Growing Birch Alongside Conifers Has Advantages

The body of research into the pros and cons of growing conifers among broadleaf trees in British Columbia's Interior Cedar Hemlock biogeoclimatic zone leads scientists to advocate for a new approach to regenerating forests.

Competing trees are an archrival of achieving free-growing status for conifers on logged sites.

At times, fast-growing broadleaf trees overtop young conifers, slowing the crop trees' growth through competition for light and water.

But paper birch also aids conifer growth and survival by transferring nutrients to seedlings and by subduing a lethal root rot fungus. Eliminating birch allows conifer saplings to grow faster, but more trees succumb to disease.

Researchers suggest that the prevalent aggressive and expensive treatments of removing competing trees and stumps infected with Armillaria root rot be applied only to conifer plantations on the most productive sites. For other areas, two new silvicultural approaches would be lower in cost, but require changing current reforestation requirements.

A widespread strategy would involve augmenting natural regeneration with planted conifers and treating only a few select areas with brushing or stumping. On the least productive or at inaccessible sites, forests could be left entirely to natural regeneration and rarely receive treatment.

Instead of the even-aged, single-species stands commonly established these days, these forests would mainly grow mixtures of broadleaved and coniferous trees, similar to natural stands, and be harvested selectively to always maintain some tree cover.