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Individual Highlight

Aboveground and belowground herbivores control growth and survival of deciduous shrubs in understories of conifer forests

Photo of A radio-collared elk browses on cottonwood in the Starkey Experimental Forest and Range, Oregon. A radio-collared elk browses on cottonwood in the Starkey Experimental Forest and Range, Oregon. Snapshot : These research results on the combined effects of herbivory by cattle, elk, and pocket gophers provide robust new knowledge about how mammalian eating habits affect understory vegetation in dry coniferous forests following fuels reduction and prescribed burning.

Principal Investigators(s) :
Wisdom, Michael, Dr. Naylor, Bridgett
Research Location : Oregon; Starkey Experimental Forest and Range
Research Station : Pacific Northwest Research Station (PNW)
Year : 2017
Highlight ID : 1374


Herbivores can have profound impacts on understory vegetation in the dry forests of western North America, including changing fuel loading and fire risk. The effects can be difficult to assess over short time periods, especially without controlled studies, and most mammalian herbivory effects are assumed to be benign. A team of scientists working at the Starkey Experimental Forest and Range near La Grande, Oregon, conducted an experiment to evaluate the effects of cattle and elk, two large herbivores, on growth and survival of black cottonwood and Scouler's willow. The cottonwood and willow compete with more fire-prone understory plants in post-fire early successional forests and provide important understory habitat for a variety of wildlife. The scientists also monitored belowground herbivory by pocket gophers and explored interactive effects of aboveground and belowground herbivory. They found that pocket gophers reduced survival of both cottonwood and willow while cattle and elk herbivory substantially reduced height growth for both plant species. They documented strong interactions between aboveground and belowground herbivory on shrub survival, demonstrating the synergistic impacts of combined herbivory on these important understory species. This was the first study of the combined effects of aboveground (ungulates) and belowground (pocket gophers) herbivory.

Forest Service Partners

External Partners

  • Oregon State University
  • San Diego Zoo Global Conservation Program