Three Most Powerful Tools for Managing Native Plant Communities

Three of the most commonly used tools for managing native plant communities are fire, grazing and rest. Unfortunately, many land managers do not understand when and how to use these tools; rather, many try to manage native communities primarily with other tools such as mowing, bulldozing, herbicides, tillage or planting. Although, these other tools can be useful and appropriate in certain situations, they should be considered supplemental or secondary tools, but usually are not the primary tools for effectively and economically managing native plant communities.

Plant Succession Management

Fire, grazing and rest work within the process of natural plant succession to change plant communities. Rainfall also has a tremendous impact, but we have no direct control over it. Plant succession is a mostly predictable change of plant species composition in response to disturbances or rest from disturbances. All native plant communities change through the process of natural plant succession. A plant community changes with disturbance or  rest.

Fire is a very useful tool for managing native plant communities.

Native Plant Communities Require Appropriate Disturbances

Fire, grazing and weather extremes are the primary disturbances that historically impacted native plant communities. Depending upon severity, these disturbances retard succession or maintain a successional state, while rest from disturbances during periods of adequate rainfall advances succession. Historically, many upland communities burned frequently either through lightning strike or due to man. Without fire, abundance and dominance of some species such as several native legumes decrease, while abundance and dominance of some species such as juniper increase. Without fire, prairie commonly changes into woodland. Excessive dominance by native forbs such as western ragweed, annual broomweed, bitter sneezeweed or horseweed indicates heavy disturbance, which may be excessive for some goals, and often indicates the need for rest.

The appropriate amount of fire, grazing or rest varies depending upon site, rainfall and management goals. Productive soils and areas with relatively high rainfall typically require or tolerate relatively frequent fire or grazing to satisfy many goals. For example, prairie maintenance in much of the eastern US probably requires a fire every 1-2 years. Whereas, less productive soils and areas with relatively low rainfall typically require or tolerate less frequent fire or grazing, and typically require more rest to satisfy many goals. For example, the most productive/desirable plants in a desert usually tolerate only infrequent fire or grazing and generally require long periods of rest.

Other Tools May Be Appropriate in Certain Situations

Even though fire, grazing and rest are the disturbances that native plant communities developed under, sometimes other tools can be appropriate. It may be necessary and appropriate to use a bulldozer, chain saw or tractor-mounted shear to remove woody cover when fire has been excluded from an area for too many years. Spot treatment with an herbicide might be appropriate when addressing a non-native invasive plant because such plants are not part of the native ecology and control may require extraordinary measures. Planting and or fertilization may be appropriate when native seed bank and soil characteristics have been altered through decades of cultivation or herbicide treatments.

Sources of Help

Range conservationists, wildlife biologists, and foresters can help land managers better understand and manage native plant communities. Such assistance is often available from state organizations such as state extension services, state wildlife or conservation agencies, and state forestry services, federal agencies such as the Natural Resources Conservation Service, and US Fish and Wildlife Service, and private organizations such as The Samuel Roberts Noble Foundation and The Nature Conservancy.

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. 

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.

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.

 

Influence of Fire on Grazing Distribution

Bison selecting post-fire regrowth (foreground) over dormant, unburned vegetation (background). Photograph by Stephen Winter.

Fire is a primary driver of many ecosystems, but is particularly important in the establishment and maintenance of grasslands and savannas. Numerous research studies have shown the effects and importance of fire on several grassland ecosystem properties, including plant productivity, plant species composition, nutrient cycling, and woody plant encroachment. Many North American grasslands support large grazing animals, either native wildlife (e.g., bison, elk) or introduced livestock. The role of grazing is also critical to the development and maintenance of grasslands, influencing many of the same processes as fire.

Though often considered independent, fire and grazing interact and influence one another. This is referred to as the fire-grazing interaction or pyric-herbivory (defined as grazing driven by fire). This interaction occurs when fires are present within a landscape or pasture allowing grazing animals to choose between burned and unburned areas. Due to high forage quality of post-fire regrowth, many animals are attracted to recently burned areas, including bison, cattle, elk, deer, sheep, and many others. Because of the differences in forage quality, grazing distribution is altered as animals heavily graze recently burned areas and avoid areas with greater time since fire. The preference for burned areas is very strong, and will often be greater than selection or avoidance of other features (e.g., water, topography, etc).

As fires move around the landscape or pasture, animals will follow to consume nutritious regrowth. This interaction between fire and grazing creates a mosaic or gradient of recently burned and grazed areas to areas with greater time since fire and no grazing. Across a landscape, the differences among such areas increase the number of plant and animal species (diversity), affects invasive species establishment, and nutrient cycling rates also vary with time since fire. Using the interaction of fire and grazing as a management tool can help conserve or restore ecosystem processes while maintaining livestock production.

 

Patchy fire within the bison unit at the Tallgrass Prairie Preserve in northcentral Oklahoma; there are no fixed burn units. The response of grazing animals to the patchy distribution creates the fire-grazing interaction.

 

 

What is Patch Burning?

What is Patch Burning?

Patch burning (patch-burn grazing) involves the combined use of fire and grazing for ecological or agricultural goals within landscapes or pastures.  The target area or pasture is subdivided using only needed burn lines (no cross fencing).  Each year fire is used to burn a different portion of the pasture.  Livestock can be added to the area at anytime.  The grazers will be attracted to the burned area and spend most of their grazing time in that portion of the pasture.  As fire moves around the pasture or landscape, grazing pressure will also change in synchrony.  The focal area or patch will incurr heavy grazing creating a grazing lawn type structure.  As grazing pressure is released, the plant community recovers and a shift mosaic is created. 

Patch burning allows livestock to freely select the most recently burned part of a pasture. It has been found that livestock spend 75% of their time on these burned patches and, typically, evenly utilize all the palatable plants within the entire burned patch. This includes plants that are normally not considered desirable livestock forage. Then within 6-12 months another portion of the pasture can be burned. This will shift the focal grazing point to the new burn patch. After the heavy utilization (1 to 4 years post-burn depending on the chosen rotation) a transition state of bare ground, forbs, and small amounts of standing biomass and litter occurs. Within a couple of years post-burn, the patch receives very little grazing pressure which allows biomass and litter to accumulate (Figure 3). This rested patch is then ready to be burned and grazed again. This is all accomplished without fences. The total amount of hands on management is much less with this system than many other common grazing systems.  For more information about patch burning go to the following link http://pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-4677/E-998survey.pdf 

 
Patch burning (patch-burn grazing) is the purposeful grazing of a section of an landscape or management unit that has been prescribed burned, and then rotating fire through the managment unit to move the grazing pressure over time. This creates a shifting mosaic on the landscape or management unit.

 

 

Cattle spend 75% of the time grazing on the most recently burned patches. This allows the other patches to recover.

 

How does fire impact grazing?

Recently burned areas attract grazing animals because of increased forage quality and palatability. Recently burned areas also have fewer external parasites such as flies and ticks which influence habitat use. Grazing animals follow fires; thus, fire can be used to rotate animals across the landscape. However, animals tend to concentrate on these areas until a more recent burned area is available; thus, when a manager wishes to move livestock, fire is a good tool to achieve this.

Should I defer grazing after a fire?

The decision to rest or graze a pasture following fire is not necessarily a trivial question. There are numerous variables and potential interactions to consider (e.g., condition of resources following fire, and potential weather in the months ahead). Generally speaking, plant communities that are adapted to fire are also adapted to grazing following a fire. However, timing, intensity, distribution, and duration of grazing as well as the type of livestock must be considered and adjusted accordingly to meet management objectives. If reseeding is necessary following fire, some deferment may be appropriate until the new plants are established. In some cases, deferment may be necessary to allow woody plants to become established and grow beyond the reach of herbivores.

For information regarding prescribed burning and grazing in the Great Plains see Patch Burning: Integrating Fire and Grazing to Promote Heterogeneity. For information regarding grazing following wildfire in the Great Plains see Management after Wildfire.

Are fire and grazing interrelated?

Yes, grazing animals preferentially forage on recently burned areas due to the increased palatability of new and re-sprouting vegetation. As a result, fine fuel loads at these sites are reduced, subsequently lowering their near-term burn potential. Conversely and simultaneously, fine fuels on adjacent unburned areas buildup in the absence of concentrated grazing resulting in an increased burn potential over time. The result is an ever-changing mosaic of burned and unburned patches across the landscape driven by the interaction between fire and grazing.