The Impact of Fuel Load, Burn Season, and Fire Frequency on the Control of an Invasive Legume, Sericea Lespedeza

The Impact of Fuel Load, Burn Season, and Fire Frequency on the Control of an Invasive Legume, Sericea Lespedeza

Summary

Our project has made a significant amount of progress since the initiation of the project.  We have completed two years (2015 and 2016) of post annual-fire data collection on sericea lespedeza density, abundance, growth, and reproduction measurements.  The first year of data suggests that fall fire alone will not reduce sericea lespedeza density or productivity, but when used in combination with mowing it is nearly as effective at reducing productivity as herbicides.  More critically though, fall fire nearly eliminates the seed production for that year.  Fall fire also changes the reproductive output and allocation so that plants put significantly fewer resources into reproduction.  We have also collected ground-level data for spring fires in 2016 to begin building a fire temperature model.  We were unable to obtain infrared data using the drones in spring 2016 because of camera difficulties, but we hope we have corrected the problems.  We acquired a different infrared camera that we hope will provide us with better, usable data for the 2017 spring fire season.

Objectives/Performance Targets

Objective 1:  Evaluate total standing biomass, grass standing biomass, and sericea lespedeza standing biomass in response to burn season coupled with herbicide, mowing, and fuel load addition treatments.

Objective 2:  Evaluate sericea lespedeza growth and reproductive output in response to burn season coupled with herbicide, mowing, and fuel load addition treatments.

Objective 3: Build a fire model based on fire conditions and common management practices to predict burn conditions necessary to produce fire temperatures lethal to sericea lespedeza seed.

Objective 4:  Determine the economic cost of managing sericea lespedeza infestations with fire and other supplemental treatments compared to herbicide application alone.

Accomplishments/Milestones

Objective 1:  Evaluate total standing biomass, grass standing biomass, and sericea lespedeza standing biomass in response to burn season coupled with herbicide, mowing, and fuel load addition treatments.      

Data from the first year (2015) of post-fire treatments have been analyzed, and have shown that shifting prescribed fire from spring to fall has no negative affect on grass or total standing biomass.  Shifting fire to fall alone did not reduce sericea lespedeza standing biomass or stem density, but coupling fall fire with mowing significantly reduced sericea lespedeza standing biomass so that it was not statistically different from the herbicide treatments.  The only treatment that eliminated sericea lespedeza completely was an herbicide application of triclopyr.  These early data suggest that grazing, mowing, and/or hay production combined with switching prescribed burning from spring to fall may be a successful strategy to manage this invasive plant species.  Samples from the 2016 growing season have been collected and are still being processed.  Analysis of these samples will likely be completed by May 2017.

Objective 2:  Evaluate sericea lespedeza growth and reproductive output in response to burn season coupled with herbicide, mowing, and fuel load addition treatments.

We also found that fall fire coupled with mowing had the greatest influence on plant growth and reproductive capacity.  Seeds on the plant experience over 90% mortality when the plant is burned in fall, which likely reduces the annual contribution of seeds into the seedbank.  In addition, plants that were burned the previous fall produce nearly half as many seeds per plant than plants that experience spring fire.  Plants experiencing fall fire before the beginning of the dormant season will also have significantly less investment into seed production than plants exposed to fire during the previous spring as shown by the seed mass: aboveground biomass.  The seed mass:aboveground biomass was approximately 0.01-0.60 g/g for fall burned plants while it was approximately 0.4-2.5 g/g for spring burned plants

Objective 3: Build a fire model based on fire conditions and common management practices to predict burn conditions necessary to produce fire temperatures lethal to sericea lespedeza seed.

                We have run into some difficulties with this portion of the project.  The infrared camera was not operating correctly during our prescribed burns in spring 2016, but we have purchased a different camera that we anticipate will work for our burns in spring 2017.  We still have the ground data for the prescribed burns from spring 2016.  That data shows that temperatures are higher under patch-burn grazing management than under annual-burn grazing management, and that head fire heights are significantly taller under patch-burn grazing than under annual-burn grazing management.  There is also a significant correlation between litter load, litter moisture and fire temperature.  We hope to be able to determine time duration that fire temperatures exceed critical temperatures that are lethal to sericea lespedeza seeds.

Objective 4:  Determine the economic cost of managing sericea lespedeza infestations with fire and other supplemental treatments compared to herbicide application alone.

                This objective will not be addressed until year 3 of this study.

Impacts and Contributions/Outcomes

Conference Presentations

Lingenfelter^†, E, BA Koerner.  April 2016.  Three Minute Thesis: The impact of fuel load and fire season on the control of sericea lespedeza.  32^nd Annual Research and Creativity Forum, Emporia State University, Emporia, KS.  (1^st place recipient of the Three Minute Thesis Competition)

Lingenfelter^†, E, BA Koerner.  April 2016.  The impact of fuel load and fire season on the control of sericea lespedeza.  32^nd Annual Research and Creativity Forum, Emporia State University, Emporia, KS.  (poster presentation)

Piva^†, M., and BA Koerner.  April 2016.  Fire season and litter load effects on the control of sericea lespedeza.  32^nd Annual Research and Creativity Forum, Emporia State University, Emporia, KS.  (Oral presentation)

Piva^†, M, E Lingenfelter^†, and BA Koerner.  February 2016. Control of sericea lespedeza: Impacy of fuel load, fire season, and fire frequency on plant density.  Kansas Natural Resources Conference, Wichita, KS.  (oral presentation)

Lingenfelter^†, E, M Piva^†, BA Koerner.  February 2016.  Management implications on the growth and reproductive capacity of an invasive legume, sericea lespedeza.  Kansas Natural Resources Conference, Wichita, KS.  (poster presentation)

Koerner, BA, M Piva^†, and E Lingenfelter^†.  September 2015.  Control of sericea lespedeza: Impact of fuel load and burn season on plant density.  America’s Grasslands Conference.  Fort Collins, CO. (poster)

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