Pinegrass Response to Understory Disturbance in a Recently-harvested Dry-belt Douglas-fir Forest

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• promotion of a higher proportion of open forest, and open range area
• provision of additional forage production, emphasizing native bunchgrass recovery
• provision of additional habitat for grassland and open forest dependent wildlife species

Plant community targets of a restoration plan often emphasize increasing the abundance of bunchgrasses such as bluebunch wheatgrass (Pseudoroegneria spicata) and fescue species (Festuca sp.) and reducing the abundance of pinegrass (Calamagrostis rubescens). However, when pinegrass is present in the pre-treatment plant community, it has proven to be very persistent, often increasing in response to overstory removal.

The objective of this study was to examine the response of pinegrass to different levels of forest floor disturbance in recently thinned forest stands. Understanding how pinegrass responds to disturbance may provide insight on how to reduce pinegrass colonization following restoration treatments.

Forest floor plots containing pinegrass at a Douglas-fir (IDFxh2) site were disturbed to different levels to determine pinegrass response.

Plots were treated by hand to achieve:

• control (no treatment)
• partial removal of forest floor organic material (LFH) (leaving one-half of the average LFH depth of the site)
• complete removal of forest floor organic material to mineral soil
• complete removal of forest floor organic material and removal of the top 5 cm of mineral soil