Eastern redcedar trees — the most rapidly expanding woody species on the Great Plains — are one of the biggest threats to the ecology of the Nebraska Sandhills.
“Simple transitions in vegetation systems can have far-reaching impacts,” said Dirac Twidwell, rangeland ecologist in the University of Nebraska–Lincoln Department of Agronomy and Horticulture. “Trees taking over rangelands can affect working lands in complex ways, even impacting our well-being in metropolitan areas.”
When eastern redcedars dominate a landscape, the impacts can be severe:
- 75 percent decline in forage for livestock
- Nearly all plants and wildlife unique to grasslands may become rare or locally extinct
- $400,000 annual cost for Nebraska public schools to control redcedars on grazing leases
- Increased potential for cedar apple rust, a fungus that can grow on cedar trees and harm fruit trees
- Increased wildfire danger potential that may make standard suppression tactics ineffective.
The spread of redcedars is not limited to Nebraska. It also is problematic in Texas, Oklahoma and Kansas, and experiences in those states have proven that prevention is a better option than control, Twidwell said.
Prevention of redcedar encroachment is a complex social-ecological issue, he said. From the time Nebraska became a state, planting trees in grasslands was not only accepted but also encouraged, without the knowledge that planting redcedars in the Sandhills would eventually contribute to the loss of resilience of natural resources. As a result, redcedar, a juniper species native to Nebraska, was planted in many windbreaks throughout the state because the trees are sturdy, long-lived and drought-resistant.
One of the easiest ways to stop the spread of redcedars is to stop planting them and remove the source of spreading — seeds. Cutting off small redcedar seedlings by hand can remove newly established individuals, but it is labor intensive and requires careful monitoring. Additionally, seedling establishment increases over time and can compete with time spent on other necessary ranch management operations.
If prevention is not implemented, large redcedars can be removed using mechanized equipment, but the practice is cost-prohibitive and results in only small acreages being managed, Twidwell said. In Nebraska, the cost to mechanically remove redcedars from 1,000 acres is estimated to be $150,000 to $250,000. Costs have increased in Southern Plains states, where redcedar is more common, to approximately $1 million for 1,000 acres.
Prescribed fire is an effective tool for controlling the spread of seedlings; however, as the trees grow larger the fire intensity must increase in order to kill them. The live fuel moisture must be low enough in the large trees to allow the fire to scorch the crowns to be effective.
Increased awareness of the redcedar encroachment across the state may help decrease some of the current ineffective management, Twidwell said. “Prevention is critical to conserve the Sandhills, one of the largest remaining grasslands in North America.”
When an ecological base is shifting, resilience can be compromised, he said. “It's not just about these trees, it's about changes to the ecosystem. It's a matter of when the ecosystem is going to be affected, not if, and how those changes influence Nebraskans’ ways of life.”
More information is at cedarliteracy.unl.edu/ and agronomy.unl.edu/twidwellresearchteam.