Fire models may underestimate fire behavior in tallgrass prairie - observations from southern Ontario

Understanding how fuels and fire behavior are linked is important for those using prescribed fire as a land management tool. The authors of this study sought to:

1) Compare rapid assessment tools for fuel loading,

2) measure fire behavior, and

3) compare observed fire behavior to model predictions (Canadian FBP, Behave, Australian grass)..

To better understand the relationship between fuels and fire behavior in southern Ontario’s tallgrass prairie fuel type, and compare observed fire behavior to model predictions the authors of this study collected detailed fuel and fire behavior measurements. Accurately measuring fire behavior is a challenge, and the intensive sampling for this study is an example of how to collect detailed quantitative fire behavior measurements.

When comparing the model predictions to observed rate of spread, models typically under predicted fire behavior. Even the custom Behave model, which had the highest correlation with observed values, was found to under predict fire spread. The authors found that the model with the most reasonable fit, when considering both correlation and prediction bias, was the Australian grassland fire spread model.

Understanding strength and weaknesses of model assumptions and predictions can help prescribed burn practitioners plan and achieve successful burns.

Management Implications

• A field guide developed from this research is available online: http://cfs.nrcan.gc.ca/publications?id=33093
• Default settings in commonly used fuel models may underestimate fuel loads and fire behavior in tallgrass prairie
• The Robel pole was found to be an accurate rapid assessment of fuel loads in tallgrass prairie sites

For further summary of  the study's results and implications for management, view or download a PDF version of the research brief: "Fire behavior observations from southern Ontario."

The original paper is:

Kidnie, Susan, and B. Mike Wotton. 2015. Characterisation of the fuel and fire environment in southern Ontario’s tallgrass prairie. International Journal of Wildland Fire 24: 1118-1128.

Expansion of woody species in tallgrass prairie

The authors of this study used a combination of long term demographic data and field measurements to investigate what traits allow native woody species to outcompete grasses, even when fire is used as a management tool.

The study was conducted at Konza Prairie Biological Station in the Flint Hills of Kansas.Twenty six years of data from permanent plotsestablished in 1983 were used to examine changes in woody species cover.

In general, the authors found evidence that a positive feedback loop contributed to the ability of Cornus drummondii to encroach tallgrass prairie. Once established, this shrub has a deep root system, spreads via clonal growth, and reduces fine fuels needed to carry fire. These clonal resprouts are more likely to survive fires, and thus able to expand across the landscape at a higher rate. 

Management implications

• Woody cover can increase in tallgrass prairie managed with relatively frequent fire
• Determining the mechanisms that enablewood species to expand is critical formanagement (e.g., species with clonal growth more likely to survive fire or mowing)

For further summary of the study's results and implications for management, view or download a PDF version of the research brief: "Expansion of woody species in tallgrass prairie."

Or read the open access article in the online journal Ecosphere:

Ratajczak, Zak, Jesse B. Nippert, Jeffery C. Hartman, and Troy W. Ocheltree. 2011. Positive feedbacks amplify rates of woody encroachment in mesic tallgrass prairie. Ecosphere 2(11):121.  http://dx.doi.org/10.1890/ES11-00212.1

Fifty years of prairie fire – a case study from Iowa

Small, isolated prairie remnants often show a decline in native species over time, and their sustainability is questioned. Given the rarity of tallgrass prairie in the upper Midwest, it is important to monitor changes over time to determine the long term impacts of land management.

This case study sought to document changes in the vegetation at Kalsow Prairie, one of the largest virgin prairies remaining in Iowa. Management at Kalsow, prior to 1950, was predominantly annual summer mowing, after 1950 management was gradually shifted to spring burning.

Implications for managers:

• Managing the same way over time (e.g., burning in the spring every 2 years) may not maximize biodiversity of the plant community due to the strong selection pressure.
• Larger isolated prairie sites may be less prone to establishment of non-native species when managed with fire
• Prescribed fire may stabilize prairie communities, and keep non-native species from establishing

For further summary of the study's results and implications for management, view or download a PDF version of the research brief: "Fifty years of prairie fire – a case study from Iowa."

The original paper is:

Reference:

Dornbush, Mathew E. 2004 Plant community changes following fifty-years of management at Kalsow Prairie Preserve, Iowa, U.S.A. American Midland Naturalist 151:241-250.

Evaluating sixteen years of restoration in prairie

Long-term studies can track changes over time, and provide examples of expected community trajectory under similar restoration activities. In this study, authors focused on tallgrass prairie remnant at the University of Michigan Nichols Arboretum in Ann Arbor. 

After 16 years of research comparing prescribed fire treatments (annual fires and fires every three years), the authors did not observe changes in dominance or richness related to differences in fire frequency. 

For a summary of the study's results and implications for management, you can view or download a PDF version of "Evaluating sixteen years of restoration in prairie."

This research brief for research managers summarizes the following peer-reviewed publication:

Heslinga, Justin L., Robert E. Grese. 2010. Assessing plant community changes over sixteen years of restoration in a remnant Michigan tallgrass prairie. American Midland Naturalist 164:322-336.

Prairie Burn Management and Native Species Diversity

The varying effects of fire frequency on native prairies continues to be the subject of study and interest among restorationists and ecologists in the Upper Midwest. This study, in prairie remnants in the eastern tallgrass prairie region, took a close look at species composition changes over five decades.

Among several crucial findings, the authors cautioned against site monitoring protocols based on plant species diversity, which in this resurvey remained stable--despite the clear shift toward common species and away from conservative specialist species.

Management Implications

• Continue to burn remnants. A burn regime of 4-17 fires in 20 years had the greatest influence on keeping species composition similar to 1950.
• Put monitoring emphasis on rare species rather than species diversity, as diversity does not always indicate a decrease in rare species.
• Managers may not need to go to great effort to remove all woody species. The most stable prairies had less than 50% canopy cover.

For a summary of the study's results and implications for management, you can view or download a PDF version of "Prairie Burn Management and Native Species Diversity."

This research brief for research managers summarizes the following peer-reviewed publication:

Milbauer, M. L., and M. K. Leach. 2007. Influence of species pool, fire history, and woody canopy on plant species density and composition in tallgrass prairie. J. Torrey Bot. Soc. 134: 53–62. 2007.

Response of tallgrass prairie to fire frequency

This brief summarizes results from a study that was focused on eastern tallgrass prairie sites and examines how fire frequency influences the plant community. To investigate how fire frequency affects eastern tallgrass prairie, sites surveyed in 1976 were revisited in 2001 (25 years later). Sites ranged from those rarely (or never) burned to some which had been burned almost annually.

For a summary of the study's results and implications for management, you can download a PDF version of the research brief here.

The original paper is:

Marlin L. Bowles and Michael D. Jones. 2013. Repeated burning of eastern tallgrass prairie increases richness and diversity, stabilizing successional vegetation. Ecological Applications 23:464-478.