NRSM Masters Theses (Plan A and Plan B)
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Item Soil moisture and soil frost regimes under annual, perennial and agroforestry Crops in Waseca, Minnesota.(2010-03) Byrne, Marin Johanna.The potential for agroforestry and other perennial crops to provide hydrologic benefits is of interest in the Minnesota River Basin, where the landscape is dominated by annual row crops and the river is plagued by water quality and quantity issues. Perennial herbaceous and woody crops are thought to have higher annual consumptive use of water than annual corn-soybean crops, influencing antecedent water status, creating more water storage, potentially decreasing discharge, and reducing the duration of soil frost and prevalence of concrete soil frost in the early spring. Quantification of potential hydrologic benefits is needed to provide support for more sustainable agroforestry and other alternative cropping practices in the basin. To this end, in the summers of 2004 and 2005, biweekly measurements of soil moisture under one annual crop (corn/soybean rotation), two perennial herbaceous crops (perennial flax and Illinois bundleflower) and two woody crops (hybrid hazelnuts and hybrid willow) were taken on replicated experimental plots at the University of Minnesota’s Southern Research and Outreach Center in Waseca, Minnesota. Similar measurements were taken in a stand of mature hybrid poplar and a field planted in a corn/soybean rotation. Likewise, soil frost depth, duration, and type were measured under the same crop types during the intervening winter. Analysis of soil moisture data showed few significant differences in soil moisture between the various crop types on the experimental plots, perhaps due to a combination of the perennial and agroforestry crops being in the establishment phase and unusually wet weather. The mature poplar stand had consistently drier soils than the cornfield during the 2004 season, although these differences disappeared during the course of the 2005 season, likely due to a change in management of understory plant cover in the poplar stand. During the winter, no significant differences in soil frost duration or type were observed, likely due to uniformly wet fall soil conditions, a lack of snow during the coldest part of the winter and rapid spring warm up. Thus, agroforestry and herbaceous perennial crops appear to provide little hydrologic benefit during the establishment phase or in winters with low snowfall, but when mature or in winters with heavier snowfall, could have the potential to provide such benefits.Item Post-stratified estimation of Coarse Woody debris Volume using the down woody materials sample of forest inventory and analysis.(2010-05) Hatfield, Mark A.The Forest Inventory and Analysis (FIA) program of the USDA Forest Service conducts a nation wide survey of America’s forests. FIA field crews collect data on tree size, condition, and species, as well as data on the conditions in which they grow from a network of permanent ground plots known as Phase two plots (P2). FIA crews also collect more detailed forest health indicators, including data on Coarse Woody Materials (CWD), on a 1 16 subset of the P2 sample. This subset is known as the Phase 3 (P3) sample. FIA regularly publishes reports on the quantity and quality of America’s forests using data from the P2 sample. A post-stratified estimation technique is used increase the precision of the estimates without increasing the sample size. Currently, research on how to best apply the post-stratified estimator to produce estimates of the P3 forest health indicators has been lacking. This thesis will address this gap by testing 18 candidate geospatial layers (both categorical and continuous) as stratification layers to produce estimates of CWD volume in the Lake-states region of Minnesota, Wisconsin, and Michigan. Continuous geospatial layers will be broken into two to five strata using an optimization algorithm. A simulation experiment is used estimate the long term effectiveness of successful geospatial layers. The simulation experiment is performed to compare the conditional and unconditional variance estimators of the post-stratified estimators. Successful geospatial layers are then applied to sub-populations of varying sizes to determine the effect of spatial extent on the post-stratification method. Stratification layers derived from remote sensing products provided the best results. Using two or three strata is recommended because further partition of the population simply produces ineffective sliver strata. No difference was detected between the two competing variance estimators. The effect of spatial extent of the stratification was volatile. The use of large spatial extents is recommended. The conclusion of this thesis summarizes the lessons learned throughout as well as ideas for future research on the topic.Item The role of predator removal and density-dependence on mallard production in northeastern North Dakota(2010-05) Amundson, Courtney LindaDensity-dependence is a central tenet of wildlife population dynamics and harvest management, yet the pathways and mechanisms by which density-dependence operates remain unclear. In 1994, Delta Waterfowl Foundation began trapping meso-predators in northeastern North Dakota to determine if it was a viable technique for increasing waterfowl production. Subsequent research on replicated experimental sites found that trapping predators increased nest success by about 2-fold, and nest success was the most important factor regulating population growth in previous studies of midcontinent mallards. Given the philopatric nature of most waterfowl species, higher nest success on trapped sites was predicted to lead to 36% greater annual population growth on trapped sites versus controls, which should have led to doubling of pair densities approximately every two years. This backdrop provided me with the unique opportunity to examine the role of density-dependence on waterfowl production at a local scale in North Dakota. My dissertation focuses on the role of density-dependence and predator removal on mallard duckling survival, duckling body condition, and overall mallard productivity in northeastern North Dakota from 2006-2007. Contrary to predictions, predator removal had no beneficial effect on mallard duckling survival. Duckling density was weakly negatively associated with mallard duckling survival, but had no effect on duckling condition. Duckling survival, not nest success, was the most important factor influencing population growth and production and appeared to be functioning as the key limiting factor in our populations. Overall, predator removal did not lead to local population increases on trapped sites and added far fewer incremental ducks to the fall flight than originally predicted. The perils of duck hunting are great - especially for the duck. - Walter Cronkite.Item Effects of site and climate characteristics on forest invasibility by non-native plants in the Midwest.(2010-07) Kurtz, Cassandra MarieNon-native invasive plant (NNIP) species can have significant effects on forest regeneration, structure, biodiversity, and wildlife habitat, costing billions of dollars annually. Understanding how NNIPs in the Midwest may spread in the future requires understanding their response to site and climate characteristics. Current research suggests climate change may influence invasive plant presence and spread. In this study, I modeled the relationship between invasive species presence, site characteristics (e.g. disturbance, live tree volume, city distance, edge distance, physiography, and type of water [e.g. streams] present on plot), and climate (annual average number of days the temperature is ≥ 90˚F and annual average number of days the temperature is ≤ 32˚F) for five non-native invasive plants (multiflora rose [Rosa multiflora], common buckthorn [Rhamnus cathartica], non-native bush honeysuckles [Lonicera spp.], garlic mustard [Alliaria petiolata], and reed canary grass [Phalaris arundinacea]) sampled by the USDA Forest Service’s Forest Inventory and Analysis program in seven Midwestern states for 2005-2006 Species’ response to site and temperature predictors varied due to trait differences such as shade tolerance and moisture affinity. For most species, presence was positively related to biotic disturbance (disease(s) and/or animal(s)) and mesic physiography and negatively related to distance from a city or a nonforest edge. The best predictor for the presence of NNIPs was annual average number of days the temperature is ≤ 32˚F, with all five species presence correlated with the annual average number of days the temperature is ≤ 32˚F. Understanding the effect of site characteristics and climate on NNIP distribution provides insights into important drivers of species presence at a regional scale and allows land managers, scientists, and concerned citizens to predict invasion risk and future ecosystem response.Item The influence of stand stocking level on the growth and structure of managed old-growth northern hardwoods.(2010-09) Gronewold, Christopher AlanSummary abstract not available.Item American Woodcock Singing-ground Surveys in the western Great Lakes region: assessment of woodcock counts, forest cover types along survey routes, and landscape cover type composition.(2010-10) Nelson, Matthew RoyOverview: Counts of American woodcock (Scolopax minor) on the annual Singing-ground Survey (SGS) have undergone long-term declines in both the Eastern and Central Management Regions. However, interpreting these trends is confounded by a lack of information regarding the relationship between counts and habitat. Therefore, I assessed the relationship between woodcock counts and land-cover composition along survey routes using an Information-Theoretic modeling framework. The amount of early successional forest, open space, and a landscape metric Interspersion and Juxtaposition Index (IJI) best explained counts in Wisconsin; in Minnesota, the amount of mature forest, water and models that included open space, wetlands, and early successional forest together best explained counts. These results are, in general, consistent with woodcock-habitat relations described in published literature, and suggest that woodcock counts along SGS survey routes in Minnesota and Wisconsin reflect the amount and composition of land cover along routes, especially the amount and juxtaposition of early successional forest and open space, which were the variables included in competing models for both states. Key Words: shorebird, American Woodcock, Scolopax minor, Central Management Region, Minnesota, Wisconsin, land cover.Item Riparian plant composition, abundance, and structure responses to different harvesting approaches in riparian management zones nine years after treatment in Northern Minnesota, U.S.A.(2010-11) Martin, Michelle AmberI compared riparian plant responses to different harvesting approaches over nine years in Riparian Management Zones (RMZ) in Northern Minnesota. In Chapter 1, I found that tree regeneration in RMZs is greater in partially harvested treatments (60% BA removal) than in unharvested treatments. This was especially true of intolerant tree species, although the shade tolerant species are becoming important in lower strata at year nine post-treatment. In Chapter 2, I found that understory plant community composition and abundance change somewhat over time in partially harvested treatments in comparison to unharvested treatments. This was especially true of woody understory layers, however, less so for the herbaceous layer. In general, the understory plant community shifted toward more shade intolerant and disturbance indicating species. As of nine years post-treatment, partially harvested RMZs balance timber and non-timber management objectives as they increase tree regeneration and do not dramatically alter understory plant communities.Item All cellulose composites prepared in an ionic liquid.(2010-12) Zhou, LiliThe overall goal of this project was to investigate all-cellulose composites prepared in a “green” solvent – ionic liquid. The approach was to partially dissolve cellulose and subsequently convert it into a matrix domain embedding the reinforcement domain – the undissolved cellulose. Microcrystalline cellulose (MCC) was partially dissolved in 1-N-Butyl-3-methylimidazolium chloride (BMIMCl) ionic liquid. The dissolved portion of cellulose was precipitated by adding water, and the gels obtained were washed, dried, and pressed into films. The all-cellulose composite films were structurally characterized using x-ray diffraction (XRD) and scanning electron microscopy (SEM), while their properties were determined using tensile tests and dynamic vapor sorption (DVS) studies. XRD results verified that the crystallinity index and weight fraction of cellulose I in the composites can be controlled by controlling the soaking time and cellulose concentrations. The tensile test data revealed that the all-cellulose composite produced in this study had mean elastic moduli and strength of up to 4.4 GPa and 49 MPa, respectively, which are in the range of a randomly oriented biofiber-reinforced polymer composites. The tensile properties increased as a response to the composite density, which was found to increase as more cellulose II matrix (from increased dissolution) was present to presumably better fill the voids. This presumption was supported by SEM images of cryo-fractured surfaces. The sorption isotherms obtained from DVS studies showed a non-sigmoidal behavior at low relative humidity levels (<44%), while the equilibrium moisture content values at higher humidity levels closely correlated to the cellulose I crystallinity index of the composites. Overall, this study verified that dissolution of cellulose in ionic liquid can be controlled to control the properties of all-cellulose composites.Item The influence of natural disturbance-based silviculture treatments on northern hardwood forests in Northeastern Minnesota, USA.(2010-12) Bolton, Nicholas WilliamNatural disturbance-based silviculture (NDBS) has been suggested as an approach for promoting late-successional forest characteristics and maintaining native biodiversity in managed forests. Harvest gaps based on the natural disturbance patterns found in the upper Great Lakes (46 study gaps) were created throughout northern hardwood forests in northeastern Minnesota, USA, during the winters of 2002 and 2003. Gaps were measured 6- and 7-years post-treatment and subsequent analysis of these measurements was used to evaluate the success of these treatments at meeting structural and compositional objectives. Results indicated that these gaps have done little to increase tree diversity, including the recruitment of shade mid-tolerant species; however, the richness of herbaceous understory vegetation has responded positively to larger gap sizes. Herbaceous species increasing in harvest gaps included Actaea spp. L. (baneberry), Botrychium virginianum L. (rattlesnake fern), Mertensia paniculata Aiton (Northern bluebell), Rubus idaeus L. (red raspberry), Sanguinaria canadensis L. (bloodroot) and Cirsium arvense L. (Canada thistle). Results also indicated that subtle patterns were found among species spatial establishment within gaps (e.g., gap edge and gap center) and species that expressed no preference between the intact forest and harvest gaps. Levels of downed coarse woody debris (CWD) differed among gap size and all gaps had lower levels of CWD compared to the surrounding intact forest. Due to the historical importance of Betula alleghaniensis in these systems, the factors affecting the recruitment of this species were also investigated. Based on these investigations, it was found that B. alleghaniensis establishment was strongly related to highly decayed, large coniferous pieces of CWD with little recruitment occurring on the undisturbed forest floor. As such, providing appropriate seedbed conditions for shade mid-tolerant species and utilizing natural canopy gap sizes would improve the success of maintaining this species on the landscape.Item Canopy transpiration and water yield changes following forest canopy conversion in Northern Minnesota.(2011-03) Shannon, JosephIn 1980, the upland aspen (Populus tremuloides & P. grandidentata) portion of the S6 watershed of the Marcell Experimental Forest was clearcut and subsequently converted to red pine (Pinus resinosa) and white spruce (Picea glauca). Comparisons of water yield observed at S6 and that predicted using the aspen dominated S2 control watershed, suggest that streamflow from S6 has decreased over the past two decades as the conifers have matured. Granier-style thermal dissipation probes were used to quantify sap flux in 36 trees in S2 and S6 throughout the growing season to determine if transpiration rates differed between the two watersheds. Representative sample trees were selected according to factors which may cause sap-flux rates to differ: tree species, slope position, and slope aspect. Using forest inventory data, sap-flux rates were up-scaled to watershed canopy transpiration. Transpiration losses in the S6 watershed were 30% greater than those in S2 for the duration of the study period. Differences were primarily driven by a longer growing season in conifers and greater forest basal area in S6. By representatively sampling forest species it is possible to show that 40 - 50% of transpiration in each watershed is the result of one dominant species, red pine or aspen, in the experimental or control watersheds respectively. Future use of these data will include combination with concurrent interception and flow routing studies to better evaluate hydrologic impacts of similar management decisions in the future. Forest conversion is an ongoing management strategy that brings about long-term effects on streamflow. Understanding these effects allows better prediction of the effect of management on water resources.Item Disturbance dynamics and carbon storage in southern boreal mesic aspen mixedwood forests of northern Minnesota, USA.(2011-05) Reinikainen, Michael RichardOne emerging objective related to forest management is developing silvicultural systems that increase the levels of carbon storage so as to mitigate or offset atmospheric concentrations of carbon dioxide. Understanding the ecological factors and conditions that led to the development of forest stands with high levels of carbon storage can allow for the formulation of management prescriptions that emulate the frequency, timing, and severity of disturbances leading to these conditions. The aims of this thesis were to (1) generate an understanding of the factors affecting stand-level structural and compositional development in southern boreal mesic aspen mixedwoods (hereafter referred to as ‘aspen mixedwoods’), and (2) identify relationships between carbon storage, stand characteristics (e.g., composition and structure) and disturbance histories. Dendroecological methods were used to detail the mechanisms by which nine aspen mixedwood stands in northern Minnesota developed in terms of composition and structure over the last nine decades. With that knowledge and detailed plot-level measurements of forest carbon pools, relationships between patterns of carbon storage resulting from various disturbance histories and compositional mixtures were examined. Dendroecological reconstructions demonstrated that the development of mature aspen mixedwoods was strongly influenced by the defoliation of trembling aspen (Populus tremuloides) by forest tent caterpillar (FTC: Malacosoma disstria) and of balsam fir (Abies balsamea) by eastern spruce budworm (SBW: Choristoneura fumiferana), resulting in complex multi-aged forests. Notably, disturbance-induced structural and compositional changes began as early as 30 years after stand initiation. Concerning carbon storage, stands with a high proportion of aspen stocking resulted in greater total ecosystem (TEC) and tree carbon (TREEC) storage with an opposite trend observed with proportion of conifer, particularly balsam fir. However, in light of recent disturbance, stands containing a greater diversity of tree species and a greater proportion of conifer stems had higher rates of tree carbon increment over the last two decades than plots with a greater proportion of aspen. Furthermore, lower levels of TEC in plots that had experienced elevated rates of disturbance over the last three decades were documented. Collectively, these findings highlight the influence of low to moderate severity disturbances on the patterns of carbon storage and compositional and structural complexity within these systems. As such, regional patterns of natural disturbance present a challenge within the context of managing for highly productive mature aspen mixedwoods; however, the restoration of historically important species (i.e., Picea glauca, Pinus strobus and Thuja occidentalis), specifically long-lived species resistant to FTC and more importantly SBW, may offer a means to store large amounts of carbon for longer periods.Item Raman spectroscopic studies of load transfer in microfibrillated cellulose/poly(Lactic acid) composites.(2011-07) Yao, JinThe objective of this research was to investigate the feasibility of using Raman-tensile tests to evaluatethe transfer of load between polylactic acid (PLA) and cellulose nanofibers. Microfibrillated cellulose (MFC) was modified with oligomeric lactic acid. The modified MFC was loaded into a PLA solution before being cast into a film. The nanocomposite films were subjected to tensile loading during which Raman spectroscopy was performed under a microscope. The Raman spectrum of MFC was isolated from the spectrum of its composites. The stress-sensitive Raman band of cellulose (1095 cm-1) was analyzed for wavenumber shift, which is an indication of load transfer from the PLA matrix to MFC. Compared to the control (untreated) sample, composites with lactide-treated MFC exhibited a higher Raman band shift as a response to both applied strain and stress, indicating an improved efficiency of load transfer across the compatibilized interphase between nanofibers and PLA. The effect of MFC addition ratio on the load transfer ability was also discussed. A higher MFC weight fraction (0.5 % versus 0.25 %) in the composite did not significantly affect the load transfer efficiency. This finding suggests that the efficiency of matrix/fiber load transfer at the local level is independent of the effects of macroscopic fiber-to-matrix ratio, at least at the (low) levels of MFC loading examined in this study. Overall, this research shows that it is feasible to use Raman spectroscopy to monitor load transfer in MFC/PLA composites for examining strategies aimed at improving adhesion and knowledge of the mechanism of PLA reinforcement by nano-cellulose.Item Factors influencing detection of American woodcock during singing-ground surveys.(2011-07) Bergh, Stefanie M.Abstract summary not availableItem Microscopic and thermal characterization studies of heterogeneous biocatalysis: polyurethane film immobilized enzymes and degradation of algal cells.(2011-07) Song, WeiHeterogeneous biocatalysis, associated with either solid-state biocatalyst systems or solid-state substrate systems, has garnered a lot of interest for chemical synthesis, bioseparation, and biosensing. In the pursuit of high efficiency, the characterization of the physical structure of solid-state biocatalysts and solid-state substrates is necessary to provide detailed information and deepen the understanding for the heterogeneous biocatalytic systems. In this study, microscopic and thermal analytical methods were utilized to characterize the physical structure of solid-state biocatalysts and solid-state substrates. Particularly, we chose the versatile polymer polyurethane (PU) to immobilize enzymes as model solid-state biocatalysts. Two important physical properties, enzyme distribution and glass transition temperature (Tg), were analyzed. It was found that several preparation parameters, including hydrophobic/hydrophilic properties of resin and cross-linker for PU film, weight ratio of starting materials, and mixing speed, showed significant influences on enzyme distribution and Tg. Using microscopic and thermal characterization methods, we further studied the integrity of enzyme-containing PU film against water. The enzyme was found prone to leak from the PU film, indicating incompleteness of cross-linking with PU. Several approaches (e.g., increasing the reaction time and using a hydrophilic cross-linker) were explored in this work to promote better cross-linking between the enzyme and PU matrix. The hydrophilic cross-linker (Bayhydur 302) demonstrated 70% improvement in retaining the enzyme against 24 hours of washing compared to a hydrophobic cross-linker (DESMOPHEN N3600). Moreover, algae cells were studied as model solid-state substrates. We report a novel enzymatic method to disrupt the cell wall and release lipids from the algae cells. Microscopic analysis indicated that the cell wall of Chlamydomonas reinhardtii (C.R.) algae was disrupted after being treated by a three-step method, which included one hour of incubation in 4 M of lithium chloride, eight hours of hydrolytic reaction in enzyme solution, and one cycle of freeze/thaw process. Protease Subtilisin Carlsberg was found effective in catalyzing the degradation of C.R. cell wall due to its unspecific activity toward peptide bonds.Item Selection of landscapes by male ruffed grouse during peak abundance.(2011-08) Kouffeld, Meadow JeanMost research on ruffed grouse (Bonasa umbellus) habitat selection has focused either on habitat structure within their activity centers or characteristics of forest stands containing activity centers. I studied the relationship between landscape configuration and density of male grouse during the high portion of their cycle. I located 290 and 230 male grouse during 2009 and 2010 respectively, on 30 landscapes encompassing 5,349 hectares. I used information theoretic model selection to examine two sets of a priori models. The top model in the first set was the null model (intercepts only), but a model representing Shannon‘s Evenness Index was competing. This competing model contained the second greatest cumulative weight (AICcwi = 0.203). Shannon‘s Evenness Index was positively correlated with male grouse density (R= 0.43). The effect of Shannon‘s Evenness Index within landscapes was difficult to interpret because it was confounded by cover type dominance in landscapes. The proportion of the aspen cover type was positively correlated (R= 0.55), and the proportion of the conifer cover type was negatively correlated (R= -0.79) with Shannon‘s Evenness Index. The top ranked model in my second set of models was based on road density and had the greatest cumulative weight (AICcwi= 0.52). Road density was negatively related to grouse density (R= -0.34), which could mean either that hunting pressure affects density or habitats were different in landscapes with higher road densities. The year only model indicated that male grouse density declined from 2009 to 2010 (βYear= -0.014, 95% CI = -0.024 to -0.005).Item Response of Thuja occidentalis and Abies balsamea seedlings to stand manipulations in Northern Minnesota riparian forests.(2011-11) Haworth, Brooke KarenNorthern white-cedar (Thuja occidentalis L.), a long-lived conifer closely associated with many riparian boreal forests of Minnesota, is an important species to riparian ecosystem health and to the forest products industry. Northern white-cedar is currently experiencing a decline in recruitment throughout much of its natural range, due primarily to herbivory by white-tailed deer (Odocoileus virginianus). Herbivory on northern white-cedar removes seedling and sapling size classes, and allows less browsed species (notably balsam fir (Abies balsamea (L.) Mill) to further displace the northern white-cedar forest component. This study examined practices that could encourage advance regeneration of northern white-cedar in the riparian setting. The role of partial overstory removal and forest floor microsite was tested on the development of planted 3-0 seedlings of northern white-cedar and the potentially competitive species of balsam fir. Seedlings were planted in mound, pit, and slash microsites (important to seedling germination and establishment) in partially harvested and unharvested riparian areas, and assessed for survival and growth over a four-year period. The test was duplicated inside and outside of fenced plots to evaluate the impact of deer browse and to more fully understand the current dynamic between species. Protected from herbivory, results indicated that partial harvest of the overstory contributed to significant seedling growth with both species demonstrating potential to recruit into taller height and larger basal diameter classes. Basal diameter growth rates were greater in northern white-cedar than balsam fir. Microsites of mound, pit, and slash did not contribute significantly to growth. Percent survival of northern white-cedar was greater than balsam fir, which experienced lower survival in controls. Due to seasonal flooding, pits had a significant negative effect on survival of both species. When protected from herbivory, planted northern white-cedar seedlings were shown to be good candidates for outplanting in a variety of riparian settings, particularly partial harvest areas, and were competitive with balsam fir seedlings for up to four years in the field. Percent browse frequency on unfenced seedlings was greater in harvest treatments and on mound microsites. Unfenced northern white-cedar seedlings were browsed at a significantly higher rate than balsam fir. Northern white-cedar showed significant mortality and no height increase in any treatments, with browse on seedlings overwhelming the benefits of overstory harvests. However, seedlings continued carbon allocation to basal diameter. In addition, northern white-cedar displayed survival resiliency, although reduced vitality, for the four years subjected to herbivory. Basal diameter increase and survival of browsed northern white-cedar seedlings are most likely due to their ability to replace browsed foliage in the current year. Unfenced balsam fir seedlings maintained growth responses to harvest treatments and did not experience significant mortality due to browse. Balsam fir seedlings exhibited the potential to recruit successfully into the overstory even under browse pressure, while northern white-cedar did not. Management activities that increase light availability while retaining some overstory structure, and selection of planting sites that limit or exclude browse, will result in the best chance for northern white-cedar seedlings to recruit into the sapling stage.Item U.S. agricultural phosphorus partial nutrient balances and temporal nutrient use trends within Minnesota.(2011-12) Yee, Scott W.The intensity of phosphorus use in United States food production systems has raised concerns about the use-efficiency of this non-renewable resource. Past research modeling the material flows of phosphorus has found that approximately one quarter of all phosphorus losses occur within the crop cultivation phase of phosphorus’s life cycle. Imbalanced phosphorus inputs and output can result in accumulations of phosphorus within the soil environment and possible phosphorus flows out of cropland. Improvements in phosphorus management are important because excess phosphorus input into the environment can drive hypoxia and cause eutrophication in freshwater, marine, and estuary aquatic ecosystems. The research being conducted in this study builds upon previous material flow analysis (MFA) research and quantifies the partial nutrient balance of phosphorus. Research conducted in this study uses nutrient use efficiency metrics to quantify the ratio of nutrient applied and crop biomass removal. Calculations of phosphorus partial nutrient balances measure system nutrient use sustainability, specifically by calculating the ratio of biomass removal to nutrient input application. Partial nutrient balances were calculated for 1997 within 48 states and within 84 Minnesota counties in 1987, 1992, and 1997. Research conducted in this study has found that phosphorus inputs at the state and county level exceed annual crop harvest, except for a few instances when nutrient removal exceeds inputs. The temporal analysis of partial nutrient balance change has determined that the balance of phosphorus removal and input has improved from 1987 to 1997. These results show that soil fertility, crop uptake, and nutrient application vary and agricultural land management may be improved to better balance crop removal with nutrient inputs.Item Impacts of biomass harvesting on biomass, carbon, and nutrient stocks in populus tremuloides forests of Northern Minnesota, U.S.A.(2012-02) Klockow, Paul AlanGlobally, there is widespread interest in using forest-derived biomass as a source of bioenergy. While conventional timber harvesting generally removes only merchantable tree boles, harvesting biomass feedstock can remove all forms of biomass (i.e., trees down through to forest floor material) resulting in a greater loss of biomass, nutrients, and habitat from a site. To investigate the potential impacts of this practice, this study examined the initial impacts (pre- and post-harvest) of various levels of slash and live-tree retention on biomass and nutrient stocks in Populus tremuloides-dominated forests of northern Minnesota. Treatments examined included 0%, 20%, and 100% slash retention with no, dispersed, and aggregate live-tree retention. Slash retention was the primary factor affecting immediate post-harvest biomass and nutrient stocks within total ecosystem and woody debris pools. High levels of biomass and nutrients in harvest slash were observed in all treatments compared to the unharvested control. Typically, 100% slash retained treatments contained significantly greater biomass and nutrient stocks than no slash retained treatments. Stocks of biomass and nutrients within the 20% slash retained treatment, a slash retention level currently recommended by Minnesota’s biomass harvesting guidelines, were generally similar to both no slash retained and 100% slash retained treatments. Given the importance of fine woody debris as a source of nutrients following harvest, nutrient concentrations were measured across an array of woody debris size and decay classes within the Populus tremuloides-dominated forests examined. Results indicate that fine woody debris has significantly greater nutrient concentrations than coarse woody debris. In addition, nutrient concentrations generally increased within both coarse and fine woody debris as decay progressed. Collectively, the results of this study underscore the importance of deliberate retention of fine woody debris as a source of nutrients following harvests of biomass feedstocks.Item Nest-site selection and nesting ecology of red-headed woodpeckers.(2012-05) Waldstein, Ariane LentzRed-headed woodpeckers (Melanerpes erythrocephalus) were once a common and widespread species in the Midwest but have declined sharply in the last 40 years. This species is a Minnesota Species of Greatest Conservation Need and an oak-savanna specialist; its decline is ascribed to severe habitat loss throughout the Upper Midwest. Despite numerous oak savanna restoration efforts throughout Minnesota, populations continue to decline, and most restoration sites have failed to attract red-headed woodpeckers. Most restoration focuses on prescribed fire but few studies have examined red-headed woodpecker habitat use and nest success in a long-term managed landscape. This thesis explores red-headed woodpecker nest-site selection and distribution at Cedar Creek Ecosystem Science Reserve (Chapter 1) and also describes a cavity camera system to measure woodpecker nest success (Chapter 2). Using data collected at 102 nest sites and 104 random, non-used sites, logistic regression models showed that woodpeckers preferred low densities of small snags and high densities of trees with dead limbs < 10 m above ground level. Models also showed a preference for large dead nest trees. These results are consistent with other studies and are likely a function of this species’ diverse foraging ecology. Examination of the distribution of nests revealed that the highest density occurred in areas burned between 20 - 25 times since 1964. Implementation of a high-frequency burn regime may be effective at creating red-headed woodpecker habitat. The cavity camera system utilized in 2011 was cheaper and easier to assemble than published designs (Chapter 2). One season of use revealed an average of 3 nestlings and two instances of nest depredation.Item Hydrologic, nutrient, and sediment responses of restored perennial vegetation/wetland complexes in southern Minnesota.(2012-05) Fransen, Greg DavidThe Blue Earth River basin, located in the prairie pothole region of northern Iowa and southern Minnesota, is intensively ditched and drained to improve agricultural production. Agricultural drainage systems increase watershed drainage density and can efficiently transport easily leachable agricultural contaminants, such as nitrate, to receiving water bodies. This thesis examines the hydrologic and water quality benefits provided by two restored perennial vegetation-wetland complexes in the Elm Creek subwatershed of the Blue Earth River basin. Flow measurements and water quality samples were collected at the wetland outlets and at drain tiles and surface channels flowing into the wetlands. Four years of flow data showed that the wetlands reduced the magnitude of peak flows to Elm Creek, but that they did not significantly reduce water yield compared to the agricultural watersheds. The restored wetlands decreased nitrate export by 85 percent during the months of April to June, the period when nitrate from agricultural drainage water contributes to formation of the “dead zone” in the Gulf of Mexico. The wetlands did not significantly decrease phosphorus or sediment export to Elm Creek. Water quality benefits attained by trapping phosphorus and sediment from surface runoff were offset by internal phosphorus loading, algal blooms, and sediment resuspension. Empirical modeling of one wetland basin showed that wind speed and wind direction could explain 60 percent of the suspended sediment concentration within the wetland. Active management of water levels and wetland vegetation are presented as strategies to reduce sediment and phosphorus export from restored wetland basins.