Conifer Underplanting & Release

Rock Creek underplanting

We planted a number of different species of conifers in the Rock Creek riparian area.

Where conifer-dominated riparian forests have been replaced by deciduous trees following timber harvest, the recruitment of large, decay-resistant conifer LWD (large woody debris) into the stream is much lower. In order to increase future recruitment of functional LWD into streams in these areas, SPU is increasing the size and density of conifers in these stands in two ways.

First, where there are no or very few conifers, conifer seedlings (such as western red cedar, Sitka spruce, and western hemlock) are being planted in areas cleared of understory and overstory competition. This is generally done in circular patches or in areas already cleared during road decommissioning or invasive plant removal.

In mixed conifer-deciduous stands, conifer release is a treatment that aims to increase the growth rate of existing conifers. Understory shrubs and overstory alder trees that are suppressing naturally recruited conifers are cut back to release the conifers from competition with these plants. Faster growing conifers should reach a size that will provide functional LWD sooner than they would without release.

Riparian forests targeted for conifer underplanting and release are generally along low gradient stream reaches, where deciduous trees are more common and where fish species of concern are present. Because of the high effort involved in clearing and maintaining planting areas, conifer underplanting where understory competition is high is being done on a relatively small scale.