Abstract Willow (Salix spp.) communities are critical components of riparian ecosystems in the Intermountain west, providing key ecological functions such as streambank stabilization, shading, nutrient cycling, and habitat for fish and wildlife. However, browsing by domestic cattle (Bos taurus) and native large ungulates, including elk (Cervus canadensis), moose (Alces alces), and deer (Odocoileus spp.), can strongly influence willow growth, architecture, and recruitment dynamics. Excessive browsing pressure has been linked to reduced canopy cover, impaired regeneration, and altered riparian hydrology, yet few studies have directly compared species-specific browse intensity, preference, and recovery potential of various willow species under shared environmental conditions. To address this knowledge gap, we monitored cattle and large ungulate browsing patterns over four years at two locations in Idaho (Beyeler Ranches, LLC, Lemhi County; UI Rinker Rock Creek Ranch (RRCR), Blaine County). At both locations, cattle grazed only during summer months. Willows were blocked by species, canopy size, and location along streams and randomly selected. Selected willows were tagged in May, measured for height and canopy volume after initial budding prior to cattle grazing. Evaluation of willow browse was measured post-cattle grazing in early-August and again late-September to determine browse utilization over time. Willows were not measured outside the growing season; however, the same willows were measured in the following May to evaluate both winter use and pre-grazing status. Additionally, at RRCR, we compared on-ground field measurements with 3-dimensional point clouds constructed from high-resolution drone imagery to determine whether drones could be used to measure willow canopy volume. Finally, game camera imagery was used to characterize year-round presence or absence of wild ungulates in the areas. Preliminary results indicate that there was utilization of willows by both cattle and large ungulates throughout the growing season. Pre-grazing browse measurements (6%) increased (P 0.05) by 33% during the cattle grazing period when both cattle and wild ungulates were present. An additional (P 0.05) 13% utilization was observed in September, when only wild ungulates were present. Interestingly, while browse of Plane Leaf (Salix planifolia) and Lutea (Salix lutea) willows dropped off after cattle were removed, continued browse of Geyer (Salix geyeriana) willow was observed. These results suggest that certain livestock or wild ungulate species may have different preferences for varying willow species. Techniques used to quantify willow canopy volume highly corresponded (R2 = 0.8) with field-estimated volume, while acquiring and analyzing drone data took 60% less time than field-based measurements. The outcomes of this research provide a more mechanistic understanding of how varying herbivore communities influence willow persistence and associated habitats. Ultimately, these results can help refine adaptive management frameworks and strategic restoration efforts that meet conservation goals while not disrupting other landscape uses, such as livestock grazing.
Ellison et al. (Wed,) studied this question.