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Shelterbelt Design Gets An Update

Here’s a great winter project if you are planning to establish treed shelterbelts around winter grazing sites or rejuvenate old shelterbelts around the yard and fields.

Agriculture and Agri-Food Canada’s Agroforestry Development Centre at Indian Head, Sask. has developed a new design for low-maintenance shelterbelts modelled after natural bluffs. The eco-buffers are created with three to five linear rows of numerous species of trees and shrubs planted in a narrow, dense arrangement.

Agroforestry specialist Laura Poppy says the goal is to develop a system with a concentrated group of plants that will be diverse and establish quickly. Findings from the research site at Indian Head and a new demonstration planting in 2009 at the Western Beef Development Centre near Lanigan, Sask., suggest usual maintenance of weed control and watering is required for the first one to three years. Then you can let Mother Nature take her course.

A five-row eco-buffer one-half mile long and eight metres wide requires about 4,000 trees and shrubs. It should include a minimum of four species of shrubs and at least two tall, long-lived species of trees. Regardless of the species, the plants are planted one metre apart in the rows, and the rows are set two metres apart.

Contrary to the old school of thought, increased competition from close spacings doesn’t harm the establishment or growth of trees and shrubs, Poppy says. Buffers at Indian Head site have shown a tenfold increase in species within five years. This is attributed to the use of suckering species within the planting.

For functionality and interest, Poppy suggests choosing a variety of species that are native to your region and adapted to the planting site. Carragana is not native to the Canadian Prairie and not recommended for use in the eco-buffer system. Select trees and shrubs with diverse characteristics — thorny, suckering, tall, short, fruit bearing, fast and slow growing. A range of heights will give the buffer a natural, layered appearance.

There are really only two rules of thumb for the arrangement: the short shrubs should be to the outer sides of the shelterbelt and every sixth plant should be a long-lived tree.

The selection for the WBDC’s ecobuffer included varieties suited to the aspen parkland eco-region. The small shrubs included snowberry, wood’s rose and potentilla. Those were interspersed with the taller shrubs — red osier dogwood and buffalo berry — in the outer rows. Pin cherry and chokecherry, which are taller shrubs, were planted in the three inner rows. Saskatoons were sprinkled throughout the planting. Balsam poplar and trembling aspen were chosen for the nurse trees to be planted sparsely in the outer rows and throughout the inner rows. Every sixth tree in the three inside rows is a long-lived species, either green ash, Manitoba maple or white spruce. Native willows were placed where the shelterbelt runs through low areas of the field.

Functions of a shelterbelt

This alternative design, developed from a combination of systems found in Denmark and North Dakota, will function as well as the traditional Prairie shelterbelts to conserve soil and water, manage snow, and protect, yards, crops and livestock from wind, while providing wildlife habitat.

The advantage over the traditional design is that an eco-buffer enhances biodiversity to a greater extent, Poppy explains. Connected to natural areas, such as a riparian zone, wildlife corridor or wooded area it can have an even greater benefit for conservation and as a wildlife habitat.

As is the case with traditional shelterbelts established to protect livestock areas, it is very important to always protect the planting with a fence to keep the livestock out. Cattle compact the soil and physically damage the trees and shrubs, which leads to a decline in the health and growth of the stand. There is an agroforestry system called silvopasture, which integrates livestock, trees and forages for the benefit of all, however, it is a very detailed system that requires careful management to ensure the productivity of all components.

With some management, eco-buffers could mature to become a valuable source of wood and fruits. Left on their own, the trees and shrubs will naturally regenerate through the years. Similar to multi-species pastures, the mix should maintain a synergistic balance when the best-adapted species are chosen. Human intervention, such as extensive use of herbicides or pesticides that damage the trees and shrubs, will upset the balance and result in a decline of species.

The Prairie Shelterbelt Program has been ongoing since 1901 offering technical services and seedlings free of charge to eligible rural landowners to encourage environmental stewardship and beneficial management practices. Applications are accepted from June 1 the year prior to delivery, to March 15 for delivery in the spring to numerous points in Manitoba, Saskatchewan, Alberta and the Peace River area of B.C.

For details, or call 1-866-766-2284.

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