Temperature Interaction with Density on the Growth and Survival of a Common Generalist Butterfly

Norman Jesse Cone IV is an undergraduate student in the School of Biological Sciences at Louisiana Tech University. Natalie Clay is an Assistant Professor in School of Biological Sciences at Louisiana Tech University

Determining the Effects of Prescribed Burning on Water Quality and Soil Chemistry in a Shortleaf Pine Restoration Forest

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Nutrient availability and the structure and function of brown food webs

Understanding individual nutritional requirements can generate good predictions for how communities should be structured and how ecosystems function over gradients of nutrient availability. Aboveground consumers can shape belowground processes by serving as conduits for resources through excreta, and these nutrient pulses can profoundly impact ecosystem processes. Excreta like urine and feces is a frequently deposited source of nitrogen (N) and potassium (K), and sodium (Na) that can create enduring spatial heterogeneity in the forest floor by creating nutrient hotspots. Unlike N and K, Na is unique in that it is relatively unimportant for plants, which concentrate very little Na in their tissues, but critical for consumers, which concentrate Na well above plant levels. This results in the trophic bioaccumulation of Na. Thus, plant consumers are likely Na-limited but their predators, which consume salty prey, are likely not. Omnivores are a common trophic group, eating both plant and animal tissue, that have Na tissue concentrations intermediate between herbivores and predators; but what determines the ratio of plants:prey is not well understood. Sodium is generally abundant near oceans, but its deposition in oceanic aerosols sharply decreases to zero moving inland away from coastlines. From this framework, I made predictions about how brown (detrital) food webs should be structured and function across Na gradients from tropical to boreal forests. I added Na subsidies to a Na-poor tropical forest and used stable isotope analysis to quantify the trophic positions of brown food web invertebrates and found that microbi-detritivores rapidly and predictably recruited to short-term Na subsidies but predators did not. In coastal Na-rich Panama I found that nutrient-rich excreta in the form of ant refuse from Azteca trigona, a dominant Neotropical canopy ant that feeds on honeydew and insects and rains refuse out of its hanging nests onto the leaf litter below, was a nutritional conduit between the canopy and forest floor. Refuse enhanced decomposition and supported larger brown food webs than leaf litter without refuse. I then used synthetic urine to separate the effects of Na from urine’s other nutrients and contrasted their roles in promoting decomposition and microbi-detritivore recruitment in both a Na-poor inland Ecuadorian and a Na-rich coastal Panamanian tropical forest. I found that urine was an important source of Na in the Na-poor but not Na-rich tropical forest that attracted termites and increased wood decomposition. Lastly, I tested whether omnivores become more carnivorous in Na-poor forests across a gradient of Na availability in ten paired (inland and coastal) lowland forests from Georgia to Maine, USA and also used laboratory Solenopsis invicta colonies. Omnivorous ants were up to an entire trophic level higher in Na-poor forests compared to conspecifics in Na-rich paired forests. Sodium gradients best predicted the difference in trophic position between conspecifics, and Na-starved S. invicta colonies increased Na and prey-seeking behavior 6-fold above control colonies. My results suggest that gradients of nutrient availability such as Na strongly impact brown food web structure and function. Across these gradients foraging animals facilitate heterogeneity in these leaf litter communities by acting as nutritional conduits between aboveground and belowground systems, but the impacts of these nutrient subsidies on brown food web structure and function depend on nutrient limitations of individual organisms. Lastly, my results suggest that there is a geography of omnivory that can be partially understood as a response to gradients in Na

Input of Invertebrate Biomass following Storm Events Links Aboveground and Belowground Systems

Madison Britton and Natalie Clay are a apart of the School of Biological Sciences at Louisiana Tech University. Courtney Siegert and Katy Limpert are a part of the Department of Forestry at Mississippi State University

Effects of Low-Level Additions of Salt on Decomposition Rates and Plant Sodium Concentrations in a Southeastern, US Riparian System

Connor Gruntz is an undergraduate student in the School of Biological Sciences at Louisiana Tech University. Sally Entrekin is a faculty member in the Biology Department at the University of Central Arkansas. Michelle Evans-White is a Professor in the Department of Biological Sciences at the University of Arkansas. Natalie Clay is an Assistant Professor in the School of Biological Sciences at Louisiana Tech Universit

Effects of Low-Level Salt Additions on Plant Growth and Implications for Riparian Detrital Processing

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Bark Beetle Influence on Diversity of Leaf Litter Communities

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11. An examination of the species-area-energy relationship driving decomposer diversity within “sponge” habitats in an estuarine bay

The species-area relationship is a well-known pattern in ecology detailing a strong positive relationship between habitat area and species richness. Alternatively, the species-energy hypothesis suggests that total energy availability drives species richness, with higher richness in systems with more energy input. While these two hypotheses are difficult to separate as they are positively related, they can be mutually exclusive. Species richness may increase with both area and energy availability independently. Here we test the relative importance of habitat area vs energy availability by placing two artificial substrates, polypropylene and cellulose sponges, with four different surface areas in two estuarine habitats. Cellulose sponges are organic and therefore should increase biodiversity by providing both protective structure and nutrition, while polypropylene sponges only provide structure. Organic sponges with large surface areas should promote more diversity than synthetic sponges with the same surface area. To test this, 40 cellulose and 40 polypropylene pre-weighed sponges of each surface area were placed in salt marshes and the open ocean of Terrebonne Bay in Louisiana. After one month, organisms were removed and categorized, and dry weight of the sponges collected. Preliminary results show that abundance was negatively related to surface area, contrary to predictions. However, organic sponges lost more mass, but supported similar abundances of organisms than polypropylene sponges. These results suggest that cellulose sponges are primarily used as nutrition as their effect should be additive if used as structure as well. This project offers important insights into the complexities that habitat diversity has on decomposer systems

Exposure to the leaf litter microbiome of healthy adults protects seedlings from pathogen damage

It is increasingly recognized that microbiota affect host health and physiology. However, it is unclear what factors shape microbiome community assembly in nature, and how microbiome assembly can be manipulated to improve host health. All plant leaves host foliar endophytic fungi, which make up a diverse, environmentally acquired fungal microbiota. Here, we experimentally manipulated assembly of the cacao tree (Theobroma cacao) fungal microbiome in nature and tested the effect of assembly outcome on host health. Using next-generation sequencing, as well as culture-based methods coupled with Sanger sequencing, we found that manipulating leaf litter exposure and location within the forest canopy significantly altered microbiome composition in cacao. Exposing cacao seedlings to leaf litter from healthy conspecific adults enriched the seedling microbiome with Colletotrichum tropicale, a fungal endophyte known to enhance pathogen resistance of cacao seedlings by upregulating host defensive pathways. As a result, seedlings exposed to healthy conspecific litter experienced reduced pathogen damage. Our results link processes that affect the assembly and composition of microbiome communities to their functional consequences for host success, and have broad implications for understanding plant–microbe interactions. Deliberate manipulation of the plant– fungal microbiome also has potentially important applications for cacao production and other agricultural systems in generalIt is increasingly recognized that microbiota affect host health and physiology. However, it is unclear what factors shape microbiome community assembly in nature, and how microbiome assembly can be manipulated to improve host health. All plant leaves host foliar endophytic fungi, which make up a diverse, environmentally acquired fungal microbiota. Here, we experimentally manipulated assembly of the cacao tree (Theobroma cacao) fungal microbiome in nature and tested the effect of assembly outcome on host health. Using next-generation sequencing, as well as culture-based methods coupled with Sanger sequencing, we found that manipulating leaf litter exposure and location within the forest canopy significantly altered microbiome composition in cacao. Exposing cacao seedlings to leaf litter from healthy conspecific adults enriched the seedling microbiome with Colletotrichum tropicale, a fungal endophyte known to enhance pathogen resistance of cacao seedlings by upregulating host defensive pathways. As a result, seedlings exposed to healthy conspecific litter experienced reduced pathogen damage. Our results link processes that affect the assembly and composition of microbiome communities to their functional consequences for host success, and have broad implications for understanding plant–microbe interactions. Deliberate manipulation of the plant– fungal microbiome also has potentially important applications for cacao production and other agricultural systems in genera

Ant and Detrital Communities Impacted by Bluestain Fungi (Ascomycota: Ophiostomatoid) Inoculation in Coarse Woody Debris

Casey Morin is a graduate student in the School of Biological Sciences at Louisiana Tech University. Juliet Tang is a member of the Forest Service in the United States Department of Agriculture. Courtney Siegert is in the College of Forest Resources at Mississippi State University. Nathan Little is a part of the USDA Forest Service in the Forest Products Laboratory, in the Durability and Wood Protection department, in Starkville, MS. John Riggins is in the department of Biochemistry, Molecular Biology, Entomology, & Plant Pathology at Mississippi State University. Natalie Clay is in the School of Biological Sciences at Louisiana Tech University. To view the abstract for their presentation Ant and Detrital Communities Impacted by Bluestain Fungi (Ascomycota: Ophiostomatoid) Inoculation in Coarse Woody Debris click on the blue download button