Thesis (M.S.)--University of Wisconsin--Madison, 1999. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.Sc.)(Botany)--University of Pretoria, 2006. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

AN ABSTRACT OF THE THESIS OF LEWIS KENNEDY REED, for the Master of Science degree in PLANT BIOLOGY presented on October 30, 2009, at Southern Illinois University Carbondale TITLE: COMPETATIVE EVQUIVALENCY OF CULTIVAR AND NON-CULTIVAR DOMINANT GRASSES IN AN EXPERIMENTAL RETORATION MAJOR PROFESSORS: Dr. Sara G. Baer and Dr. David J. Gibson Multiple population sources of species for use in prairie restoration exist, including cultivars and non-cultivars of dominant native grasses. However, little is known about the competitive equivalency of different population sources of dominant C4 grasses and whether intraspecific variation in their competitive effect on the community scales to affect ecosystem assembly. In 2006, an experimental restoration was established in a former agricultural field using cultivars and non-cultivars of the dominant grasses (Andropogon gerardii, Sorghastrum nutans, and Schizachyrium scoparium) and two different species pools of non-dominant species containing equal richness and distribution of species among functional groups. I evaluated inter - and intra-specific variation in the competitive equivalency of A. gerardii, S. nutans, and S. scoparium in terms of community response to their individual and complete (all three species) removal. Removals were maintained for two growing seasons, though little maintenance was needed after the initial treatment. The competitive effect of each grass species and population source was determined by calculating a response ratio for percent cover and above ground primary productivity between removal and control plots for each dominant grass individually, forbs, non-dominant grasses, and legumes which were each analyzed using a mixed model procedure for a split-split-plot randomized block design. Effects of removals on overall community composition were assessed using non-metric multi-dimensional scaling (NMDS) and analysis of similarity (ANOSIM). In addition I monitored changes in photosynthetically active radiation (PAR) at the soil surface and inorganic soil nitrogen. Based on the 2008 data (after two years of maintaining removals), several important differences were detected between the focal species and in some cases the two sources of the same species in terms of their effects on neighbors, inorganic soil nitrogen, and PAR. Many of these differences depended on which species pool the comparison took place in. A 3-way interaction was detected between species pool, source, and removal treatment in the volunteer forb group (F3, 60 =3.28, p = 0.0268). Volunteer forbs showed a positive response to removal of cultivars of the dominant grass functional group in one species pool but not the other. A three-way interaction was detected between species pool, source, and removal treatment in terms of Bray-Curtis similarity (F3, 60 = 2.91, p = 0.0417). Within one of the species pools, similarity values of communities were higher between removals and controls in cultivar plots than in non-cultivar plots where A. gerardii was removed. While NMDS ordination showed separation of some plots by dominant grass source, within group variation was higher than among group variation and ANOSIM deemed this separation insignificant. Planted forb ANPP exhibited a significantly negative response to removal of S. nutans that was not observed in the other removal treatments (F3,41.1 = 3.09, p = 0.038) suggesting facilitation by the dominant grass on planted forbs. The aboveground net primary productivity (ANPP) of the subordinate community (i.e. all species except the dominant grasses) exhibited a 3-way interaction among species pool, dominant grass source, and species removed (F3,61 = 2.76, p=0.0499). This interaction resulted from a stronger negative response of subordinate community ANPP to cultivars of the dominant grass functional group removal than non-cultivars of this group that only occurred in one of the species pools. There was a significant main effect of species removed on %PAR at ground level (F3, 60 = 4.84, p = 0.0044). All removal treatments allowed higher penetration of PAR to ground level, with S. nutans and all dominant grass removal having the strongest effect. Inorganic N availability was lower in response to removal of A. gerardii cultivars compared to the removal of non-cultivars of this species in one species pool but not the other. Removal of cultivar S. scoparium lead to a positive response in total inorganic nitrogen while removal of non-cultivars of this species lead to a negative response in total inorganic nitrogen in this same species pool (F3, 51 = 3.61, p = 0.018). Results demonstrate that inter- and intra-specific variation among these dominant species affect some aspects of community structure and ecosystem properties, but these effects are not consistent among dominant species and among subordinate species pools. These complex interactions may have important implications for restoration and land management.

The grassland bird-community has declined significantly in abundance and diversity in Illinois over the past century. Reclamation of surface coal-mines in southern Illinois has created ca. 50,000 ha of grassland habitat that offers surrogate habitat for grassland and shrubland birds. Much of the grassland habitat created by reclamation of mine lands has not been managed and has succeeded to shrubland habitat dominated by both native and non-native shrubs. The purposes of this research were to identify the bird community utilizing reclaimed surface-mines in southern Illinois, and to examine the habitat-associations of the bird community and compare those to previously reported habitat-associations. I examined bird communities, plant structure and composition, and invertebrate communities at grasslands and shrublands at 3 reclaimed surface-mines in southern Illinois. I used 100-m wide strip-transects to survey the bird community and measured habitat characteristics including: vegetation height and density, litter depth and cover, shrub density and height, and plant composition. I observed 57 bird species over 126 surveys in 2008 and 2009. I used Generalized Linear Models and Akaike's Information Criteria to develop habitat-association models for 7 bird species: Henslow's sparrow (Ammodramus henslowii), grasshopper sparrow (Ammodramus savannarum), eastern meadowlark (Sturnella magna), dickcissel (Spiza americana), indigo bunting (Passerina cyanea), field sparrow (Spizella pusilla), and Bell's vireo (Vireo belli). Of these 7 species, dependable models were found for the Henslow's sparrow, grasshopper sparrow, eastern meadowlark, and field sparrow. The best habitat model for Henslow's sparrows indicated a positive association with % litter cover and a negative association with large variations in grass cover. The best habitat model for grasshopper sparrows indicated a negative association with both litter cover and depth and a positive association with grassland area. The best habitat model for the eastern meadowlark indicated a negative association with visual obstruction and shrub density. The best habitat model for the field sparrow indicated a curvilinear association with shrub density and visual obstruction. The habitat-association model for Henslow's sparrows differed from previous research in that neither vegetation height nor density were indicated as important habitat characteristics. To identify the habitat characteristics that have the greatest effect on the overall bird-community composition, I generated graphical ordinations using non-metric multidimensional scaling. The habitat factors most affecting the bird community composition were: vegetation density, vegetation height, litter depth, shrub density, shrub height, warm-season grass cover, and the ratio of habitat area to perimeter. Invertebrate biomass at a site was positively correlated to forb cover and plant richness and negatively correlated to grass cover. Grassland bird species have distinct habitat-associations that allow them to reduce interspecific competition through niche partitioning and would be best managed with a diverse set of successional stages.

Master of Science / Department of Biology / Lydia H. Zeglin / Anthropogenic actions have significantly increased biological nitrogen (N) availability on a global scale. In tallgrass prairies, this phenomenon is exacerbated by land management changes, such as fire suppression. Historically, tallgrass prairie fire removed N through volatilization, but fire suppression has contributed to increased soil N availability as well as woody encroachment. Because soil microbes respond to N availability and plant growth, these changes may alter microbial composition and important microbially-mediated functions. Grassland management affects the soil environment on multiple time scales including short (fertilization or fire event), seasonal (growing vs. non-growing season), and long-term (decadal plant turnover and nutrient accumulation), therefore my goal was to understand community variability at different time scales affecting the population and community dynamics of soil microbes. I predicted soil microbes would be sensitive to environmental changes at all time scales, seasonal variation would reflect increased plant rhizodeposit-supported populations during summer and decomposers during winter, and long-term fire suppression and chronic fertilization would drive soil microbial community turnover associated with accumulation of plant litter and N. To address these predictions, soils were collected from the Belowground Plot Experiment (BGPE) at Konza Prairie Biological Station: a 30-y factorial field manipulation of N fertilization and burning. Surface soils (0-15 cm) were sampled monthly between Nov 2014 – Dec 2015, including one week post-fire (April) and post-fertilization (June). Genomic DNA was extracted from each sample for qPCR and PCR for Illumina MiSeq library sequencing of the prokaryotic 16S rRNA gene and fungal ITS, to estimate population and community dynamics of soil microbes. Soil environmental characteristics and plant communities were measured in July 2015 to evaluate correlations between plant and microbial communities, and environmental variability. Soil microbial responses to short-term fire/fertilization events were minimal, while microbial population sizes fluctuate seasonally and synchronously, and microbial community composition varied more with management history than at shorter time scales. Bacterial populations increased 10x during growing-season plant rhizodeposition, while fungal populations were less dynamic, but decreased in fall, possibly reflecting a shift to subsistence on soil organic matter. In contrast, microbial community composition was seasonally stable, but distinct between long-term management treatments, which may indicate accumulation of niche-defining plant or soil properties over decades. Prokaryotic communities responded to altered N availability via both fertilization and loss due to fire, with the highest abundance of "copiotrophic" (r-selected) taxa in unburned, fertilized soils. Fungal communities responded to N fertilization with higher abundance of arbuscular mycorrhizal fungi, pathogens, and saprotrophs, possibly due to changes in nutrient stoichiometry and litter availability in fertilized plots. However, fungal response to fire was largely independent of N availability, and plant community differences were correlated with fungal, but not bacterial, community composition, highlighting the likely nutritional codependence of fungi and plants, and fungal competitive advantages for plant litter substrates. The timing of changes in soil microbial communities is critical for plant nutrition and nutrient cycling in prairies, and this novel dataset on the temporal resolution of microbial responses to environmental variability contributes to the broader understanding of ecosystem responses to global change.

Doctor of Philosophy / Department of Biology / Brett K. Sandercock / Grasslands are among the most rapidly declining ecosystems in the world. The Flint Hills ecoregion contains one of the largest remaining tracts of tallgrass prairie, but most of the area is managed with high densities of grazing animals and frequent prescribed burns, thereby reducing variation in vegetative structure. A homogeneous landscape leads to lower diversity and abundance of wildlife species, including grassland songbirds. Patch-burn grazing management has been proposed to more closely match the historical interaction between fire and selective grazing by native ungulates. Pastures managed with patch-burn grazing have a greater variety of vegetative structure and plant species composition, and as a result, higher species diversity, abundance, and reproductive success of grassland birds. However, past work has not considered potential effects of regional variation in predation risk and rates of brood parasitism by Brown-headed Cowbirds (Molothrus ater), or annual variation in climatic conditions on the effects of patch-burn grazing management on the reproductive success of grassland songbirds. Over a six year period and at two tallgrass prairie sites, I tested the effects of patch-burn grazing on the reproductive success of three native grassland songbird species, Dickcissels (Spiza americana), Eastern Meadowlarks (Sturnella magna), and Grasshopper Sparrows (Ammodramus savannarum), as well as subsequent effects on the space use, movements, and survival of fledgling Dickcissels. I found only minor effects of patch-burn grazing on the reproductive success of grassland songbirds, supporting previous studies that show that patch-burn grazing does not have negative effects on demographic rates of grassland songbirds. Management regime did not affect densities or territory size of male Dickcissels, but bird densities tended to be higher and territories tended to be smaller on patches within the patch-burn grazing treatment that were burned in the previous year. Thus, patch-burn grazing management might benefit Dickcissel populations by providing higher quality breeding habitat in unburned patches. Last, I found evidence for a potential tradeoff between habitat selection for nests vs. fledglings of Dickcissels in some rangeland management strategies. Parents that realized high reproductive success by nesting in pastures with lower cowbird densities, produced fledglings that faced high rates of depredation by snakes and showed greater movements away from those pastures. Survival rates and movements of Dickcissel fledglings were low, especially during the first week after leaving the nest, which stresses the importance of local habitat conditions. At a larger spatial scale, I tested whether regional differences in habitat structure could drive variation in apparent survival of grassland songbirds. I found that grassland- and shrubland-breeding species had higher estimates of apparent survival than forest-breeding species, contrary to the prevailing viewpoint that birds breeding in dynamic landscapes, such as frequently burned grasslands, should show lower apparent survival than species that breed in woody habitats. The results of my field study show that restoring the historical interaction between fire and grazing on the landscape via patch-burn grazing management could benefit grassland songbirds. Moreover, my dissertation is the first study that tests the effects of patch-burn grazing management on the survival and movements of fledgling Dickcissels, and shows that high cowbird densities can cause a tradeoff between different life-stages. Future conservation efforts should take into account regional variation in species abundance, predator community composition and abundance of Brown-headed Cowbirds when assessing the effects of rangeland management on the demography of grassland songbirds.

Nitrogen deposition to adjacent grassland and forested areas in the vicinity of Sabie, Mpumalanga, South Africa was studied. Total deposition amounts to the forested area are calculated to be 7l.2 kg N ha-1 yr1 and to the grassland area, 25 kg N ha· 1 yr1. The average deposition amounts are similar to or at least approach nitrogen mineralisation amounts at nearby sites of 50-70 kg N ha-1 yr1. The deposition amounts are made up of 21.4 kg N ha-1 yr1 dry deposition, 7.8 kg N ha-1 yr1 wet deposition and 42 kg N ha-1 yr1 cloud droplet deposition for the forest. For the grassland, the amounts are 7 kg N ha-1 yr1 dry deposition, 7.8 kg N ha-1 yr1 wet deposition and 10.5 kg N ha-1 yr1 cloud droplet. deposition. For both wet and cloud droplet deposition, the amount attributable to nitrate was greater than that attributable to ammonium. For wet deposition, nitrate contributed 4.1 kg N ha-1 yr1 and ammonium contributed 3.7 kg N ha-1 yr1 to both forests and grasslands. For cloud droplet deposition to forests, the amounts were 28 kg N ha-1 yr1 attributable to nitrate and 14 kg N ha-1 yr1 attributable to ammonium. For grasslands the amounts were 7 and 3.5 kg N ha-1 yr1. In both forests and grasslands, the component of dry deposition contributing the most to deposition was ammonia gas, the amounts being 14.2 and 4.3 kg N ha-1 yr1 respectively. Nitric acid contributes 3.7 and 1.9 kg N ha-1 yr1 respectively and is followed by the nitrogen dioxide component that contributes 1.6 and 0.5 kg N ha- I yr1. Ammonium and nitrate particles contribute the least to deposition. For the forests the amounts are 1 and 0.9 kg N ha-1 yr1 and for the grasslands they are 0.2 and 0.1 kg N ha-1 yr1. A strong seasonal variance in deposition amounts is apparent with maximum deposition amounts occurring in Summer and minimum amounts in Winter. Intermediate amounts are deposited in Autumn and Spring, with the latter season having slightly larger deposition amounts. The seasonal variance is strongly linked to the seasonal rainfall and cloud droplet deposition patterns. Biomass burning is indicated as a possible important factor in influencing the chemical composition of rainfall during Spring. Of the deposition amounts obtained in this study, the deposition from cloud droplets is high compared to other studies and is probably overestimated. Further research into this area is needed.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, in fulfilment of the academic requirements for the degree of Doctor of Philosophy. May 2016 Johannesburg / This thesis reveals previously unknown facts concerning the invasion, ecology and management of the perennial alien forb Campuloclinium macrocephalum (Less.) DC. (Asteraceae, pompom weed) in the grassland biome of South Africa. All these areas of research are of critical importance to identify the causes of invasion and prescribe best management practises aimed at reducing the density and spread of the weed and restoring these ancient grasslands. Grassland biomes throughout the world are receiving international attention because of their vulnerability to transformation, a history of ignorance regarding their evolution and prejudice as evidenced by their exploitation. There are many theories as to why alien plants become invasive outside of their native range but most are controversial, except those that support the absence of natural enemies as the primary reason for invasiveness. Few studies have attempted to empirically measure environmental and ecological factors that facilitate invasion, not to dispute the Absence of Predators Hypothesis (APH); APH regulates invasiveness but the external factors affecting habitat vulnerability to invasion remain unchanged. Based on the assessments of 80 invaded grasslands in Gauteng Province prior to the release of any host-specific biocontrol agents, it was concluded that C. macrocephalum favours disturbed grasslands. Numerous agencies of disturbance were identified; the most important being heavy grazing, abandonment (e.g. old lands) and modification (e.g. draining of wetlands). Herbivory by generalist insects was insignificant. The main drivers of native species composition in the invaded study sites were rainfall, topography and soil texture. The weed was most problematic in grasslands with a basal cover of <19% and in poor condition from a pastoral perspective. Other alien and native invasive species were also found in grasslands with C. macrocephalum. High fire frequency also appeared to exacerbate weed density. The Novel Weapons Hypothesis postulates that some invasive species transform vegetation for establishment, densification and expansion because they are allelopathic. Stems and leaves of C. macrocephalum have both rigid multicellular hairs and glandular trichomes that exude an unidentified substance. It has been speculated that allelopathy may be an important trait aiding its rapid expansion in invaded grasslands. The importance of allelopathy and competition was investigated under controlled conditions using Eragrostis curvula (perennial grass), E. tef, (annual grass) and Lactuca sativa (lettuce) as test species. Petri-dish studies proved that root and shoot extracts of adult C. macrocephalum plants had zero inhibitory effect on the seed germination in all three test species. Stunting of radicles was evident in treatments comprising leaf extracts at 10 and 25% w/v; with E. tef displaying a higher tolerance than E. curvula. Eragrostis curvula, because it was the most sensitive of the test species, was used in a pot study together with C. macrocephalum to evaluate allelopathy and interference. The biomass and growth of E. curvula was not affected by C. macrocephalum at densities of one or five plants per pot. The weed on the other hand incurred density-dependant trade-offs in size, biomass and mortality. In a separate pot study, the incorporation of weed residues into the potting medium had no impact on the growth of E. curvula. The process went one step further by analysing the association between E. curvula and C. macrocephalum from the 80 grassland assessments. Eragrostis curvula had a narrower ecological niche and was only found in disturbed grasslands on well drained soils. Campuloclinium macrocephalum invaded a broad gradient of soil types including poorly drained wetland soils not amenable for E. curvula. Competitive exclusion between the two species was not apparent. Pot studies and field observations support a degree of tolerance between C. macrocephalum and E. curvula that lends support to coexistence at a range of weed densities. The conclusions from this study were (a) C. macrocephalum is not allelopathic and allelo-chemistry cannot be inferred as a causal mechanism for the weed’s invasiveness, and (b) C. macrocephalum and E. curvula have different limiting resource requirements that enables coexistence in areas where the latter can grow. In 2006 C. macrocephalum infestations in Gauteng Province were severely damaged by Puccinia eupatorii Dietel (Pucciniaceae), a biotrophic rust identical to the P. eupatorii strain in quarantine that was imported into South Africa from Argentina as a potential biocontrol agent. An investigation of the rust’s impact on C. macrocephalum was carried out in the 80 rangeland infestations previously assessed and how pathogen pressure affected the weed’s realised niche. The rust caused premature senescence of the stems in late summer with compensatory regrowth in autumn. In contrast disease-free plants senesced in late autumn; the rootstocks remained dormant throughout winter and did not produce compensatory regrowth. No significant changes in weed density were detected and C. macrocephalum retained its realised niche. The weed remains adapted to the rust despite a 40-year separation from the pathogen. Registered herbicides should provide 80% control of the targeted plants, providing label directions concerning concentration, mixing, application and environmental considerations are adhered to. Herbicide trials were conducted at two contrasting sites in Gauteng, a wetland and a rocky grassland, to test the efficacy of picloram and metsulfuron-methyl on the control of C. macrocephalum. Both sites had dense infestations of C. macrocephalum at the beginning of the study in 2005. Herbicides were applied in either February (summer) or April (autumn) annually for three consecutive years. Monitoring continued for an additional three years after spraying was terminated. Puccinia eupatorii established at both study sites from the second year of study. Both sites also experienced wildfires and drought. As these uncontrolled factors were not anticipated in the design their individual effects could not be factored out. Mean mortality however was <80% expected of registered herbicides which can only be attributed to uncontrolled factors acting as natural constraints. The efficacy of picloram was not significantly different (P<0.05) to that of metsulfuron methyl within a season. Autumn applications are not recommended because rust damage on the leaves is too advanced to ensure adequate herbicide uptake and translocation. Herbicide persistence in the topsoil was not detected by gas chromatography. Three applications of herbicide were inadequate to bring C. macrocephalum under control in plots. It is estimated that five to seven years of herbicide application are needed to reduce the weed density to <1 plant per plot (25 m2). This effectively renders chemical control in medium to dense infestations uneconomic. Chemical control of C. macrocephalum will only be effective if there is a commitment to follow-ups and remedial vegetation management practices. The herbicide trials also looked at the impact of picloram, metsulfuron methyl and hoeing on native species and other alien species that occurred in plots. Three plant functional groups were analysed, namely native grasses, native forbs and alien broadleaf species. The herbicides were applied as broadcast sprays over three years and therefore their effect on all broadleaf species was non-selective. Hoeing twice a year for three years only targeted C. macrocephalum. High forb richness coupled with low abundance and patchy distribution meant there was a high turnover between replicate plots across the study sites. Herbicides had a significant impact on the native forb functional group compared to hoeing which had a superficial effect. Hoeing did not suppress C. macrocephalum. The parasitic forb Thesium utile was killed in all treatments except the untreated control. The target-specific hoe treatment also eliminated T. utile, suggesting a new association might exist between parasite and C. macrocephalum. Hoeing also facilitated the establishment of alien annual weeds. In South Africa the grassland biome is under considerable threat from mining, afforestation, agriculture and urban development. Although alien plants pose a minor threat in contrast to these land-transforming activities they remain the greatest threat to grasslands that are not threatened by exploitation. Campuloclinium macrocephalum is not a pioneer species, but rather a long-lived perennial herb with evolutionary adaptations to fire, herbivory and disease. These characteristics have enabled it to establish and spread in grasslands that have been maintained in a variety of disturbed states by a range of agencies that reduce grass basal cover and exacerbate soil erosion. Addressing poor land use practises that foster C. macrocephalum invasion and spread are as important as the remedial activities necessary to control the species. Grassland restoration/rehabilitation practises have not been investigated in the context of C. macrocephalum management and is of critical importance to the integrated control of the weed. Although comprehensive literature about C. macrocephalum have recently been published gaps in our understanding of its biology, ecology and control still exist that prevent the development of best management practices. These areas for new research make ideal projects for post-graduate students. Future research should focus on (a) rust–herbicide interactions, (b) fire and seedbank dynamics, (c) integrated weed management incorporating biological control, fire, selective herbicide application techniques (e.g. spot-spraying) and ecosystem restoration practises. Grazing strategies promoting grass species adapted to frequent non-selective defoliation restrict pompom weed better than degraded underutilised rangelands, as evidenced by low levels of C. macrocephalum in communal areas, and warrants further investigation, including fence-line contrasts in invaded and un-invaded road reserves.

Tallgrass prairie is one of the most threatened grasslands in North America. Conservation of tallgrass prairie focuses on both effective management of remaining native prairie, and restoration of formerly cultivated fields to tallgrass prairie. This research focused on processes and properties relevant to restoration and conservation of tallgrass prairie. Community assembly theory attempts to explain the formation of communities, which can be governed by deterministic or stochastic processes, or some combination of both. Fire and grazing are widely used to manage grasslands for conservation purposes, but few studies have evaluated the effects of these drivers on the conservation value of plant communities measured by the floristic quality index (FQI). Pollination services play a vital role in the reproductive stability of the plant community in prairies, though this has not been well studied in restored prairie. The first chapter of this dissertation reports on a sequential restoration approach used to gain insights into the extent to which community assembly is deterministic and stochastic events change the trajectory of community development. The sequential restorations consisted of former agriculture fields restored to prairie, varying only in time since abandonment. Species composition and aboveground net primary production were quantified over time in sequentially restored communities to reveal the predictability of ecological restoration in producing desired communities and ecosystem functions. The sequential restoration plots were established in a block design. The same suite of species was seeded using the same seeding rates in each restoration sequence. Species composition was recorded each September in the year of seeding and each June and September in the two subsequent years for each block. Annual aboveground net primary productivity was collected from 2 randomly placed 0.1 m2 plots per subplot during peak biomass. There was a significant sequence by age interaction for sown, volunteer, and total species composition. Sown, volunteer, and total cover, diversity, and richness also were affected by a sequence by age interaction. Annual net primary production (ANPP) also was affected by a sequence by age interaction for sown and volunteer species. However, total ANPP was only affected by the variable age. Results show that interannual climate variability (specifically growing season precipitation) inhibits a priori determinations of community assembly, which suggests that stochastic processes play a significant role in the community assembly process in tallgrass prairie restoration. Variations in annual precipitation during the installation years likely drove the initial differences in species composition and ANPP. In general this study revealed that drought conditions at the time of restoration may be more deleterious than drought conditions occurring at other times post-establishment. The influence of fire and grazing on soil properties and functions is difficult for land managers and restoration practitioners to assess. Therefore, the objectives for the second study were to (i) to quantify the independent and interactive effects of grazing and fire frequency on floristic quality in native tallgrass prairie, and provide potential benchmarks for community assessment, and (ii) to explore whether floristic quality can serve as an indicator of soil structure and function for more holistic ecosystem assessments. A factorial combination of fire frequencies (1-2, 4, and 20 y return intervals) and grazing (by bison or ungrazed) treatments was sampled for plant species composition and several indicators of soil quality in lowland tallgrass prairie. Floristic quality, diversity, and richness were higher in grazed than ungrazed prairie over all fire frequencies. Available inorganic N, microbial biomass N, total soil N, and soil bulk density were also higher in grazed prairie soil over all fire frequencies. Microbial biomass C, total soil organic C, and total soil N were positively correlated with FQI. This study demonstrated that floristic quality and soil N pools are more strongly influenced by grazing than fire and that floristic quality can be an indicator of total soil C and N stocks in never cultivated lowland prairie. In tallgrass prairie, 85 – 90 % of angiosperms require an insect or other animal for pollen transfer. Restorations can play a vital role in the reestablishment of pollination services and simultaneously help maintain high levels of diversity in the tallgrass prairie ecosystem. Missed pollination, via temporal asynchronies, could have a number of biological disadvantages for a plant population. In the third study we addressed the effects of missed pollination on floral period, photosynthetic activity, leaf N content, and seed set in a common native tallgrass prairie forb, Penstemon digitalis. In each of 12 plots, 6 individual plants were either bagged to prevent pollination, or left unbagged, to allow for pollination. There was no difference in mean flower duration between netted and open plots. There was a treatment by time interaction for relative chlorophyll concentrations (P = 0.0005). Mean relative chlorophyll concentrations values at sampling times (prior to flowering; Pre, 10 days after FFD; Plus, 10 days after cessation of flowering; Post, and at the time of leaf collection; Coll) all differed from one another in bagged plots. Comparisons of relative chlorophyll concentrations values only showed a difference between bagged and open-pollinated plots at sampling time ‘Coll’. There was no difference in percent leaf N between bagged and open-pollinated plots and the amount of seed set in bagged plots was significantly lower than the amount of seed set in the open-pollinated plats. Any disruption to plant-pollinator interactions can create temporal asynchronies, however, the impact of those asynchronies is equivocal.

Periodic disturbance in CP33 habitat buffers is required to maintain early-successional plant communities for grassland birds. However, effects of disturbance on habitat suitability and nesting success of grassland birds are unknown. Furthermore, the grassland bird community and reproductive performance in CP33 habitat buffers may be influenced by the landscape context (e.g., edge habitat, surrounding land cover). My objectives for this study were to determine how periodic disturbance and the agricultural landscape mosaic influence the breeding grassland bird community in buffers, and how these same factors influence grassland bird nesting success and density in buffers. Data collected during line-transect surveys conducted in CP33 habitat buffers in northeast Mississippi during the 2007-2009 breeding seasons demonstrate periodic disturbance through prescribed burning and light strip-disking does not influence breeding bird diversity or density in buffers. Buffers with woodland at the non-crop edge, however, had the least grassland bird diversity. Dickcissels, one of the most abundant grassland bird species detected in buffers, had a lesser, though non-significant, density in woodland-bordered than in grassland-bordered buffers. I estimated nest success of Dickcissels and Red-winged Blackbirds using maximum likelihood approaches modeling daily survival rates of nests in Program MARK. Analysis results indicated periodic disturbance did not inform models of nest success for either species to an extent requiring inclusion in the best approximating model. Both species, however, had greater nest densities in control and burned buffers than in disked buffers, as well as adjacent to grassland and crop edges. Dickcissel nest success was associated negatively to proximity of developed areas and amount of land cover in crop production, and associated positively with nest height. Red-winged Blackbird nest success decreased with increasing distance from a crop edge and decreasing height of surrounding vegetation, but increased with greater amounts of ground cover. Results from this study will assist land managers with selecting land for enrollment in CP33 that will maximize producers’ conservation goals while minimally impacting crop production, as well as assist with development and refinement of USDA-NRCS Practice Standards, documentation of ecological benefits of federally subsidized conservation practices, and enhancement of wildlife benefits in agriculture-dominated landscapes.