MS Thesis Defense | Dan Marshalla

Repeated prescribed fire effects on plant dynamics and communities in central hardwood forests

Fire regimes around the world are changing due to both climate change and fire suppression. This threatens plants and their communities in fire-adapted, oak-dominated forests as fire suppression shifts overstory tree composition, leading to darker and moister conditions on the forest floor and reduced oak regeneration. This has coincided with the invasion of Microstegium vimineum, a non-native grass that enter a positive feedback loop with fire. However, many studies on these issues only analyze single fires or short-term fire effects, while I used two decades of prescribed fire records in southern Illinois’ Shawnee National Forest. I investigated how fire history and Microstegium interact to impact oak seedlings, finding that increased fire benefits oak regeneration partially by disrupting the invasive grass-fire cycle. I also studied the understory plant community, finding that repeated fire alters plant functional traits to be more conservative primarily through intraspecific variation rather than species turnover.