Current Research
My dissertation research focuses on the factors that influence native plant establishment and discourage invasive plant establishment on stream restoration projects, as well as the differences in plant communities between restored reaches of stream and unrestored reaches. Research will focus on different scales, from broad landscape factors (e.g., proximity to urban areas, land use) to within reach factors (e.g., soils, vegetation structure), to determine which factors promote native plant establishment. Comparisons between restored and unrestored reaches will examine differences in species composition, structure, and invasion and evaluate whether restoration actions have improved streamside vegetation. In addition, bioacoustic monitoring will be used to determine potential differences in the soundscape between restored and unrestored streams as well as along a gradient of non-native plant invasion. Sampling for this project began in Summer 2023.
Past ResearchVegetation and nutritional changed over 20 years of white-tailed deer (Odocoileus virginianus) exclusion
I examined the effects of overabundant white-tailed deer on vegetation. There is a lack of studies in the southeast on the effects of deer browsing on vegetation, as well as a lack of long-term herbivore exclusion studies. Because deer are selective browsers, they have the capacity to change both the composition (by selecting against preferred species) and structure of forest understories. Most natural predators of deer have been extirpated and we are reliant on hunters to control deer populations. Hunter recruitment is decreasing while the amount of usable space, in the form of agriculture and managed forests, for deer is increasing creating a need to understand the effects of overabundant deer. In continuation of an exclusion study which began in 2000, I collected data 20 years after the exclosures were built. I utilized three paired exclosure and control plots on each of three Wildlife Management Areas in Mississippi (Choctaw WMA, Sunflower WMA, and Leaf River WMA), for a total of 9 paired plots. Data on vegetation composition, vegetation structure, canopy closure, and overstory and midstory basal area were collected. In addition to studying the changes in vegetation structure, composition, and regeneration, I also be examined possible differences in the nutritional carrying capacity between exclosure and control plots. Between year effects were most influential for species composition and structure metrics. The lack of herbivory effects possibly could be attributed to regional differences in forest structure, other disturbances, and observed deer densities. Additionally, there was a lack of difference in nutritional carrying capacity due to herbivory, though regional differences highlight the potential for additional management actions to improve available forage. For more in-depth information, see Ripa et al. 2023. Determining the effect of Chinese privet (Ligustrum sinense) invasion on the occurrence of ground-dwelling herpetofauna species
In bottomland forests of the southeastern United States, Chinese privet (Ligustrum sinense) is a common and highly invasive shrub species that can substantially change native communities. Prior research has focused on potential impacts on bees and earthworms, however virtually no studies have evaluated if it changes the habitat for ground-dwelling species such as amphibians (e.g., salamanders, toads, tree frogs) and small reptiles (litter-dwelling snakes and lizards). To address this knowledge gap, a study was initiated in 2019 on a large property (>7000 ac) with extensive bottomland forests on the Black Warrior River in Moundville, AL. Using this property, 60 long-term forest monitoring plots (circular plots, 10-m radius) were established across the property: 20 dominated by mature Chinese privet, 20 with little to no privet present, and 20 actively undergoing restoration by fire. Over 9 months in 2019-2020, data were repeatedly collected on key habitat variables related to ground-dwelling species including: leaf litter, soil moisture, and temperature. These data will be compared to corresponding herpetofaunal data surveyed at the same plots. Herpetofaunal surveys consisted of timed-area searches (conducted seasonally over one-quarter of the plot) and cover-board data (collected monthly). By gathering microhabitat and herpetofaunal data, associations between important habitat variables and ground-dwelling species will be determined. These results will provide an assessment of the relative risk that Chinese privet invasion poses to these fauna and insight into the potential implications for herpetofauna of fire as a restoration tool. |