The response of Keen's mice populations to riparian restoration treatments on Lyell Island, Haida Gwaii

Abstract

The complexity of the forest floor in the pacific coastal forest is largely dependent on coarse woody debris and light transmitting though the forest canopy for promoting understory plant growth and diversity. The purpose of my study was to test the importance of coarse woody debris (CWD) and canopy light transmission to habitat quality for Keen's mouse (Peromyscus keeni keeni) in young riparian forest stands (60-70 years) one year following the creation of small canopy gap openings (.03ha). Abundance, demography (age and sex), and body condition (weight) of the Keen's mouse were studied by mark-recapture live-trapping over a 2-year period - one year pre- and one year post-treatment. Two watersheds - Powrivco and Sandy Creeks - were selected for this study on Lyell Island in Gwaii Haanas National Park Reserve. At the scale of the home range (~1 ha) Keen's mice showed no short-term response to small canopy gap treatments which did produce increases in CWD volume and piece length, significantly so at sites in Sandy Creek (p=<0.05). Canopy light transmission did not change after treatment, even in Sandy Creek where restoration treatments significantly reduced stem density (p=0.001). Keen's mice were more abundant and larger in the second growth riparian forest of the Powrivco watershed than Sandy Creek, likely due to higher structural complexity and a large deciduous canopy component.