Defend the Core, Grow the Core: Tackling Eastern Redcedar Encroachment in Nebraska’s Grasslands

Defend the Core, Grow the Core: Tackling Eastern Redcedar Encroachment in Nebraska’s Grasslands

What’s the problem?
Nebraska’s grasslands are declining as woody plants like eastern redcedar spread and take over what were once intact and treeless grasslands1. This process, referred to as woody plant encroachment, is among the greatest threats to Great Plains grasslands. Every year, more of our grasslands are lost due to woody encroachment (Fig 1). In 2019, Nebraska lost more than 419,000 tons of forage production to woody encroachment2. Past management approaches have largely been unable to stop or reverse this trend3 (but see example of collaborative management from Nebraska’s Loess Canyons region4).

Woody encroachment stages in Nebraska from 1990 to 2021 and descriptions of the stages of encroachment and associated management actions
Figure 1. (Top) Woody encroachment stages in Nebraska from 1990 to 2021. (Bottom) Descriptions of the stages of encroachment and associated management actions.

What’s the Solution? A new concept for management, known as “Defend the Core, Grow the Core”, is becoming widely adopted among producers and natural resource groups for confronting woody encroachment on the state’s grasslands (Fig 2). Instead of focusing on heavy infestations where making gains is most difficult, the idea is to anchor management to intact grassland areas and target surrounding low and moderate infestations to gain back ground and grow a grassland core.

Illustration of the “Defend the Core, Grow the Core” concept used to better manage regional threats like woody encroachment.
Figure 2. Illustration of the “Defend the Core, Grow the Core” concept used to better manage regional threats like woody encroachment. Instead of emergency care, this approach focuses on proactive management where there are greater chances for long-term success.

What’s wrong with the past approach (emergency care)? And why is the new approach (proactive, preventative care) better? Management treatments within heavily encroached areas can cost hundreds to thousands of dollars per acre5 and require intensive short- and long-term follow-up management. In the short term, follow-up management is needed to kill the thousands of seedlings per acre that sprout after the initial treatment6. Without this follow up, managers will quickly have a bigger problem than when they started. In the long term, constant management is needed to keep pace with seedling recruitment as seeds pour in from surrounding seed sources (a mature eastern redcedar tree can produce over 1.5 million seeds per year7, the majority of which are dispersed within 200 yards of the tree8). Meanwhile, the front lines of the problem are advancing into previously intact grasslands where the most cost-effective opportunities for management were missed. By anchoring management to intact grasslands and targeting the leading edge of the problem (e.g., seeds, seedlings, and scattered seed sources), managers can impact more acres and have a better chance of long-term success (Fig 3).

As a steward of Nebraska’s grasslands, how can I get started building a core?
When you are out planning practices for your land, consider where you have intact grasslands, where the leading edge of encroachment occurs, and where you can treat the most acres with the least effort. Instead of treating 100 acres of dense infestation, can you treat 1,000 acres of low infestation on the leading edge?

Even better, talk to your neighbors about growing a grassland core across properties. We give encroaching woody plants an advantage when we limit our planning to the boundaries of a single property. Efforts to solve the encroachment problem are more successful when neighbors collaborate and work together, including collaborations that span private and public land.

 

The leading edge of encroachment into an intact grassland.
Figure 3. The leading edge of encroachment into an intact grassland.

How big does a core need to be?
There is no single correct size for building a grassland core. Instead, the goal is to maximize the size of the core based on the context of a landscape or region. In more intact grassland regions, there’s potential to establish large core areas relatively quickly, while in more infested regions, smaller cores can help protect remaining grassland values. What’s more important is that we get started defending grassland cores, and the sooner the better.

Click here for the full management guide on how to defend and grow grassland cores.

Sources

  1. Twidwell, D. and others. (2021) Reducing woody encroachment in grasslands: a guide for understanding risk and vulnerability. Oklahoma Cooperative Extension Service, E-1054.
  2. Morford, S. L. and others. (2022). Herbaceous production lost to tree encroachment in United States rangelands. Journal of Applied Ecology, 59(12), 2971-2982.
  3. Fogarty, D. T. and others. (2020). Woody plant encroachment and the sustainability of priority conservation areas. Sustainability, 12(20), 8321.
  4. University of Nebraska. (2021) Loess Canyons Experimental Landscape: Science Report. University of Nebraska-Lincoln, Large-Scale Rangeland Conservation Lab. Lincoln, Nebraska.
  5. Simonsen, V. L. and others. (2015). Act now or pay later: the cost of reactive versus proactive eastern redcedar management. University of Nebraska Extension, EC1784.
  6. Fogarty, D. T. and others. (2021). Rapid re-encroachment by Juniperus virginiana after a single restoration treatment. Rangeland Ecology & Management, 78, 112-116.
  7. Holthuijzen, A. M. and Sharik, T. L. (1985). The avian seed dispersal system of eastern red cedar (Juniperus virginiana). Canadian Journal of Botany, 63(9), 1508-1515.
  8. Fogarty, D. T. and others. (2022). Spatial patterns of woody plant encroachment in a temperate grassland. Landscape Ecology, 37(11), 2835-2846.

 

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