Undergraduate Research

Evie Von Boeckman

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Shifting Composition in Upland Oak Forests: Potential Impacts on Forest Flammability Due to Changing Fuel Moisture and Drying Rates.

Senior wildlife, fisheries and aquaculture major Evie Von Boeckman studied how an increase in fire-sensitive, shade-tolerant species (mesophytes) impacts moisture content and drying rates in fuel beds, and if fuel bed wetting method (soaking, rainfall simulation, natural rainfall event) influences these response variables. Mesophytes are becoming dominant in historically fire-maintained and oak-dominated (Quercus spp.) forests in the eastern U.S. This could have large impacts on forest flammability, and thus maintenance of oak forests, if mesophyte leaf litter traits influence fuel moisture. This study hypothesized that as mesophyte contribution increases, moisture would be retained longer causing slower drying rates. We also anticipated that the natural rain event method would most closely represent the conditions leaf litter would normally experience, so differences among fuel bed types would be most distinct. To test these hypotheses, we constructed fuel beds in the lab comprised of upland oak litter (Q. stellata, Q. coccinea) and increasing amounts of mesophyte (Liquidambar styraciflua, Carya spp, Ulmus alata) litter (0%, 33%, 66%, and 100%). We wetted fuel beds by, (1) soaking for 24 hr, (2) simulating a summer precipitation event (0.0072 cm over 10 min), and (3) exposing litter to a natural winter rain event (0.19 cm over 4 hr). All treatments exhibited a rapid initial (within 4 hr) decrease of moisture followed by a more gradual decline over the 48 hr drying period; however, beds comprised only of mesophyte litter dried slowest, while those with high oak contribution (66% and 100%) dried fastest. The simulated rainfall and rain event produced similar drying rates; soaking, however, showed the highest moisture content initially and less distinction and separation between drying rates. These findings suggest that increased contribution of mesophyte leaf litter to fuel beds will increase moisture and slow drying rates, which could hinder forest flammability in upland oak systems.