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1 January 2015 Forest-Floor Disturbance Reduces Chipmunk (Tamias spp.) Abundance Two Years after Variable-Retention Harvest of Pacific Northwestern Forests
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Abstract

We evaluated the two-year effects of variable-retention harvest on chipmunk (Tamias spp.) abundance (fi01_75.gif) and habitat in mature coniferous forests in western Oregon and Washington because wildlife responses to density/pattern of retained trees remain largely unknown. In a randomized complete-block design, six treatments were applied to 13-ha units at three sites (blocks): four retention levels of original basal area (BA) in an aggregated tree pattern (100, 75, 40, and 15%) and two retention levels in a dispersed tree pattern (15 and 40%). Log-yarding method differed at each site (suspension cable, shovel-loader, or helicopter). We used an information-theoretic approach to compare six candidate regression models for their ability to predict treatment responses of chipmunk fi01_75.gif and associated habitat variables. Chipmunk fi01_75.gif had a positive linear relationship with retention level that predicted a 50% reduction in abundance as % BA retention decreased from 100 to 15% (R2 = 0.36). Disturbed soil cover was strongly related to the interaction of retention level and block (i.e., yarding method and other site-level differences) (R2 = 0.82), and the model predicted disproportionately greater disturbed area for cable yarding (16%) than for shovel (10%) or helicopter (6%) methods as retention decreased from 100 to 15%. Chipmunk fi01_75.gif had a negative linear relationship with disturbed soil cover that predicted a 70% reduction in the species' abundance as disturbed area increased from 0 to 16% (R2 = 0.53). Retention level and yarding method are important considerations when planning harvesting operations because of their potential impacts to small mammal populations.

Randall J. Wilk, Timothy B. Harrington, Robert A. Gitzen, and Chris C. Maguire "Forest-Floor Disturbance Reduces Chipmunk (Tamias spp.) Abundance Two Years after Variable-Retention Harvest of Pacific Northwestern Forests," Northwest Science 89(1), 75-92, (1 January 2015). https://doi.org/10.3955/046.089.0106
Received: 10 January 2014; Accepted: 1 October 2014; Published: 1 January 2015
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