Benscoter, Brian

Shortened periods of inundation due to water management have led to the encroachment and expansion of Carolina willow (Salix caroliniana) in sawgrass (Cladium jamaicense) marsh communities. Morphologic and physiologic differences between sawgrass and willow have potential consequences for microhabitat conditions and ecosystem function such as a reduction in temperatures and light availability and changes in primary productivity. Since it is a woody shrub, willow is often assumed to exhibit higher rates of transpiration than non woody plants, which in turn can affect photosynthesis and carbon exchange and ultimately wetland water management. In this study willow was found to have higher rates of stomatal conductance (gs) and photosynthesis (Anet) than sawgrass. However, sawgrass had greater intrinsic water use efficiency (WUE) than willow. This suggests that willow is capable of greater gas exchange and carbon assimilation than sawgrass but requires more water. Understanding the implications of willow expansion will improve landscape models of wetland water and carbon exchange and inform water management decisions.

Changes in vegetation may influence the quality and quantity of the underlying
organic peat soils and have impacts on faunal populations. My goal was to determine
whether shifts from native slough communities to invasive cattail in the Florida
Everglades could affect peat characteristics that could cascade to impact the dry season
survival of crayfish (Procambarus fallax). I contrasted peat soils from native slough and
cattail-invaded sites as alternative dry-season burrowing substrates for crayfish. Cattail
peat had higher average bulk density and inorganic content within the first ten
centimeters of the soil profile. Crayfish showed marginally greater initial burrowing
success in slough peat than in cattail peat but survival was equivalent in both peat soils
and high overall. Understanding these indirect linkages between vegetation and crayfish
populations in the Everglades can provide insight on the consequences of plant invasion
on ecosystem trophic dynamics.