A restored elk (Cervus elaphus) population in eastern Kentucky may be affecting ecosystem processes in a landscape composed of reclaimed grassland expanses and isolated forest remnants. Elk routinely select forested ridge-tops as resting and ruminating sites. These locations are characterized by sparse or absent leaf litter, trampled and diminished vegetation, large deposits of dung, and urine-saturated soils. In fall 2003, a series of fenced ungulate exclosures were constructed; 8 on highly disturbed forested ridge-tops and 8 on reclaimed grasslands. Soil analyses measured % moisture, pH, total nitrogen, total carbon, ammonium, nitrate, phosphorus, and major extractable cations in 0-10 cm and 10-20 cm cores. Litter depths and percentages of bare ground, vegetative cover, litter cover, and woody debris were measured. Sediment and water samples were collected monthly from sediment traps on reference and experimental ridge-tops. Studentfs t-tests were used to determine significance (p . 0.10) between treatments. Disturbed ridge-tops had higher soil ammonium (0.68 mg/kg, 10-20 cm) than reference sites (0.25 mg/kg) in spring 2004 and lower ammonium (0.72 mg/kg, 0-10 cm; 0.44 mg/kg, 10-20 cm) than reference sites (1.80 mg/kg, 0-10 cm; 0.94 mg/kg, 10-20 cm) in summer 2004. Total carbon was higher inside (67.57 g/kg, 0-10 cm) than outside (45.38 g/kg) of ridge-top exclosures in fall 2004. Soil moisture, litter depths, and vegetative cover were generally lower, while % bare ground was higher on disturbed ridge-tops. Sediment collected from traps averaged 2.21g/m2 inside exclosures, 2.86 g/m2 outside exclosures, and 0.39 g/m2 on reference ridge-tops. These data suggest that this reintroduced species is changing several attributes of the Cumberland Plateau landscape. The lack of a predator such as the gray wolf (Canis lupis) or cougar (Puma concolor) likely contributes to the development of habitual elk use of landscape features such as remnant ridge-top forests. Such concentrated use may create conditions for the colonization of certain plant species including rare natives and invasive exotics. Continued monitoring of high use areas is recommended so that managers can fully understand the long-term impact of the return of this large, gregarious herbivore, and that appropriate management actions can be developed to promote native biodiversity.

The Lewisville Lake Environmental Learning Area (LLELA) is a wildlife management area with tallgrass prairie, an endangered ecosystem. Essential ecosystem processes, especially fire, are part of restoration. To support fire management efforts at LLELA and surrounding areas, this project evaluated and developed tools for fire restoration. The four primary prairie grasses respond favorably to burning. Fuel loads and fuel models vary by scale and survey method. One- and 10-hour fuel moisture can be predicted using a statistical model; 100- and 1,000-hour fuel moisture cannot. Historic weather data suggests that burning can occur when it is most effective. The production of ozone precursors produced by burning is comparable to those emitted every six minutes by regional automobiles.

<p>Climatic variation and change affect the dynamics of organisms and ecosystem processes. This thesis examines phytoplankton as a target variable to trace climatic impacts on Lake Erken (Sweden) with special emphasis on the spring bloom. </p><p>A strong correlation between the timing of the spring bloom and the North Atlantic Oscillation (NAO) illustrates the link between atmospheric pressure variations and local biological processes. The predictive power increased by applying a recently established regional Scandinavian Circulation Index (SCI). Changes to an earlier timing of the spring bloom and elevated water temperature were induced by the global warming trend. The climate signal was still persistent in summer manifested by an enhanced summer phytoplankton biomass. </p><p>Between spring and summer, the phytoplankton was mainly controlled by phosphorus limitation. The application of a new method to measure alkaline phosphatase activity revealed that P-limitation varied between species and among individual cells.</p><p>Combining the above knowledge and literature data, the impact of the NAO on the timing of life history events, biomass and trophic cascade in aquatic and terrestrial ecosystems was quantitatively tested with a meta-analysis. In all environments, pronounced effects of the NAO were apparent, indicating the generality of climate effects found in different ecosystems. </p><p>Finally, a regional climate model was applied, forcing a physical lake model from which future lake conditions were simulated. The simulation revealed a one-month shorter ice cover period with two years out of ten being completely ice free. Internal eutrophication is one of the expected consequences. </p><p>In conclusion, the strong influences of global and regional climate are apparent in local physical, chemical and biological variables and will most probably also in future affect the structure and function of processes in lakes. </p>

Climatic variation and change affect the dynamics of organisms and ecosystem processes. This thesis examines phytoplankton as a target variable to trace climatic impacts on Lake Erken (Sweden) with special emphasis on the spring bloom. A strong correlation between the timing of the spring bloom and the North Atlantic Oscillation (NAO) illustrates the link between atmospheric pressure variations and local biological processes. The predictive power increased by applying a recently established regional Scandinavian Circulation Index (SCI). Changes to an earlier timing of the spring bloom and elevated water temperature were induced by the global warming trend. The climate signal was still persistent in summer manifested by an enhanced summer phytoplankton biomass. Between spring and summer, the phytoplankton was mainly controlled by phosphorus limitation. The application of a new method to measure alkaline phosphatase activity revealed that P-limitation varied between species and among individual cells. Combining the above knowledge and literature data, the impact of the NAO on the timing of life history events, biomass and trophic cascade in aquatic and terrestrial ecosystems was quantitatively tested with a meta-analysis. In all environments, pronounced effects of the NAO were apparent, indicating the generality of climate effects found in different ecosystems. Finally, a regional climate model was applied, forcing a physical lake model from which future lake conditions were simulated. The simulation revealed a one-month shorter ice cover period with two years out of ten being completely ice free. Internal eutrophication is one of the expected consequences. In conclusion, the strong influences of global and regional climate are apparent in local physical, chemical and biological variables and will most probably also in future affect the structure and function of processes in lakes.

Acid mine drainage (AMD) is a significant environmental issue worldwide, which often causes severe contamination and marked species losses in receiving streams. However, little is known about how this stress alters food webs and ecosystem function. I conducted a literature review, which revealed that AMD-impacted streams generally had depauperate benthic communities dominated by a few tolerant species and impaired ecosystem processes. Next, using survey and experimental-based approaches, I investigated food web structure and energy flow in these highly stressed streams, which typically have low pH (< 3), high concentrations of dissolved metals (Al, Fe), and substrata coated with metal hydroxide precipitates, on the South Island, New Zealand. Inputs of AMD caused substantial loss of consumers and reduced the overall number of links between species generating small and simplified food webs, with few invertebrates and no fish. Comparative analysis of food webs from a survey of 20 streams with either anthropogenic or natural sources of acidity and metals, indicated that anthropogenic sources had a stronger negative effect on food web properties (size, food chain length, number of links); an effect driven primarily by differences in consumer diversity and diet. However, the presence of fewer trophic levels and reduced trophic diversity (detected using isotopic metrics), were common structural attributes in AMD-impacted webs along a pH gradient, regardless of impact level. Furthermore, complementary dietary analyses of consumer gut contents and stable isotope signatures (δ13C and 15N) confirmed that primary consumers fed generally on basal resources and that there were few predatory interactions, which reflected low densities of small-bodied chironomids. This suggests that food quantity was unlikely to limit primary consumers but that reduced prey availability may be an additional stressor for predators. In these radically re-structured food webs, trophic bottlenecks were generated at the primary consumer level and energy flow to higher consumers was disrupted. However, streams still retained some limited function, including slow leaf litter breakdown, which provided detrital resources and supported the small food webs. Overall, my findings have furthered our understanding of these highly stressed stream ecosystems by providing new insights into interactions among species and trophic levels that structure food webs and enable function.

With the increasing degradation of rivers worldwide, an understanding of spatial and temporal patterns in freshwater quality is important. Water quality is highly variable in space and time, yet this is largely overlooked at the scale of stream catchments. I employed a landscape ecology approach to examine the spatial patterning of water quality in complex, impacted stream networks on the Canterbury Plains of the South Island of New Zealand, with the goal of understanding how land-use effects proliferate through stream systems. In particular, I used “snapshot” sampling events in conjunction with spatial modelling and longitudinal profiles to investigate the ways in which spatial and environmental factors influence the variability of water quality in stream networks. Spatial eigenfunction analyses showed that distance measures, which took into account variable connectivity by flow and distance along the stream between sites, explained more spatial variance in water quality than traditional distance metrics. Small upstream reaches were more spatially and temporally variable than main stems (under summer base-flow conditions). The extent of spatial variation in water quality differed between stream networks, potentially depending on linkages to groundwater and the surrounding landscape. My results indicated that the water quality of headwater streams can have a disproportionate influence over water quality throughout an entire network. I investigated spatio-temporal patterns in water quality more intensively in one stream network, the Cam River, in which I found consistent spatial pattern through time. The relative balance between nutrient inputs (pollution and groundwater) and in-stream conditions influenced the spatial pattern of water quality, as well as that of several ecosystem processes which I measured simultaneously. The spatially intensive and explicit approach has allowed identification of key factors controlling water quality and ecosystem processes throughout the Cam River. This research highlights the importance of taking a spatially explicit approach when studying stream water quality and that such an approach could be insightful and will contribute to solving current stream management problems.

Root productivity likely has consequences for the composition, activity, and recovery of soil microbial populations and the belowground processes mediated by these organisms. In tallgrass prairie, ecotypic variation potentially exists in response to a strong precipitation gradient across the Great Plains. Thus, ecotypic variation within a species may differentially affect belowground net primary productivity (BNPP), the associated soil microbial community, and may scale up to affect ecosystem processes. The goals of this study were to elucidate: (1) whether ecotype, environment, or an ecotype by environment interaction regulate BNPP of a dominant species (Andropogon gerardii) collected from and reciprocally planted in common gardens across a precipitation gradient, and (2) whether variation in BNPP scales to affect microbial biomass and ecosystem processes. I quantified root biomass, BNPP (using root ingrowth bags), soil microbial biomass, and nutrient mineralization rates in root-ingrowth cores below six population sources of A. gerardii (2 Illinois, 2 eastern Kansas, and 2 central Kansas) established in southern Illinois, eastern Kansas, and central Kansas. An ecotype effect was found on above and belowground net primary productivity, but these findings did not translate to soil response variables. Microbial populations themselves may affect the productivity and composition of prairie species. In a second study, soil ecological knowledge (SEK) was tested by applying a native prairie soil slurry amendment to restoration plots to determine efficacy of this method as a restoration practice. The goals of this two year study were to elucidate: (1) whether a slurry amendment of prairie soil would increase above and belowground productivity and belowground ecosystem processes in a prairie restoration, and (2) to evaluate whether differences in plant diversity will scale to affect belowground productivity and ecosystem processes. I quantified aboveground net primary productivity (ANPP) and species composition, as well as root biomass, belowground net primary productivity (BNPP), soil microbial biomass, and nutrient mineralization rates in root-ingrowth cores installed in treated and control plots. A treatment effect was noted on root biomass and total PLFA biomass; however, there was no treatment effect on cover, ANPP, or soil microbial processes. Though the soil microbial community did represent native prairie soil, there was poor establishment of prairie plant species. These factors may be due to the limited time available for data collection and the lack of precipitation in the second growing season. Longer studies may be necessary to fully examine the effects of soil slurry amendments as restoration tools.

abstract: Non-native consumers can significantly alter processes at the population, community, and ecosystem level, and they are a major concern in many aquatic systems. Although the community-level effects of non-native anuran tadpoles are well understood, their ecosystem-level effects have been less studied. Here, I tested the hypothesis that natural densities of non-native bullfrog tadpoles (Lithobates catesbeianus) and native Woodhouse's toad tadpoles (Anaxyrus woodhousii) have dissimilar effects on aquatic ecosystem processes because of differences in grazing and nutrient recycling (excretion and egestion). I measured bullfrog and Woodhouse's carbon, nitrogen, and phosphorus nutrient recycling rates. Then, I determined the impact of tadpole grazing on periphyton biomass (chlorophyll a) during a 39-day mesocosm experiment. Using the same experiment, I also quantified the effect of tadpole grazing and nutrient excretion on periphyton net primary production (NPP). Lastly I measured how dissolved and particulate nutrient concentrations and respiration rates changed in the presence of the two tadpole species. Per unit biomass, I found that bullfrog and Woodhouse's tadpoles excreted nitrogen and phosphorus at similar rates, though Woodhouse's tadpoles egested more carbon, nitrogen, and phosphorus. However, bullfrogs recycled nutrients at higher N:C and N:P ratios. Tadpole excretion did not cause a detectable change in dissolved nutrient concentrations. However, the percent phosphorus in mesocosm detritus was significantly higher in both tadpole treatments, compared to a tadpole-free control. Neither tadpole species decreased periphyton biomass through grazing, although bullfrog nutrient excretion increased areal NPP. This result was due to higher biomass, not higher biomass-specific productivity. Woodhouse's tadpoles significantly decreased respiration in the mesocosm detritus, while bullfrog tadpoles had no effect. This research highlights functional differences between species by showing non-native bullfrog tadpoles and native Woodhouse's tadpoles may have different effects on arid, aquatic ecosystems. Specifically, it indicates bullfrog introductions may alter primary productivity and particulate nutrient dynamics. / Dissertation/Thesis / Masters Thesis Biology 2015

The role of disturbance is widely recognized as a fundamental driver of ecological organization from individual species to entire landscapes. Anthropogenic disturbances from military training provide a unique opportunity to examine effects of disturbance on vegetation dynamics, physicochemical soil properties, and ecosystem processes. Additionally, plant functional diversity has been suggested as the key to ecosystem processes such as productivity and nutrient dynamics. I investigated how disturbance and functional composition both singly and in combination affect vegetation dynamics, soil physicochemical properties, and ecosystem processes. I conducted my research at Fort Pickett, Virginia, USA to take advantage of the spatially and temporally predictable disturbance regime. In order to investigate the effect of plant functional composition on ecosystem properties, I used functional groups comprised of species with similar physiology and effects on ecosystem processes (C4 grasses, C3 grasses, legumes, forbs, woody plants). My study showed that two distinct disturbances associated with military training, vehicle maneuvers, and fire; affect functional group abundance, within functional group richness, and total species richness. I found strong effects of vehicle maneuvers on soil physical properties including an increase in bulk density and reduction in soil porosity. Fire also influenced soil physical properties but more indirectly through the reduction of above ground litter inputs. Though many of the measured physicochemical soil properties at Fort Pickett exhibited statistically significant effects of disturbance, the strength of these relationships appears to be modulated by influences of previous land use. I found statistically significant (P < 0.05) effects of disturbance on chlorophyll fluorescence, and effect of functional composition on available soil N- NH4+. In addition, I detected a significant interactive effect of disturbance class and functional composition on soil CO2 flux. The interactive effects of disturbance and functional composition on soil CO2 flux demonstrated how the loss of functional diversity could lead to instability in ecosystem processes in disturbed ecosystems.    In a dynamic ecosystem, I demonstrated that the abundance and diversity of plant functional groups was significantly influenced by disturbance. By experimentally altering the abundance and diversity of these functional groups in a disturbance-mediated ecosystem, I showed that functional groups and presumably species influence key ecosystem processes. / Ph. D.

Mining interspecies interactions remain a challenge due to the complex nature of microbial communities and the need for computational power to handle big data. Our meta-analysis indicates that genetic potential alone does not resolve all issues involving mining of microbial interactions. Nevertheless, it can be used as the starting point to infer synergistic interspecies interactions and to limit the search space (i.e., number of species and metabolic reactions) to a manageable size. A reduced search space decreases the number of additional experiments necessary to validate the inferred putative interactions. As validation experiments, we examine how multi-omics and state of the art imaging techniques may further improve our understanding of species interactions’ role in ecosystem processes. Finally, we analyze pros and cons from the current methods to infer microbial interactions from genetic potential and propose a new theoretical framework based on: (i) genomic information of key members of a community; (ii) information of ecosystem processes involved with a specific hypothesis or research question; (iii) the ability to identify putative species’ contributions to ecosystem processes of interest; and, (iv) validation of putative microbial interactions through integration of other data sources.