Forage Composition, Productivity, and Utilization in the Eastern Washington Cascade Range

Provision of forage for wild and domestic ungulates, and the associated impacts of their herbivory, are contentious issues for wildland management in western North America. We quantified the composition, above-ground net production (ANP), and utilization of herbaceous and shrub vegetation in five non-forest and seven forest cover types across the core spring-summer-fall range of the Yakima elk herd in the eastern Washington Cascade Range. We randomly sampled each cover type along three elevational transects during a two-year period. Riparian/meadow was the most productive cover type (2,752 kg ha(-1) ANP). High-productivity forest at low to high elevations produced 900-1200 kg ha(-1) ANP. High-elevation forest and grassland, shrubland, and shrub-steppe produced 600-700 kg ha(-1) ANP. The low-productivity forest cover types and parkland produced 100-400 kg ha(-1) ANP. Utilization of forbs, grasses, and shrubs combined averaged 47% of ANP across all cover types, ranging from 26% in high-elevation forest to 63% in shrub-steppe. Grasses and forbs were equally utilized at about 57% of ANP, whereas shrubs were utilized at only 4% of ANP. Twenty-two of 55 shrub species accounted for the majority of shrub productivity and showed little to no long-term browsing; but, several shrub species were moderately to severely hedged. Moderate to high levels of ungulate utilization indicate potentially strong impacts of ungulate herbivory on pattern and process in eastern Cascades forests. Dry forest restoration management to reduce fuel loads and restore resiliency to disturbance likely will increase forage for ungulates, especially in closed-canopy true fir and Douglas-fir stands.