Harvesting

In Alberta, areas designated for harvest are usually cut in two stages, or "passes." In the first pass, one half of the merchantable timber is logged using a patchwork pattern designed to fit into the landscape. The pattern alternates between harvested patches ("cutblocks"), and unharvested patches ("leave blocks") of similar size. The leave blocks are harvested in the second stage, 10 to 20 years later when the cutblocks harvested in the first pass are growing well again as new forests.

The seedlings of some tree species (for example, lodgepole pine and aspen) have adapted to open conditions. They regenerate and grow well in the soil and sunlight conditions of cleared areas (similar to the conditions created by forest fires). For this reason, the two-pass system tends to be the most economical and appropriate technique for harvesting these types of forests. Harvesting must be done properly, in accordance with provincial legislation and policy, in order to protect sensitive watersheds and the ecosystems of rivers.

The size of cutblocks varies, but maximum average sizes are given as guidelines by the Alberta government. For spruce trees, maximum cutblock size may vary from 24 hectares to 32 hectares depending on the type of block. For pine and deciduous trees, cut blocks may average 60 hectares and individual blocks may be as large as 100 hectares. Average cutblock size in Alberta over the last three decades has varied from 10.9 to 24.2 hectares for coniferous species, and from 13.2 to 46.0 hectares for deciduous species.

Department of the Environment. State of the Environment Report, Terrestrial Ecosystems. Edmonton: n.p., 2001. With permission from Alberta Environment.