Floral response of eight forb species to prescribed fire in the southern Great Plains (U.S.A.)

Prescribed fire is commonly used to restore and maintain grasslands, often mediating the balance between grasses, woody species, and forbs. Forbs provide the majority of plant diversity in grasslands, and the responses of forbs to fire are important to understanding and predicting the effects of fire on pollinators and on plant communities. However, much of the past research on prescribed fire effects in grasslands has focused on woody plant species and grasses, not forbs, despite the importance of their flowering dynamics to pollinators. Thus, we need to know more about the mechanisms underlying the responses of forbs to fire, especially in the understudied southern Great Plains. In this study, we asked whether the floral displays of eight native forb species in this region differed between burned and unburned plots, and, if so, whether the differences were due to plant density (plants/m2), plant size (grams dry above-ground biomass), resource allocation to flowers (flowers/gram plant biomass), or a combination of these factors. We found that fire responses were highly species-specific. Prescribed fire increased floral display (flowers/m2) of five of the eight species. Floral display was proportional to plant size and plant density (plants/m2). In some species both size and density were larger in their burned plot; while other species show opposite or no patterns. The species-specific responses of forbs in this study reinforces the need to better understand and manage for increased forb diversity and overall heterogeneity to recreate or restore ecosystems that can support a wider variety of organisms and conserve biodiversity.