Prescribed fire is a historic land management tool dating back to the American Indians, who used it to promote green grass for buffalo. The practice controls encroachment of woody plants such as juniper and mesquite and improves soil health by creating plant diversity. A third benefit is the removal of dead plant growth which can fuel wildfires. Prescribed fire is very effective in managing seedling trees and shrubs. The smaller or more immature encroaching brush, the more successful the prescribed fire will be in suppressing or killing invasive trees and shrubs. Fire is effective at suppressing resprouting brush such as: redberry juniper and mesquite. However, prescribed fire will kill non re-sprouting brush like: Ashe juniper, Eastern red cedar, pricklypear, etc..
Figure 1. A small, immature redberry juniper seedling was suppressed due to a summer, growing-season prescribed fire. However, the larger trees in the background were left unaffected by the prescribed fire.
Figure 2. Eastern Redcedar seedling before (right) and following (left) prescribed fire.
Invasive Resprouting Trees and Shrubs Commonly Found Throughout the Great Plains
Invasive Non-resprouting Trees and Shrubs Commonly Found Throughout the Great Plains
Prescribed fire can control non-resprouting trees like Ashe juniper or Eastern redcedar that are 6-ft. tall or smaller under average burning conditions. The following are prescribed fire conditions that will be effective in managing non-sprouting trees and shrubs that are within the target height:
Source: Eastern Redcedar Control and Management – Best Management Practices to Restore Oklahoma’s Ecosystems (factsheet NREM 2876)
Figure 3. Relationships between shrub height class (m) and probability of mortality following extreme fire treatments in the Edwards Plateau of West-Central Texas.
Larger trees and shrubs that are older, more mature, and typically taller than 6-ft can be managed with prescribed fire, but usually more than the initial fire treatment is required or intense fire effects. Higher levels of mortality of adult resprouting plants have been observed for some species when exposed to high-intensity fires (Brad-stock & Myerscough 1988; Adie et al. 2011). Anthropogenic constraints on fire behavior may be masking the theoretical potential of fire as an agent of vegetation change (Twidwell et al. 2016a). Extreme fire is a technical term that has been used commonly in the US wildland fire community since the 1950s (Potter & Werth 2011) to describe atypical behavior in high intensity fires that lead to blow-ups, fire storms, fire whirls and other forms of erratic fire behavior. A single extreme fire in drought in the Edwards Plateau of Texas resulted in shrub densities that were 35 –55% lower than shrub densities in control treatments (not burned). Densities of resprouters were lower 3-years after applying extreme fire because mortality of established individuals exceeded recruitment of new individuals for multiple brush species, whereas recruitment exceeded mortality in non-burned plots, despite drought conditions. A single extreme fire in drought resulted in shrub densities that were 35 –55% lower than shrub densities in control treatments (not burned, no herbicide) also subject to drought conditions, and the magnitudes of change were remarkably consistent at both sites (Fig. 2). Densities of resprouters were lower 3 years after applying extreme fire because mortality of established individuals exceeded recruitment of new individuals for multiple species, whereas recruitment exceeded mortality in control plots, despite drought conditions.
The following are prescribed fire conditions that constitute extreme:
Figure 4. A mature Redberry juniper tree burns during a summer prescribed burn in the Edwards Plateau in West Central Texas.
Another option to achieve intense fire effects is to accumulate more fuel prior to burning. Consistent and heavy fine fuel loads will ensure appropriate amounts of consumption. Accumulated fuel loads will also increase the potential for fire to climb into ladder fuels that are adjacent to tree canopies. Achieving consumption and scorch height goals and objectives can be done in two ways. One option is to defer grazing before burning in order to accumulate increased fine fuel. The more arid the environment, the longer the deferment period in order to achieve appropriate fine fuel loads. Another option is to change livestock grazing patterns to accumulate more fuels in certain areas of the pasture. Patch burning can be an effective tool to achieve a heterogeneous landscape that optimizes plant species diversity.
Prescribed fire in the spring helps plants start growth earlier and summer and fall prescribed fire helps plants continue growth later in the fall. This extends the season of palatable, high quality forage and reduces the amount of winter protein supplementation livestock producers need to feed.
Prescribed fire is an effective method to change animal grazing patterns in a pasture. Areas far from water and areas with moderate slopes are normally avoided by most cattle. When these areas are burned cattle can spend up to 70% of their time on the recently burned patches.