Silvopasture: Christmas Trees and Forage

Kootenay Tree Farms in partnership with the BC Hydro, the BC Ministry of Forests and Range and local ranchers are demonstrating the feasibility of using agroforestry to manage for Christmas tree production and enhanced forage availability in a low-intensity silvopasture system. The density and growth form of Christmas trees provide large areas for concurrent forage production (Figure 1). In the native-stand Christmas tree system employed by Kootenay Tree Farms, Douglas-fir (Pseudotsuga menziesii) are produced by stump culture; a new stem is grown from a lower branch remaining from the harvest of previous tree creating a perpetual renewal of trees from the same root system. Because the trees have fully established root systems they can take advantage of the nutrients applied at all stages of production. Fertilization therefore benefits the trees and can also increase growth of the grassy understory (Figure 2). The increased understory biomass however, can pose production problems for Christmas tree growers through tangling in the lower branches and creation of cover for small mammals that can damage the crop trees. Grazing therefore, not only benefits livestock production, it also controls the grassy biomass surrounding the trees (Figure 3), reducing potential negative impacts of a vigorous grass sward. Increased forage availability is also beneficial to wild ungulate species. There is a critical forage availability issue in the Kootenays with increasing pressure on Crown rangeland from an expanding ungulate population. In addition to the benefits to livestock and wildlife, silvopastoral systems on Crown land combining Christmas trees and forage production can increase the returns to the Crown 10 fold in comparison to forage only areas.

With support from the BC Agroforestry Industry Development Initiative this demonstration builds on observations that both tame and introduced grasses in the understory of Christmas trees appear to respond very favourably to fertilization of the trees. In order to quantify the additional forage gained through fertilization, trials are being established on two sites in the East Kootenay near Cranbrook. The first is located on a BC Hydro power transmission right-of-way and the second is located on Crown land in a designated Christmas tree permit area. Fertilization in addition to the normal tree pruning practices will be tested on areas of both a tame grass forage mixture and predominantly native pine grass (Calamagrostis rubescens) at the BC Hydro site. On the Christmas tree permit site, the effects of tree pruning and fertilization will be tested alone and in combination on a mixed stand of native and introduced forages. A second area at this site will test the effects of mature timber overstory removal. It is normal practice to harvest overstory trees while protecting the developing sapling understory as the subsequent Christmas tree crop. Enclosures will be placed in the stand pre- and post-harvest to assess forage response to management as a mature stand versus management as a Christmas tree production unit.

Kootenay Tree Farms is managing and delivering this project with co-operation from BC Ministry of Forests and Range staff who are providing forage enclosure cages, as well as assistance with drying and weighing forage samples. Annual harvest of the forage samples will be conducted with the co-operation of the two ranchers whose livestock will be grazing the sites. Local resource groups including the Kootenay Livestock Association and the Kootenay Christmas Tree Association have also shown a high degree of interest in the project and will promote the demonstration to their membership.

This project will not only quantify some of the production variables involved, but will also communicate the benefits of agroforestry industry, agency and stakeholder groups. Annual fall tours of the demonstration will be conducted to serve as an introduction to silvopasture management for Christmas tree and ranching industries, government agencies and other resource management groups. The tours will also communicate the findings of the trials and will build awareness of the concept of enhanced forage production through Christmas tree silvopasture. An extension note will also be developed incorporating the demonstration results for use by industry, resource agencies and other stakeholders to assist in decision making.

For more information on the Christmas tree silvopasture demonstration please contact Charlie Willis (kootenaytreefarms@shaw.ca).

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