Open Access Kent State (OAKS)

During the past 50 years, Eastern red cedar (Juniperus virginiana), native to the Eastern United States, has been encroaching into grassland/prairie ecosystems in the US. Eastern red cedar (ERC) outcompetes native species, forming dense monocultures and lowering biodiversity. The process of encroachment occurs through seed dispersal by birds and mammals. The outer covering of seeds provides nutrients when other food is scarce, and foraging increases due to the lack of other resources in winter. In avian species, seed dispersal depends on distance traveled based on whether birds are resident, nomadic, or migratory. Mammals and resident birds typically disperse seeds short distances while nomadic or migratory birds tend to move seeds longer distances. We focus on seed dispersal of the ERC using wildlife cameras to monitor bird and mammal foraging behavior in two grassland habitats. Cameras were placed at the crown and base of five trees at each site to observe foraging. We focus on the seasonality of foraging behavior by birds and mammals and how it influences seed dispersal and encroachment of ERC. Mammal species observed include white-tailed deer, Virginia opossum, Eastern cottontail rabbit, and rodents. Birds using ERC include robins, cedar waxwings, bluebirds, and blue jays. Mammalian foraging was very consistent over time, while birds were more episodic in their use of ERC. Overall, mammals and resident bird species were most consistently observed and likely to be important for short-distance seed dispersal, while nomadic and migratory birds have a greater potential for longer-distance dispersal of Eastern red cedar.

Bioturbation is a process by which certain animals, including, burrowing invertebrates alter sediment nutrient (only N is considered here) dynamics as well as bacterial community composition. In this study, two burrowing bioturbators (Hexagenia bilineata and Lumbriculus variegatus) with distinct modes of burrows formation were used. Sieved wetland sediment from Observatory Wetlands at Kent State University campus was used since pilot studies revealed it to be conducive for burrowing by the bioturbators of choice. The experiment was for 7 days and microcosms (transparent PVC pipes of 20 cm height and 5 cm inner diameter) were set up in triplicates for respective bioturbators and control treatments. Microcosms were filled with sediment (10cm) and topped with site water (5cm). Surface and interstitial water samples were taken every alternate day for nitrate and ammonium analysis. Sediment cores of all the microcosms were sliced at different depths at the end of the experiment and subsamples were used for potential denitrification rate (using acetylene inhibition technique) assessment, bacterial enumeration and DNA extraction (to examine bacterial community composition). Surface water nitrate data shows that H. bilineata facilitates nitrate uptake while L.variegatus releases nitrate in respect to controls, and nitrate concentrations varied significantly over dates (P<0.01) and burrower species (P<0.001). Sediment potential denitrification rate was highest for H. bilineata followed by L.variegatus and control. Presence of bioturbators increased denitrification rates and bacterial counts at greater depths. Ongoing work is focusing on assessing bacterial community composition. In conclusion, we can state that bioturbation impacts nutrient fluxes and bacterial communities.

The effect of projected 21st Century climate change on hydrological variables in Old Woman Creek estuary was evaluated using 20 Coupled Model Intercomparison Project Phase 5 (CMIP5) precipitation and temperature projections as input to the Soil and Water Assessment Tool (SWAT). Model calibration and validation was done using the Multi-Objective Evolutionary Algorithm and Pareto Optimization. PRISM climate data for the period 1985 -2014 compared with the average of the 20 CMIP5 models show good agreement in both precipitation and temperature with CMIP5 exhibiting low variability across models. Flow, sediment, and organic nitrogen analyzed from simulations run with PRISM show good correlation with the average of 20 CMIP5 simulations. The performance of each of the 20 CMIP5 inputs to the SWAT model was tested using Euclidean distance relative to their average. The three best CMIP5 models (GFDL-ESM2M, MPI-ESM-MR, EC-EARTH) were used for seasonal analysis. The analysis was done in one past and three future climate windows (1985 -2014, 2018 -2045, 2046 -2075 and 2076 -2100). For the historical period, the result shows an over-estimation of flow, sediment and organic nitrogen from January to March in the SWAT model runs with CMIP5 inputs, relative to runs with the PRISM input. Peak flow, sediment and organic nitrogen were observed changing from winter to spring across the time periods. The expected seasonal and annual changes in each variable over the 21st century have implications for algae growth and general health of the Old Woman Creek estuary.