not be able to cope with additions of large plants such as trees. These issues should be taken into consideration before a shelterbelt is implemented. 

Potential uses/objectives of a shelterbelt include: 

  • Reduction of soil erosion, wind disturbance, snow drift and buildup, odour, noise to or from surrounding areas, net greenhouse gas emissions and dust volume. Further objectives include insulating buildings and reducing energy consumption and costs, protecting, shading and insulating livestock from weather, aesthetics and beautification of the area, providing wildlife habitat and increasing biodiversity of the area, visual screening, capturing atmospheric carbon and increasing property value. 

After implementing and monitoring your shelterbelt for a period of time, modifications can be made in areas that you deem necessary. For example, things such as weed management or pruning methods can be altered. Objectives also can be modified or additional ones can arise. Priorities may have even changed altogether. 

Shelterbelt design

There are several types of trees and shrubs that can be used in a shelterbelt for various purposes. Different plant species have different growth times as well as characteristics such as height, density and longevity which all play a role in creating a successful shelterbelt. 

  • Height
    • Shelterbelt height of course influences the area that the shelterbelt will affect. With a taller shelterbelt, more area is protected. 
  • Growth times and longevity
    • If you want your shelterbelt to come into effect quickly, decide on fast-growing tree and shrub species. Fast-growing species are often also short-lived so slower-growing trees can be planted alongside them to equal this out. 
  • Density
    • Tree and shrub density influences wind protection. If you have a denser tree cover, less wind will penetrate through the shelterbelt. 
    • Shrub species protect the area closer to the ground surface. 
    • Coniferous trees with dense, year-round foliage can greatly help protect the surrounding area from wind and snow. In contrast, deciduous trees and shrubs lose their foliage in the fall so during the cold months deciduous shelterbelts are less effective.
  • Tree age
    • Younger trees also protect the area closer to the ground surface. Older trees protect the area higher above the ground surface. 
  • Tree placement
    • Shelterbelts are very effective with five rows of tree and shrub species. If there is not adequate space for five rows, it is better to plant less rows, such as three, instead of crowding more rows in a tight space. One must allow full growth of a shelterbelt for it to be most effective so crowding is never recommended. If three rows would even seem to be too tightly crowded, a two-row shelterbelt is an appropriate alternative for such a crowded area. It is even better if the trees in each row are staggered from the other row. This allows for optimal protection. Conifers are recommended for these two or three row shelterbelts. Single row shelterbelts are also appropriate for certain projects, such as when a shelterbelt is planted on arable land.

It is normally recommended to plant various plant species in a shelterbelt to promote diversity. Diversity is beneficial in all natural environments including shelterbelts. More benefits and services are provided by multiple species of tree and shrub. There is also less of a chance of a massive loss of biomass from events such as disease, insect infestation, fire or drought. This is because different species react differently and have different adaptations to withstand such events. 

Which trees and shrubs to select for your shelterbelt mainly depend on the climate of the area and the purpose of the shelterbelt.

Shelterbelt design – soil zones

You also want to focus on species that can thrive in your local soil zone. Soil zones are large geographical areas where one soil type dominates. In Saskatchewan specifically, there are 4 soil zones: Brown, Dark Brown, Black and Grey. Different plant species survive better in different soil zones because soil zones have different characteristics regarding soil moisture, nutrient regime, pH, climate, etc. 

The Brown soil zone in southern Saskatchewan covers the Mixed Grassland Ecoregion of the larger Prairie Ecozone. This ecoregion area is the most arid area in Saskatchewan. This means that drought tolerant plants will do well here. The dominant vegetation in this area is grasses. Large trees and forest areas that require vast amounts of water do not thrive here like in other areas, but they can be successfully planted in shelterbelts if they are monitored and watered sufficiently. 

  • Caragana (Caragana aborescens) is a drought-tolerant shrub very suitable for the Brown soil zone. Of the woodland areas that are present, trembling aspen and shrub species are popular. Other species present include choke cherry, hawthorn, silver buffaloberry, northern snowberry, common lilac, eastern cottonwood, green ash, balsam poplar, Alaska willow and white spruce. 

Next, the Dark Brown soil zone around Saskatoon and down towards the Regina area covers the Moist Mixed Grassland Ecoregion of the Prairie Ecozone. This Ecoregion is still characterized by the gross Prairie Ecozone characteristics, but has a more subhumid continental climate and an increased amount of woodland area, among other differences. 

  • Species that thrive in this soil zone include choke cherry, hawthorn, silver buffaloberry, northern snowberry, eastern cottonwood, green ash, and peachleaf willow. Caragana is also applicable to this soil zone. 

The Black soil zone found more north, near Prince Albert and down towards Yorkton, covers the Aspen Parkland Ecoregion of the Prairie Ecozone and the Boreal Transition Ecoregion of the Boreal Plain Ecozone. This area is overall a mix of farmland and forest with many deciduous species. This area is considered to have a humid continental climate.

  • Trembling aspen and understory shrubbery are prominent in the Aspen Parkland area. Species in the Boreal Transition area include many aspen and white spruce along with some jack pine, black spruce and balsam poplar. More species include red-osier dogwood, chokecherry, Saskatoon berry, snowberry, bur oak, and willow. 

Finally, the Grey soil zone of Saskatchewan is found mainly in the Boreal Transition and the Mid-Boreal Upland Ecoregions of the Boreal Plain Ecozone. This geographical area is the most north of all mentioned. The higher precipitation level present in this area means that greater biomass can be supported; therefore, this is the most forested of the areas mentioned.

  • Species to be planted in shelterbelts in this area should be able to withstand lower temperatures and higher precipitation levels. Species that thrive in the Boreal Transition area include trembling aspen, balsam poplar, white spruce, balsam fir, willow, some black spruce and tamarack.

Shelterbelt tree and shrub spacing

  • There are different spacing recommendations within shelterbelts for different species of tree and shrub. 
  • As a rule of thumb: 
    • Deciduous trees are planted 2-5 meters apart
    • Coniferous (evergreen) species are planted 2-3 meters apart 
    • Hybrid poplars, hybrid larches, poplars or spruces are planted 2 meters apart
    • Shrubs are planted 1-2 meters apart
    • Keep in mind these are general recommendations and spacing can vary with different shelterbelt purposes, species used, planting site conditions, etc. 

Space required for shelterbelts in crop areas can be reduced by planting only a single row shelterbelt. However, the spacing between plants in the single row should be adequate.

Further planning actions include:

  • Choosing the shelterbelt area
  • Preparing the shelterbelt area (e.g., removing weeds, amending the soil)
  • Digging the planting holes

References

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