Compounding effects of cattle, wild ungulates, and beaver impede riparian restoration

Planting native woody vegetation is a common restoration practice to increase stream shade, an important salmonid habitat recovery strategy in the interior Pacific Northwest (PNW, USA). Herbivory by domestic livestock and wild mammals, a ubiquitous disturbance in PNW riparian zones, is a common barrier to survival and growth of plantings. Because monitoring is rare, we know little about long‐term effects of coexisting livestock, wild ungulates (elk: Cervus canadensis ; deer: Odocoileus hemionus and Odocoileus virginianus ), and beaver ( Castor canadensis ) on planting performance. We monitored 1688 deciduous‐broadleaf plantings (planted in 2013–2014), over 7 years. Caged ( n = 825, within small fenced exclosures) and uncaged plantings ( n = 863) were tracked across four ungulate treatments: (1) cattle ( Bos taurus ); (2) elk and deer; (3) cattle, elk, and deer; and (4) no ungulates. Cages allowed for paired comparisons to test for effects of protection from ungulates across treatments. We tracked evidence of beaver herbivory, height growth, survival, and flowering for plantings between 2017 and 2019. Cumulative effects of cattle, wild ungulates, and beaver resulted in long‐term arrestment of planting height growth, >90% failure (plantings were either dead or not growing taller) of willow ( Salix spp.) and cottonwood ( Populus balsamifera ), and elimination of willow flowers. Cattle and wild ungulates had similar effects (decreasing growth by ~50%) on growth of willow and cottonwood. However, wild ungulates suppressed growth (~34%) of black hawthorn ( Crataegus douglasii ) and willow flowering (>90%), whereas cattle had no effect on these components. Wild ungulates had broader impacts on plantings compared to cattle; compounding effects of wild ungulates with another herbivore (whether another ungulate or beaver) resulted in long‐term arrestment of planting heights. Our results illustrate that compounding effects of wild ungulate herbivory with livestock and beaver were incompatible with planting objectives in the region. The interactive effects of wild ungulates, livestock, and beaver are rarely accounted for in restoration; our results illustrate that monitoring for these varied herbivory effects is important to evaluate the effectiveness of riparian vegetation restoration and to inform restoration improvements that support recovery of threatened salmonids in stream systems like Meadow Creek in the interior PNW.