Shelterbelt Life Phases

Overview

There are 3 main phases of a shelterbelt lifespan: the establishment, functional and mature phases. Establishment begins the year before planting with site preparation and continues for 5-10 years after planting and is when the seedling grows 3-5 meters tall. Next is the functional phase, when the shelterbelt canopy will close. The litter layer also begins to thoroughly form and there is abundant wildlife habitat. Pollinator species and crop yields are greatly benefitted at this more forest-like stage. Finally, the mature phase is when trees and shrubs are fully grown and continue to supply the same benefits and services as they did during the growing, functional phase. A mature shelterbelt environment is also continually more diverse than before. 

Establishment phase

  • Establishment begins the year before planting with site preparation and continues for 5-10 years after the shelterbelt has been planted, depending on species and growing conditions. Site preparation can include cultivation, herbicide application, weed removal, etc. A cleared and clean patch of soil is normally the goal of site preparation. 
  • The establishment phase is when a seedling grows to 3-5 meters in height. 
  • By the end of the establishment phase, some local wildlife will have created a habitat in the shelterbelt and area. Other plant species also start to emerge during the establishment phase due to animals carrying them in, seeds being dispersed in the area, etc. 
Image 1. Shelterbelt seedlings during the establishment phase.
Source: Colin Laroque

Functional phase

  • At the end of the establishment phase and the beginning of the functional phase, the canopy of the shelterbelt will begin to close/ the crown of the trees will begin to touch
    • This barrier gains height with shelterbelt age
    • Individual trees begin to compete with each other for light, space, nutrients, and moisture, such as in a typical forest area
      • Therefore, the plants with the best genetics will be able to compete best and will go on to continue growing. However, a shelterbelt is planted in order for all plants to have adequate space to succeed, so all trees have the potential to grow larger. Although this, they will still naturally vary in size. 
  • Shelterbelts have been seen to increase crop yields since they can regulate climate, light penetration and soil characteristics in the nearby areas. These regulations influence the understory of the area and this is where crops are included. 
  • At the functional phase, tree debris such as leaves and dead branches may fall and begin to contribute to the undergrowth litter layer. 
  • As well, the shelterbelt also begins to become a habitat for local wildlife. Birds can begin to forage and nest in the area, and some animals such as small mammals (e.g., rodents, rabbits) can begin to call the shelterbelt area their home. This means that ultimately these animal species also begin to be in competition with one another, similar to the trees and shrubs. These areas become hunting grounds for these animals, and even possibly humans, and this can continue to change the dynamic of the shelterbelt area. 
  • It has been seen that more pollinator species are present in these sheltered and protected shelterbelt areas than in adjacent open areas. This is beneficial especially for fieldbelts adjacent to crops and shelterbelts used for wildlife habitat and aesthetics, seeing as this enhanced pollination livens and brightens up the area and produces more herbaceous output (e.g., crop yield, flowers, etc.). 
  • Crop yield is also benefited by the protection of shelterbelts to the soil regarding wind and water erosion. The roots of the shelterbelts help keep the soil in place while also protecting the surface soil from aboveground environmental damage. Less erosion allows increased crop production (yield) and helps the area flourish overall.

Mature phase

  • When trees and shrubs fully grow and continue to age, they likely still continue to supply the same benefits and services to their environment as they did during the growing, functional phase. However, the struggle to provide these benefits begins if the trees become sick or their environment is particularly rough. Often an open agricultural field environment has less protection from stress than a natural forest environment, and this can lower the lifespan of a shelterbelt. 
  • A mature shelterbelt environment is also continually more diverse than before. As the trees and shrubs die, more trees/shrubs and/or new species can be planted in their place and this therefore increases diversity. As well, mature shelterbelts to be able to house additional species of animal and plant that have migrated to the shelterbelt area which also enhances diversity. 
Image 2. Mature shelterbelt trees.
Source: Colin Laroque

References