Category: Controlled Burn

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Influence of Fire on Cattle Forage Quality

Cattle grazing on a burn

Importance of Fire

Fire is an important driver of many North American ecosystems, particularly grasslands.  The influence of fire on the plant community is largely attributed to its removal of dead standing plant material, impact on forage quality, and the impact on grazing animals.  Cattle production in undisturbed tallgrass prairie can be low due to the accumulation of dead standing plant material.  However, fire can increase production over 75%.  Historically, large bison herds followed fire as they were attracted to the lush regrowth that emerged.  Today, managers use prescribed burning to capitalize on this change in forage quality for cattle production. 

Forage Quality

Forage quality is typically expressed as crude protein (CP) which is based on the nitrogen content of forage. This nitrogen content is critical for microorganisms in the rumen.  Other measures of forage quality include palatability (typically associated with texture and moisture content) and digestibility (largely based on fiber and lignin). The primary influence of fire on forage quality is the removal of standing, dormant plant material.  Forage quality is largely a function of time: as plants age (mature) they decrease in quality.  This decrease in quality is due to the increase in fiber and lignin content, resulting in reduced digestibility and animal consumption.  Prescribed fire remove dormant plant material, increasing the nutrition and digestibility of post-fire regrowth. While prescribed fires are commonly conducted during the late winter or early spring, growing season (summer) fires have the same effect and can boost forage quality during a period of the year where it is typically decreasing.  Furthermore, the interaction of fire and grazing will impact below ground plant growth by increasing nitrogen mineralization and plant nitrogen availability, and improving the root tissue quality.

Benefits of Higher Forage Quality

Forage quality is a critical component of cattle production including reproductive efficiency, rebreeding, calf production, animal growth and milk production.  Understanding the importance of fire to native rangeland plants and the potential benefits to cattle can be a useful tool for ranch managers. 

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Michael D. Porter

Michael D. Porter is a senior wildlife and fisheries consultant with the Samuel Roberts Noble Foundation in Ardmore, Oklahoma. He has worked with the Foundation for 33 years. Through the Foundation, Mike provides wildlife and fisheries management technical assistance to land managers in south-central Oklahoma and north-central Texas. Prior to working with the Noble Foundation, he was self-employed as an independent wildlife management consultant to ranchers in South Texas. His career has been devoted to helping people, especially land managers, better understand and conserve wildlife and fisheries resources.

Mike earned a Bachelor of Science Degree in wildlife and fisheries sciences and a Master of Agriculture Degree in wildlife science from Texas A&M University. Mike is a certified wildlife biologist, a certified professional in range management, a certified Oklahoma hunter education instructor and a certified Oklahoma aquatic resources education instructor.

Mike has considerable experience managing white-tailed deer, northern bobwhite, eastern bluebird, beaver, waterfowl, largemouth bass, channel catfish, bluegill, grass carp, ponds, hunting leases, prescribed fire, woody plantings, aquatic vegetation, soil erosion as well as other natural resource issues.

 

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The Great Plains Fire Learning Network, Reconnecting People, Lands and Fire

The Fire Learning Network (FLN), is a cooperative program of the US Forest Service, Bureau of Indian Affairs, Bureau of Land Management, US Fish and Wildlife Service, and National Park Service, along with The Nature Conservancy. This network supports public-private partnerships in landscapes that are engaged in collaborative fire planning and implementation, providing a means for sharing and vetting tools and innovations to help expand the use of fire for natural community restoration.  FLN communities have been established nationwide and an e-newsletter is regularly publshed.

Three Focal Landscapes of the Great Plains Regional FLN

Among the 47 FLN landscapes now working to accelerate restoration at local, regional and national scales are the three focal landscapes of the Great Plains regional FLN: the Loess Hills (Iowa), Lower Loup River (Nebraska) and Refugio-Goliad Prairie (Texas). These landscapes provide leadership, share lessons learned, and maintain a link to the national FLN for other Great Plains landscapes, including the Prairie Coteau (South Dakota), Niobrara-Sandhills (Nebraska), and Southern Iowa.

Working Hard to Make a Difference in the Landscape

The FLN is working hard to advance lessons learned from mangers and private landowners and to apply them at a scale that will make a difference in the landscape. Strategies include supporting landowner burn associations, helping volunteer fire departments offer prescribed fire to their community members, creating mobile burn crews and offering prescribed fire training exchanges (TREX). As a result of these efforts, 56,000 acres have been treated with prescribed fire during TREX events since 2008.  TREX events are a great way to learn from experienced fire professionals as well as to share your skills with others.  Look for the annual calls for participants.

To learn more about the FLN and these fire training exchanges visit: http://www.conservationgateway.org/topic/fire-learning-network.

Pre-burn briefings set the stage for successful burns.  Maps, whether computer generated or hand drawn, can improve communication.  Folks from state, federal, county, The Nature Conservancy, and a volunteer fire department  discussed plans for the day’s burn.  Photo by Susanne Hickey.

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What weather conditions are important to consider when planning and conducting a prescribed fire?

The primary weather conditions to consider when planning and conducting a prescribed fire are relative humidity, wind speed and direction, temperature, and mixing height. Most prescribed fires are conducted with relative humidity between 30–50%. Burning with relative humidity below 25% can be tricky as spotfires are likely and suppression becomes challenging. Burning with relative humidity above 50% is often ineffective because of high fine fuel moisture content. Forecast wind speed is for winds 20 feet above surrounding obstructions. The actual wind speed at ground level is usually less. Wind speeds of 2-15 miles per hour are common for most prescriptions. Winds greater than 15 miles per hour can create containment challenges in the event of an escape or spotfire. Mixing height is the distance aboveground where smoke is mixed with the atmosphere. The mixing height and transport wind speeds at that elevation influence smoke dispersal. A mixing height of at least 1,700 feet is recommended for most prescriptions.

 

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Livestock Weight Gain and Patch-burn Management

Achieving optimum livestock production on rangelands many times can conflict with wildlife conservation strategies that require lower stocking rates to maintain suitable habitat. Traditionally, livestock producers try to maximize gain per-acre by uniformly managing vegetation in pastures. Often this is achieved either by heavily grazing, burning the entire pasture, or both. This management strategy can create suitable habitat for some wildlife species, but poor quality habitat for others. 

Patch Burning

Combining the spatial and temporal interaction of fire and grazing (patch-burning) a conservation-based approach to land management can be achieved. This practice can increase rangeland biodiversity by creating heterogeneous vegetation structure and composition that is beneficial to multiple wildlife species. However, for conservation strategies to be successfully implemented, they need to be both effective and economically sustainable. In both mixed-grass prairie and tallgrass prairie, cattle weight gain was compared in pastures with traditional fire and grazing management (continuous grazing, with periodic fire on tallgrass prairie and seasonal grazing without fire on mixed-grass prairie) and conservation based management (pyric-herbivory applied through patch burning), both at a moderate stocking rate. Stocker cattle weight gain, calf weight gain, and cow body condition score were comparable between the traditional and conservation based management at the tallgrass prairie site for the duration of the eight-year study, indicating that conservation management doesn’t decrease livestock production or profitability.

In the mixed-grass prairie pastures, stocker cattle gain was not different between traditional and conservation management for the first four years. However, stocker cattle in conservation based management out gained cattle in traditional management beginning in year five and remained 27% greater for the next six years of the study. Moreover, cattle weight gain under conservation management varied less year to year making profitability more consistent. Traditional management in mixed-grass prairie did not include fire, the process that improved range conditions and likely was associated with increased stocker cattle performance under conservation management. In conclusion, pyric-herbivory is a conservation-based rangeland management strategy that returns fire to the landscape without reduced stocking rate, deferment, or rest.         

Figure 1. Cattle weight gain on traditionally managed and patch-burn managed tallgrass prairie.

 

Figure 2. Cattle weight gain on traditionally managed and patch-burn managed mixed-grass prairie. An * indicates years when patch-burned managed cattle gained more than traditionally managed cattle.

 

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Burning in the Growing Season Effects on Grass

When land managers start a prescribed burning program they often wonder whether fire will kill their grass, particularly during the growing season. To answer this question, the history of grasslands/shrublands needs to be considered. Fire is common through much of North America as a natural disturbance and a land management tool. Native Americans used fire as a part of their everyday existence from cooking meals to preparing camp sites and even hunting and warfare. With so much fire being used, historically, landscapes burned throughout the year. However, the intentional use of growing-season fire as a management tool remains controversial due to potential damage to fire sensitive herbaceous plant species that may be of benefit to both livestock and wildlife. 

Growing-season grazing is a common practice that, if done at appropriate stocking rates, can benefit pastures as a whole. The common practice of growing-season grazing and growing-season fire were compared to see if there was a difference in plant growth and survival. For 10 years, plant communities burned in the dormant season and during the growing season and were monitored. The study found that the particular time of year that the fire occurred did not affect the plant community. The amount of rainfall was the dominant driving factor affecting grass production.

Figure 1. The relative abundance of little bluestem in pastures burned in the dormant season or the growing season. The solid line represents the rainfall received on the pastures the previous growing season.

Individual little bluestem plants were burned at multiple developmental stages to see how growing-season fire affected survival and growth. Plant age was the primary factor affecting plant survival with nearly all seedlings dying when burned. However, once plants reached 18 weeks old, survival was nearly 100%. Plant survival was similar for plants that were burned or clipped to simulate grazing suggesting that growing-season burning doesn’t have any greater effect on plants that grazing. One advantage that growing-season burning had was that both aboveground production and belowground biomass were both increased after burning, while growing-season clipping reduced production. 

Figure 2. Above-ground grass production on plants either burned and clipped or clipped alone.The letters represent groups that had similar production.

Figure 3. Below-ground  root production on plants either burned and clipped or clipped alone.The letters represent groups that had similar production.

Grasses in the Great Plains are well adapted to both grazing and burning during the growing season and can be included in a successful land management strategy.

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Burning During A Drought

Drought

Landowners often are unable to carry out their fire program due to periodic droughts.  Drought does present several challenges to using prescribed fire such as: lack of fuels, dangerous conditions, and burn bans. However, even during droughts, conditions safe to burn are often present. Further, droughts present some opportunities to meet certain objectives such as reduction of overstory fuels and creating a patchy burn. 

Concerns

One of the primary limiting factors of a drought relative to fire is the lack of fine fuels.  Lack of precipitation can lead to a reduction in grass growth in grasslands and leaf production in hardwood forests.  These fine fuels are needed to carry fires.  Therefore, fires many be patchy in nature or not carry across the burn unit at all. Another issue is that droughts are often accompanied by high temperatures and wind speeds which make conducting prescribed fire unsafe.  Even when conditions may be safe, burn bans may remain in place for long periods of time during droughts due to perceived risk by policy makers.  Droughts can place stress on plants and animals, and therefore many landowners are concerned about carrying out a fire that may negatively impact these already stressed plants and animals. The lack of rain following a fire is also a concern as grass and other plants may not respond and allow for extended periods of lack of cover, forage, and erosion potential.

Opportunities

The concerns listed above can also be viewed as opportunities.  For instance, patchy burns are sometimes the desired outcome.  This is especially true for wildlife management.  If only 50% of the burn unit is consumed by fire, this may be exactly what the prescription called for. If the manager is attempting to remove overstory forest cover, burning during dry conditions when trees are stressed may be the perfect time to accomplish the objective (assuming you can safely carry out the fire). 

Considerations

Always ensure that the fire is carried out under safe conditions that you have a reasonable chance of containing the fire.  While burning during extreme conditions may yield desirable outcomes, safety is the first priority.  Ensure there is adequate personnel and equipment for the conditions and that the burns are legal at all times. 

As weather is always an unknown, it is advisable to hedge and only burn portions of the landscape during droughts.  This will ensure that some cover, forage, etc will remain until favorable weather returns.

Soil erosion is often a concern after a fire during drought as there is little ground cover.  Much of this concern is unfounded as root biomass has tremendous soil stability potential.  However, on steep slopes and in certain soil textures, extra considerations may be warranted.

A final consideration is that fire frequency is the most important consideration regarding fire effects.  Thus, you should do everything possible to maintain the appropriate fire frequency to meet your objectives. This will often mean burning under conditions that are not perfect.  At times when fire is not possible, remember that you will need to burn those units as soon as conditions allow to stay as close to the appropriate fire return interval as feasible.

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Using Prescribed Fire to Control Invasive Plant Species

Eastern Redcedar

Prescribed burning is a vital part of successful land management in grassland and shrubland landscapes. Restoring fire often results in increased vegetation productivity and diversity of species (both plants and wildlife). There is great interest in using prescribed burning to restore pastures that are overrun by invasive plant species, particularly with the rising cost of herbicides. Several factors are important when considering whether prescribed fire will be useful in controlling invasive species.

Plant type

Successful control of invasive plant species often is determined by the type of plant that is targeted. Generally there are two broad categories used to characterize plants 1) resprouters and 2) non-resprouters. Resprouting plants are those that are capable of growing again from roots when the top is removed. Non-resprouting plants are incapable of growing again after the top is removed and die. Prescribed burning can be a very successful strategy when trying to control non-resprouting plants as it often will kill the plant. Resprouting plants can be much more difficult to control and fire is often used in tandem to other control methods such as grazing, herbicides and mechanical control.

Fire Return Interval

The fire return interval is how often a particular piece of land is burned. For example, if a pasture is burned every three years, then the fire return interval would be three years. Native plants evolved in regions with specific fire return intervals. For grasslands, research suggests that fire return intervals for tallgrass prairie were 3-5 years, 4-7 years for mix-grass prairie and 7-15 years for less productive short grass prairie. In western landscapes, return intervals can be much longer with sagebrush ecosystems burning every 50-100 years. Burning within these suggested return intervals will promote the plants native to that region. Burning more or less frequently may harm native plants and allow exotic and invasive plants to become more abundant.

Season of burn

Many regions have seasons when fire is more common than others. In landscapes where snow covers the vegetation during winter months, fire is limited to summer and fall months. Other regions where winters are mostly snow free, fire is common throughout the year. Plants that evolved with fire seem to be less affected by season of burn than those that evolved without fire. Burning plants when they are actively growing is a good strategy to suppress growth and reproduction of invasive plants. Over several burn cycles, this can greatly reduce the abundance of the target plant in pastures. Also, burning when plants are growing can be safer because fires are often slower and less intense.     

Prescribed burning can be used to control invasive species, but a one-size fits all approach will not work and invasive species control must be included in a successful fire prescription.

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Can prescribed fire be used to manage sericea lespedeza?

Fire is one management tool that can be used to control the dominance of sericea lespedeza (Lespedeza cuneata). Data from Kansas and Oklahoma suggests growing-season fire can be more detrimental to sericea than dormant-season fire. Prescribed fire can limit sericea seed production if burned before the plant produces seed. Following fire, sericea is palatable to livestock as tannin levels are lower immediately following germination or resrouting as compared to a mature plant. Using a patch-burning system (e.g., burning a portion of a pasture each year) higher levels of sericea consumption by livestock have been demonstrated as cattle concentrate or continuously graze on the recently burned patch. Using patch-burning, coverage of sericea has increased at a lower rate as compared to more traditional fire and grazing applications where the entire pasture is burned. In some cases, a combination of burning, grazing and herbicide applications may be necessary to control sericea.

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Can I use herbicide, grazing, or mechanical methods rather than prescribed fire?

This depends on your management goals and objectives. Consider the fact that fire has unique properties and different effects that cannot be completely duplicated with other methods. For example, the heat from fire is necessary for seed germination in some plant species, the chemical-physical reaction from fire can alter nutrient availability and affect forage palatability, and increased soil temperature following fire can alter plant emergence in spring. The opposite also holds true.  That is, herbicide, grazing, and mechanical methods can produce results that fire cannot exactly duplicate. Therefore, it is important to understand and define your management objectives in order to best apply the appropriate practice(s). Visit with your local Extension agent or specialist to help make this determination.

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