Higher densities of S. invicta in the United States relative to South America are explained mainly by the absence of natural enemies and low interspecific competition (IC). Despite advances in S. invicta management, broadcast insecticide baits remain as the primary tool for effective control. I studied interspecific interactions of ants and the use of baits on the management of S. invicta to test the following hypotheses: 1) relative abundance of native ants increases ~25% for bait treated sites compared to untreated, 2) behavioral dominance by S. invicta decreases ~10% in bait treated sites compared to untreated, and, 3) foraging by S. invicta on insecticide baits is higher ~10% in low native ant densities areas compared to high densities. Experiments were conducted on three sites with different densities of native ants (low, medium, high), but with similar densities of S. invicta. An enhanced BACI (Before/After-Control/Impact) design was used. Experimental units consisted of 0.4 ha plots. Three treatments were randomly assigned to units and replicated four times; 1) Slow acting bait, 2) Fast acting bait, 3) Untreated Control. Samples and observations were collected for several weeks before/after the treatments to account for temporal variation and to determine rates of reinvasion. Ants were monitored using pitfalls and food lures. Interspecific competition was determined by applying placebo bait. Results indicate that different management methods did not impact resident ants when they are at low and medium densities and that S. invicta is greatly affected; at high native ant density, competition for these baits is observed affecting both natives and S. invicta. Reinvasion of S. invicta was reduced in areas of low and medium native ant densities previously treated with baits and native ant abundance increased by ~25%. At high native ant densities, reinvasion of S. invicta was similar to Control sites. I conclude: 1) properly used, baits can help in recovery of native ant species that then compete with S. invicta; however, rote re-treatments may have a negative impact on restored populations. 2) “bait failures” may be due to interspecific competition when initial native ant densities are high. Preliminary management considerations and recommendations are presented.

Projected climate change may alter soil carbon dioxide (CO2) efflux from terrestrial ecosystems; yet disentangling effect of plant species from climate drivers remains a key challenge. We explored the effects of the dominant plant species, warming, and precipitation distribution on soil CO2 efflux, its underlying components, and mycorrhizal abundance in southern post oak savannah. Post oak savannah in the south-central US are dominated by three contrasting plant functional types: Schizachyrium scoparium (Michx.) Nash. (little bluestem) a C4 grass, Quercus stellata Wangenh.(post oak)a C3 deciduous tree, and Juniperus virginiana L. (eastern redcedar) a C3 evergreen tree. Monocultures and tree-grass plots were warmed using infrared heaters and precipitation events were manipulated to intensify summer drought and augment cool season precipitation. Soil CO2 efflux, the root, bacterial and hyphal components of CO2 efflux, and mycorrhizal abundance were measured. Soil CO2 efflux varied with seasonal changes in soil VWC and temperature, with higher soil CO2 efflux rates in the spring and lower rates in both the cooler winter season and at the end of the dry summer period. There was no relationship between root length density or root mass density and soil CO2 efflux during the short term precipitation distribution campaigns. Partitioning of root, fungal, and bacterial component contribution to soil CO2 efflux indicated a substantial contribution of bacterial respiration to soil CO2 efflux within this system. There was no relationship between microbial biomass [microbial dissolved organic carbon (DOC)] and soil CO2 efflux, or root length (or mass) density and microbial biomass. This suggests that species and climatic effects on root and microbial activity drive soil CO2 efflux. As plant species within this system differed in their association with mycorrhizal fungi and had a strong effect on the individual components of soil CO2 efflux, we conclude that shifts in vegetation cover and growth and the response of vegetation to long term warming and potential future extreme precipitation events (e.g., large preciptation events, prolonged drought) will be major drivers of changes in soil carbon (C) dynamics and associated soil CO2 efflux.

This thesis explores the chemical contents of post oak and willow trees. Samples of each tree are compared to determine the amount of sulfur, phosphorus, potassium, sodium, silicon, iron, aluminum, calcium, magnesium, and manganese in them. Results indicated usefulness of each tree to humans.