Canada: British Columbia: Restoration in Coastal British Columbia Riparian Forests

International Forest Products Ltd. and Western Forest Products Ltd.

Early results show speeding restoration through silviculture can yield significant benefits. Through planting, sites devoid of conifers can be restocked, but later brush removal is needed to ensure survival. Overstorey trees that shade out desirable understorey trees can be removed, allowing existing or planted trees to thrive. Wood not needed for stand structure can be added to streams or allowed to lie on the ground to provide nourishment for soil or habitat for wildlife.

Establishing a treatment regime that best suits the wildlife needs of a site can be difficult, however. The removal of too few trees may not allow retained trees to achieve their maximum diameter growth response. Removal of too many trees may yield larger diameter trees, but too few for future use by wildlife, snag recruitment or in-stream debris. Significant effort was expended in adding wildlife habitat features to stands, but little actual use was observed. Some features fell victim to the very wet ecosystems in which they were placed; dens and cavities filled with water, making boxes cut for mice and voles more valuable for salamanders instead.

An unexpected result of the treatments was the very positive impact of girdling. Girdling was incorporated into stand treatments to remove overstorey alder for releasing understorey conifers. It was also used to leave standing structure in conifer stands in order to mitigate tree damage by wind-throw. Girdling exceeded all objectives. In conifer stands, the leafless trees provided large standing structure that gradually opened the site to light, and wind-throw was not observed in stands where girdled trees had been left in place. Girdling produced large standing structure at a fraction of the cost of manually topping trees. Although girdled trees may topple quickly, standing snags in areas where trees were formerly girdled suggest that many will decay and break, leaving natural snags similar to those manually cut by topping but at a fraction of the cost.

1998-07-20

2002-07-20

Historically, timber harvesting has been carried out in many riparian areas. From a logging standpoint, these areas typically have large timber and are among the most accessible terrain. Many accessible riparian areas around coastal streams have been logged at some point following World War II (or earlier via selection hand logging). More stringent guidelines began to be implemented in the 1980s and onwards. Clear-cut harvesting in coastal riparian areas often results in conversion to deciduous stands on the wetter sites (typically alder, Alnus rubra, but also cottonwood, Populus balsamifera ssp trichocarpa, and bigleaf maple Acer macrophylum). These generally develop a variable and often sparse conifer understorey of western red cedar, Sitka spruce and western hemlock. The drier sites typically form dense stands of conifers, often with western hemlock as a leading species. The successional trajectory of these stands following clear-cut harvesting does not necessarily generate the lower density, structurally diverse stands that often existed pre-harvest, at least not in a timeframe that humans would consider reasonable.

UNSURE

UNSURE

YES

The 12 projects focused on thinning overstocked conifer stands, releasing conifers suppressed by overstorey alder, and replanting with preferred (for the site) coniferous riparian tree species. The achievement of old-forest conditions by creating stands of larger, well-spaced conifer trees was the primary objective of the projects. These treated stands will help maximize current and future habitat value; enhance structural and compositional diversity; and ensure a future source of large woody debris for the adjacent streams.

More follow-up monitoring will be required to understand the long-term effects on the forest and any further treatments required.