Is a prescribed fire sufficient to slow the spread of woody plants in an infrequently burned grassland? A case study in tallgrass prairie

Authors: NIPPERT, JESSE - Kansas State University; TELLERIA, LIZETH - Kansas State University; BLACKMORE, PAMELA - Kansas State University; TAYLOR, JEFFREY - Kansas State University; O'Connor, Rory

Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2021
Publication Date: 7/1/2021
Citation: Nippert, J.B., Telleria, L., Blackmore, P., Taylor, J.H., O'Connor, R.C. 2021. Is a prescribed fire sufficient to slow the spread of woody plants in an infrequently burned grassland? A case study in tallgrass prairie. Rangeland Ecology and Management. 78:79-89. https://doi.org/10.1016/j.rama.2021.05.007.
DOI: https://doi.org/10.1016/j.rama.2021.05.007

Interpretive Summary: Woody plant expansion into grasslands is changing the nutrient and water cycles of the ecosystem, as well as its diversity and is decreasing available forage for livestock. We used a spring prescribed fire in a woody encroached grassland to observe if a single prescribed fire can cause mortality in the woody plants present and see if there is also a lagged mortality effect on those woody plants two years post-fire. We found that the woody species that are either clonal and/or resprout had low to none mortality from the prescribed fire, however, a fire sensitive species Eastern Red Cedar (Juniperus virginiana) saw almost 80% mortality after two years post-fire; the individuals that survived were buffered by other woody plants that did not suffer fire mortality. Understanding that single-use spring prescribed fires are not enough to eliminate all of the woody plants in a woody encroached grassland, but that additional restoration measures are needed to eliminate the woody plants.

Technical Abstract: In many mesic grasslands, such as the central Great Plains in North America, frequent fire is a key regulator of ecological processes. Long periods of infrequent fire facilitate the conversion of herbaceous-dominated grassland to woody-dominated shrubland or woodland. At the Konza Prairie Biological Station in northeast Kansas, one infrequently burned portion of the landscape has undergone transformation from grassland to woodland after nearly 30 yr without fire. In Spring 2017, a prescribed burn was implemented to assess fire effectiveness on woody plant mortality. A postfire census of 3 000+ individual woody plants identified the distribution of species by size (height), topographic position, and slope on the landscape. Mortality and canopy fire damage were calculated for each individual. In lowland locations with near-continuous shrub cover (30.7% of the landscape), woody plants were unaffected by fire. However, in upland and slope locations, where shrubs and trees were sparser, survival probability varied by topographic position and species. In these locations 68% of all woody individuals experienced 90% or greater fire damage to the canopy, with 56% of these individuals exhibiting new canopy regrowth within 2 mo after the fire. The two most abundant woody shrubs, Cornus drummondii and Rhus aromatica, showed high survival at all height classes and landscape positions. The two abundant tree species, Gleditsia triacanthos and Juniperus virginiana, showed increased survival probability with tree height that varied by landscape position. Survival of J. virginiana also varied according to proximity and size of neighboring clonal shrubs, providing a mechanism for persistence of this fire-sensitive tree species even at small height classes. The probability survival curves developed here are useful for managers assessing when to prescribe fire to maximize mortality for J. virginiana and provide insight relevant for broader ecological understanding of woody encroachment within grasslands throughout the world.