Prairie fire as a selective agent: Second-generation responses and plant community shifts

Background/Question/Methods

Prescribed fire has been used extensively as a prairie restoration tool, but its specific impacts on prairie plant communities are not always interpreted within a spatially or evolutionarily explicit framework. For example, plant community responses to fire can be related to both treatment scale and the selective impact of fire on plant phenotypes, but neither factor is accounted for in most plant community studies. Here, we used experimental paired prescribed fire and fire-exclusion plots to examine the effects of realistic large-scale prescribed fire on prairie communities in western Washington State. As a case study of fire’s potential selection effects, we collected seeds from a common prairie plant (Lomatium utriculatum) to examine second-generation effects of burning (in the previous year) on seed vigor. Lomatium utriculatum seeds were germinated and grown in cooperation with the Sustainability in Prisons Project, where inmates had active roles in the care, tracking, and measurement of the plants, providing a valuable opportunity for science education and inmate contributions to ecological restoration. Lomatium utriculatum is an essential nectar source for the federally endangered Taylor’s checkerspot butterfly (Euphydryas editha taylori), and it may serve as a surrogate for the effects of fire on endangered species recovery. 

Results/Conclusions

Prescribed fire both altered plant communities and increased germination of L. utriculatum. Plant species diversity (Shannon’s and Simpson’s indices) and richness were increased in burned treatments, and unburned plots showed higher soil C:N ratios, which may have driven some of the observed community shifts. Lomatium utriculatum seeds collected from burned plots had increased germination following the exposure of parent plants to fire, exhibiting a second-generation effect of burning the parent plant. Overall, this study demonstrates that prescribed fire could play an important role in altering prairie composition and may be a potential selective force driving plant micro-evolution in ecologically important species.