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When we think of prescribed fire, we think of burning in the dormant season. However, burning during mid- to late summer is the optimal time to control brush encroachment.

How to use prescribed fire to manage pastures

Often, we think of prescribed fire as viable only during the dormant season. That’s not always the case.

By Russell Stevens

In 1949, Aldo Leopold, an American ecologist and forester, published “A Sand County Almanac. In it, he introduced the phrase “land ethic,” meaning there should be a responsible relationship existing between people and the land they inhabit.

This phrase helped usher in the first major change in human awareness and attitudes toward land management. A chief tenet of Leopold’s land ethic is that “A thing is right when it tends to preserve the integrity, stability and beauty of the biotic community. It is wrong when it tends to do otherwise.”

Prescribed fire, grazing and rest are integral processes for maintaining the integrity, stability and beauty of the biotic community in the Great Plains and throughout the United States. When managing native plant communities, it is impossible to achieve beneficial outcomes when using only the processes of fire, grazing or rest. Fire, grazing and rest are natural processes to which plant communities in the Great Plains have adapted. They should be used in combination with each other.

Of these three natural processes, fire is by far the least-used and least-understood. Landowners say that fear of liability is the No. 1 reason they do not use fire. However, there are several ways to limit liability: Have a burn plan, know your ranch insurance coverage and join a prescribed burn association.

Liability

The best way to mitigate liability is to have a well-thought-out burn plan in writing. A burn plan is a must for anyone using prescribed fire because it identifies goal(s) for the burn, labor and equipment needs, fuel load and fuel type, acceptable wind direction(s), smoke management plan, ignition sequence(s), a map of the burn unit  and more.

In short, a burn plan forces the practitioner to think about, and plan for, all aspects of the burn, and it serves as a communication tool for the burn team and local emergency personnel.

Unfortunately, there are no insurance policies that landowners can buy specifically for prescribed burning. However, many ranch insurance policies cover prescribed burning.

Check with your insurance agent about coverage. Keep in mind that some insurance agents may not be completely familiar with all details in their policy so you may have to do some additional investigation.

Joining a prescribed burn association is another great way to reduce liability as well as learn more about the use and effects of prescribed fire. Prescribed burn associations are local and led by landowners. Members share expertise, labor and equipment in order to assist one another with prescribed fires. Being active in an association is an excellent way to learn about and implement fire in a safe manner.

Applying prescribed fire

Prescribed fire should be applied only when it will help accomplish a goal. Applying prescribed fire under the proper conditions — but in the absence of an adequate fuel load, such as grass — is a wasted effort.

The stocking rate and duration of grazing should be planned to build adequate fuel loads before considering a prescribed burn. When adequate fuel loads consisting of grass are present, careful consideration should be given to make sure the goal accomplished by applying prescribed fire exceeds the need to graze the grass, or that there is enough forage available for both burning and grazing.

This is one reason why light to moderate stocking rates and pasture deferment are important for ensuring there’s enough grass to allow flexibility in management.

Landowners who are appropriately stocked can apply prescribed fire to a portion of their property annually or periodically to accomplish goals. However, for grazing management, it is not recommended to burn more than 25% of the available forage base in a growing season, and the burn should be planned at least a year in advance to ensure an adequate grass fuel load.

If drought alters that plan for the year, the plan can be delayed. Change the dates in the plan, and the plan is still good for the same location in subsequent year(s), when conditions are more favorable.

Fire frequency and return interval

The difference between fire frequency and fire return interval is often misunderstood.

Fire frequency refers to the recurrence of fire in a given area over time and is often stated as the number of fires per unit of time in a designated area.

Fire return interval is the time between fires in a designated area. Where present, tree scars are the most common indicator of fire frequency and return interval in a particular area, assuming the sampled trees were scarred during each fire event.

For example, if tree scars indicate a particular location burned in 10 out of 30 years, then the fire frequency would be once every three years. Counting growth rings between tree scars provide estimates of fire return intervals. If, in our example, the 10 fire events occurred in years 2, 8, 9, 15, 16, 17, 21, 24, 28 and 29, then the fire return intervals would be six, one, six, one, one, four, three, four and one years respectively. 

When to burn

So, how often should landowners burn? Based on prescribed fire research in the southern Great Plains, Oklahoma State University (OSU) developed a rule of thumb that says the application of prescribed fire once every three years maintains brush abundance.

To reduce brush, burn more often than once every three years; brush encroachment usually occurs when land is burned less often than this.

More specifically, depending on precipitation and site productivity, OSU recommends a two- to five-year return interval to manage resprouting shrubs and trees, and a five- to 15-year return interval to reduce fire-sensitive species such as eastern red cedar. For grasslands, time since previous fire is the most important variable to monitor.

Many factors influence whether prescribed fire achieves particular goals. Weather conditions, such as relative humidity and air temperature, and the amount of fuel during the burn are probably the biggest factors.

Rainfall and the presence or absence of grazing affect the amount of fuel and fuel moisture, and the fire return interval. All of these factors affect prescribed fire intensity, which in turn affects the decision regarding the proper fire return interval necessary to achieve the desired goal(s).

The season of burn is another factor to consider that influences the application of prescribed fire. Season of burn can be used to influence forage quality for cattle or to provide better top-kill on woody plants.

For instance, most landowners are familiar with burning native pastures just before spring green-up to remove the previous year’s dead and decaying vegetation, and produce new growth that is lush and of high quality. However, most landowners do not consider burning during mid- to late summer to extend forage quality into the fall and winter months.

Late-summer burning appears to be an optimal time to control brush encroachment as well. It is vital that prescribed fire practitioners monitor annual rainfall to predict forage growth. They also must manage their grazing to ensure adequate fuel loading in order to optimize the outcome of their prescribed burning efforts, regardless of the burn season.

The prescribed fire process warrants serious consideration in rangeland management systems. When used with rest and the grazing management process, it can provide great benefits to cattle and wildlife through forage quality improvement, and more plant diversity and structure.

Being appropriately stocked is the key to managing for proper fuel loads in order to make prescribed burning worth the time and effort.

Stevens is the Noble Research Institute strategic consultation manager and wildlife and range consultant. Contact him at rlstevens@noble.org.

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