Current Research Projects
Debunking angler lore: Can the Farmer's Almanac really forecast catch rates?Ashley Shannon, senior wildlife, fisheries and aquaculture major, examined angler catch-rates. Both environmental and social factors influence angler catch-rates, and several resources are available that claim to forecast angler success. The Farmer's Almanac "fishing calendar" predicts daily fishing conditions and, while the exact formula is unknown, the forecasts are widely accepted in popular culture. The study attempted to corroborate historic fishing conditions using creel data collected from Enid Lake, northcentral Mississippi. Catch-per-unit-effort (CPUE) as hourly catch-rates for boat anglers were calculated over three years (2006, 2010, 2014). Those estimates were then compared to the Farmer's Almanacs' predicted fishing conditions (poor, fair, good, best) using linear regression. The influence of year and fishing condition were evaluated by parameterizing models that included and excluded their effect on mean angler catch rates. Conclusions of the research suggest that local conditions and weather may influence fishing conditions, however, other abiotic factors, including water temperature, light intensity, and barometric pressure, may better predict fishing success. Until we better understand mechanisms behind fishing success, the Farmer's Almanac "fishing calendar" should not be the sole resource used by anglers seeking high catch-rates.
Evaluation of Additives and Storage Conditions on Southern Yellow Pine Energy PelletsSenior forestry major Branson Wetzstein assisted in using pelletizing additives that were interesting to various pelleting industries to determine if pelleting production could be improved along with pellet characteristics. Southern pine energy pellet production is a growing industry in the United States and supplies overseas countries with millions of dollars of materials to run industrial boilers. In recent years, the pellet industry has found that the use of additives in the pellets can help improve pellet durability, improve BTU content, and lower the energy requirement needed to create the pellets. The goal of the research is to test pellet qualities based on additives, storage temperatures, and storage inflows. In addition, additives were compared for their effect on energy cost to produce vs energy yield of the pellet. Pellets were produced using a Sprout Walden (Andritz Sprout) model 501H with a 125 HP motor. Energy content of the pellets was evaluated with an adiabatic bomb calorimeter ASTM 5373 (2013a). The electrical power consumption was measured with an Extech model 382090 3-phase power analyzer. The amount of pellets created was recorded and the amount of energy required to form the pellets was determined in terms of kWh/ton. The feed rate, the moisture of the feed falling into the pelletizer, and the resultant moisture of the pellets was found and recorded. Moisture content assessment followed the ASTM E871 standard. Overall out of three types of pellets created (control, bio-oil additive, cornstarch additive), the pellets with the cornstarch additive at 1.8 wt% required less energy to form and also had the best durability. The control had the highest energy content, however the ratio of energy content to the energy used was the lowest. The cornstarch had the highest ratio of energy content to the amount of energy used. While airflow through the barrels influenced moisture content of the pellets, the bulk density and durability characteristics did not change. Based on the findings, the bio-oil additive can improve profit margins if it can be created without extra cost; however, issues regarding durability (91.5%) will have to be addressed before commercial companies can adopt bio-oil as an additive.
Vertebrate Succession in Carrion Food WebsSuccession is the directional process of change within an ecological community over time. Carrion, or the decaying flesh of dead animals, is an important basal resource with many vertebrates specializing as scavengers, predators of scavengers, both scavengers and predators, or animals responding to plant community changes caused by carrion. However, little is known about vertebrate succession in the carrion food web as most studies only consider scavengers being affected. Emma Winterhalter, a wildlife, fisheries and aquaculture major, monitored vertebrate use of carrion with camera traps to document vertebrate succession in an undergraduate research project. In July 2016, she and fellow researchers distributed varying amounts of donated feral swine carrion in five circular 20 m2 plots at John Starr forest, Mississippi. Each plot was equipped with a camera trap taking photographs of animals using carrion. A clear pattern of vertebrate succession emerged. Scavengers (e.g. vultures, coyotes) arrived within hours and likely were eating primarily carrion. Insect abundance also increased exponentially stimulating the arrival of their predators (e.g. armadillos, brown thrashers) around five days after carrion deployment. Vertebrates that were predators and scavengers (e.g. opossums) consumed carrion and insects, and were consistently present from deployment for three months. White-tailed deer and gray squirrels, which were not consuming carcasses or insects, appeared last, well after carrion was fully decomposed. Interestingly, vertebrate succession in the carrion food web closely followed the succession of resource availability with scavengers arriving first to consume carrion, predators second to consume scavengers, scavenger/predators present for both resources, and other nonscavenger, nonpredator vertebrates responding to plant community changes after decomposition. The data demonstrates that carrion food webs extend much further than to just scavengers.
Evie Von Boeckman
Shifting Composition in Upland Oak Forests: Potential Impacts on Forest Flammability Due to Changing Fuel Moisture and Drying Rates.Senior wildlife, fisheries and aquaculture major Evie Von Boeckman studied how an increase in fire-sensitive, shade-tolerant species (mesophytes) impacts moisture content and drying rates in fuel beds, and if fuel bed wetting method (soaking, rainfall simulation, natural rainfall event) influences these response variables. Mesophytes are becoming dominant in historically fire-maintained and oak-dominated (Quercus spp.) forests in the eastern U.S. This could have large impacts on forest flammability, and thus maintenance of oak forests, if mesophyte leaf litter traits influence fuel moisture. This study hypothesized that as mesophyte contribution increases, moisture would be retained longer causing slower drying rates. We also anticipated that the natural rain event method would most closely represent the conditions leaf litter would normally experience, so differences among fuel bed types would be most distinct. To test these hypotheses, we constructed fuel beds in the lab comprised of upland oak litter (Q. stellata, Q. coccinea) and increasing amounts of mesophyte (Liquidambar styraciflua, Carya spp, Ulmus alata) litter (0%, 33%, 66%, and 100%). We wetted fuel beds by, (1) soaking for 24 hr, (2) simulating a summer precipitation event (0.0072 cm over 10 min), and (3) exposing litter to a natural winter rain event (0.19 cm over 4 hr). All treatments exhibited a rapid initial (within 4 hr) decrease of moisture followed by a more gradual decline over the 48 hr drying period; however, beds comprised only of mesophyte litter dried slowest, while those with high oak contribution (66% and 100%) dried fastest. The simulated rainfall and rain event produced similar drying rates; soaking, however, showed the highest moisture content initially and less distinction and separation between drying rates. These findings suggest that increased contribution of mesophyte leaf litter to fuel beds will increase moisture and slow drying rates, which could hinder forest flammability in upland oak systems.
Adaptation to "dishonest" environmental signals: Insights from an experimental microcosmIsabella Durham, a senior wildlife, fisheries and aquaculture major, examined fitness of individuals and populations to select quality habitat in light of changing climates. An animal's perception of these quality cues and their ability to adapt to changing cues are critical to population persistence. The influence of perception of resource quality on fitness of fruit flies (Drosophila melanogaster) was examined in an experimental system consisting of dishonest resource signals. Flies were placed on 24 diets varying in nutritional quality, and with non-nutritional quality-modifying additives, in a fully crossed design (high or low concentrations of carbohydrates, yeast, and sugar, and an attractant, repellent, or no additive [the control]). Eight generations were grown on every diet in isolation across 4 experimental trials, and fecundity counts were taken at generations 2 and 8 to assess potential adaptation. Fitness generally declined at low nutritional values as expected, though this effect diminished significantly by generation 8. In generation 2, diets with added attractant exhibited higher fecundity counts, and repellants exhibited lower counts; however, the direction of both effects switched by generation 8. Our results indicate rapid adaptation to adverse true environmental conditions, with populations increasing their fecundity by generation 8 on poor quality resources. Populations also adapted to the presence of a perceptual modifier over the same period-that is, incorrect signals of resource quality ceased to modify behavior within 8 generations of exposure. These results suggest that the rate of generational turnover is critical to population persistence in changing environments. Quickly reproducing ("r-selected") species should more quickly to adapt incorrect signals than those that reproduce slowly ("K-selected") due to decreased time necessary for adaptation to occur across generations. Animal perception and cognition are ecological mechanisms critical to population persistence in changing environments, and to establishment in novel environments (e.g., reintroduction or range expansion), with profound implications for biological invasions, conservation, and management.
Relationships Between Leaf Stomatal Properties and Whole-Tree Water Use in a Bottomland Hardwood EcosystemThe collection of physiological response data from trees can be a challenging and time-consuming task particularly in ecosystems with high species diversity. Leaf stomatal properties are more easily obtained and may inform forest water use and productivity models if they exhibit enough correlation with physiological functioning. Forestry major Justin Yow compared stomatal properties across various tree species from three plant families growing in a bottomland forest to determine if stomatal properties correlate with physiological functioning. Sapflow was measured in seven hardwood species (American elm, winged elm, shagbark hickory, willow oak, water oak, cherrybark oak and swamp chestnut oak) using heat dissipation sensors. Vapor pressure deficit (VPD), soil moisture, and photosynthetically active radiation (PAR) were monitored simultaneously. Seasonal water use per unit leaf area and relationships between daily water use and environmental parameters were estimated to determine the response of sapflow to environmental drivers. Leaves were collected from tree canopies at the end of the growing season. Epidermal peels were made and analyzed to quantify stomatal density and length.
Among species, stomatal density varied significantly, with American elm having a significantly lower density than all the oaks. Shagbark hickory also had a significantly lower stomatal density than all oak species except water oak. Across all tree species, stomatal density had a significantly negative correlation with seasonal water use per unit leaf area and daily sapflow responses to VPD and PAR. These results show that in an area of rich tree species diversity density measurements tended to be similar within tree families but significantly different across families. Based on these findings, stomatal parameters may be used to predict seasonal water use per unit leaf area and responses of water use to environmental parameters across tree species to increase understanding of relationships between leaf structure and physiological functioning.
Does sampling more than one increment core in growth-index-ratio-based stand table projection improve forest yield prediction precision?Senior forestry major Leah Leonard conducted research to investigate whether sampling more than one tree for previous diameter growth measurement significantly improves the precision of forest yield predictions from stand table projections. Obtaining future forest yield is not a straightforward process in comparison to obtaining current yields, which can be measured directly in the field. Stand Table Projection (STP) is one of the approaches of predicting future yields of forest stands. STP is simple to apply because it only requires previous diameter growth measurements from a sample of the trees in the stand, which can be measured from increment cores taken from the sample trees. Usually, one increment core is sampled per tree dbh class. One increment core may not be a good representation of a dbh class due to possibility of various measurement and growth ring formation issues. Thus, taking more than one increment core per tree dbh class may help minimize the effect of increment core measurement errors on yield predictions from STP. Individual tree measurements from 364 longleaf pine research plots in the Southeastern United States were used to investigate whether sampling more than one tree per tree size class, for previous diameter growth measurements, would significantly reduce future yield prediction errors from STP. Findings from the research indicated that sampling more than one tree per dbh class, for STP increment cores, may not result in lower STP prediction errors. In addition, it was observed that STP prediction errors for stands that were less than 50 years old were more than 2 times larger than the errors for stands that were older than 50 years.
Evaluating stand density relationships in mixed species forests of the Mississippi river flood plainBottomland hardwood (BLH) forests are ecologically and economically important resources in
floodplains of the southeastern US. Management of these forests can be challenging due to variation in species composition and site characteristics. One of the main tools available to the BLH forester is density management (i.e. "thinning"), with stocking guides being a common quantitative tool used to guide density management decisions. The current BLH stocking guide was developed based on expert opinion rather than empirical data, and is applied to a wide range of BLH forest types. This could be problematic as different species mixtures likely have different growing space requirements and thus carrying capacity, represented as maximum density, may vary between different forest types. Forestry major Mark Porter used data from the US Forest Service Forest Inventory and Analysis program and peer-reviewed literature to evaluate differences in relative stocking among several common forest types in the Lower
Mississippi flood plain. He assessed the maximum relative density by simple linear regression of
plot level data, in addition to evaluating the upper and lowers bounds of desirable stocking based on methods used in hardwood stocking guides developed in other regions. More specifically, for lower bounds he evaluated the minimum number of trees of a given size required to achieve crown closure, which is where trees start competing for growing space. Preliminary results on lower bound stocking support the hypothesis that different species will achieve crown closure at different stocking levels. These findings should provide guidance to managers about density management in forest types of different species composition to meet desired stand structural characteristics. Also, by improving knowledge of density relationships related to species composition, this study should help in the design of mixed-species afforestation efforts aimed at restoring floodplain forest cover in the southeastern US.
Removing the Adhesive Layer of Gulf Killifish (Fundulus Grandis) Eggs to Increase the Number of Eggs Available for CollectionMatthew Virden, a senior in the Department of Wildlife, Fisheries and Aquaculture, studied improved production of Gulf killifish. Killifish are intertidal spawners found in estuaries in Northeast Florida and along the northern coast of the Gulf of Mexico. There is a high demand for Gulf killifish from bait shops and anglers for use as live bait for sport fishes. This demand has led to a shortage in the overall supply of Gulf killifish, creating an increased interest in production. Adult killifish enter interior marshes during spring high tides to spawn by laying eggs in marsh grasses. The eggs have an adhesive layer, allowing them to stick to the vegetation for incubation until the next high tide. Hatching occurs once the eggs are re-submerged. While this adhesive layer is beneficial in their natural habitat, it makes it difficult to collect the eggs off spawning mats in recirculating aquaculture systems. Currently mats are shaken or tapped against a mesh screen; however, clumps of eggs are still visible within the mat. Studies were performed to assess different treatments to remove the adhesive layer to increase the number of eggs available for collection. Gulf killifish eggs were collected on 20 X 10 cm (8" X 4") Spawntex mats that were placed 8-20 cm below the water's surface in 9-3600 L recirculating aquaculture systems. Individual mats underwent randomized treatments and there was a total of nine treatments with three replicates each. Treatments consisted of 2g urea, 3g urea, 4g urea, 500 mg L-1 tannic acid, 1000 mg L-1 tannic acid, 1500 mg L-1 tannic acid, 12g cow's powdered milk, 24g cow's powdered milk, and 8ppt water. The removal efficiency for all treatments were slightly higher than the control. The three urea solutions were the only treatments that were significantly different from the control. Survival and hatching rates did not show any relation to treatments, but this could be the cause of inadequate sample size. Future studies should focus on increasing sample size and focusing on fewer solutions.