Nitrogen (N) fertilization due to atmospheric deposition (NDEP ) may explain some of the net carbon (C) sink (0.6-0.7 Pg y-1) in temperate forests, but estimates of the additional C uptake due to atmospheric N additions (∆C/∆N) can vary by over an order of magnitude (5 to 200 ∆C/∆N). High estimates from several recent studies [e.g. Magnani (2007), Nature 447 848-850], deriving ∆C/∆N from regional correlations between NDEP and measures of C uptake (such as eddy covariance -derived net ecosystem production, or forest inventory data) contradict estimates from other studies, particularly those involving 15N tracer applications added as fertilizer to the forest floor. A strong ∆C/∆N effect requires nitrogen to be efficiently acquired by trees and allocated to high C:N, long-lived woody tissues, but these isotope experiments typically report relatively little (~ 20 %) of 15N added is found above-ground, with less than 5 % of the total 15N applied found in wood. Consequently the high correlation-derived ∆C/∆N estimates are often attributed to co-variation with other factors across the range of sites investigated. However, 15N-fertilization treatments often impose considerably higher total N loads than ambient NDEP , while almost all exclusively only apply mineral 15N treatments to the soil, often in a limited number of treatment events over relatively short periods of time. Excessive N deposition loads can induce negative physiological effects and limit the resulting ∆C/∆N observed, and applying treatments to the soil ignores canopy nitrogen uptake, which has been demonstrated in numerous studies. As canopies can directly take up nitrogen, the chronic, (relatively) low levels of ambient NDEP inputs from pollution may be acquired without some of the effects of heavy N loads, with trees obtaining this N before it reaches the soil, allowing canopies to substitute for, or supplement, edaphic N nutrition. The strength of this effect depends on how much N uptake can occur across the canopy under field conditions, and if this extra N supplies growth in woody tissues such as the stem, as well as the canopy. Similarly, such mineral fertilizer isotope trace experiments are also unable to trace N in the decomposing litter and humus layers of the soil, which even under heavy NDEP loading contribute most of the N utilised for forest growth. Recent literature suggests that some organic (early decomposition) forms of N may be taken up by roots. If this litter N is not retained or distributed in the same way as mineral fertilizers, its contribution to plant nutrition and ∆C/∆N may need to be reassessed under nitrogen deposition. We tested some of these assumptions in the nursery and the field. In order to facilitate litter 15N tracing, we conducted an experiment injecting large trees with 15N-NH4NO3 to create 15N-labelled litter, tracing the applied isotope into a full harvest of the canopy. Such labelled litter substitute was used to replace the litter layer in a Sitka Spruce plantation (Picea sitchensis L. (Bong.)), where the fate of this 15N from litter decomposition in the soil system was compared against the fate of 15N in deposition. Similarly, in potted Sitka Spruce saplings, we used combination treatments of 15N-labelled litter, soil-targeted 15N-deposition, and canopy targeted 15N-deposition, investigating 15N return in different age classes of above and below ground biomass. We found that i) 15N recovery in canopies (needles and branches) in our injected trees was almost all of the injected 15N five months after injection, ii) canopy application of NDEP led to 60 % 15N return in above-ground parts of saplings compared to 21 % in soil applications and iii) a litter-derived 15N source was retained 55 % more in topsoil, and 36 % more in roots, than a similar deposition 15N source applied as mineral fertilizer. We discuss the implications of such findings in the context of 15N return in different plant organs and ecosystem pools, seasonal variation in N content, and overall inferences of a forest ∆C/∆N effect. Our results suggest that the total ∆C/∆N effect driven by a high N sequestration from canopy uptake in wood is ~ 114:1, more than double that of 15N tracer experiments but not as high as upper estimates from correlative studies, and that litter-derived organic N is better retained in trees and soils in excess of similar amounts of mineral 15N from deposition. Existing forest 15N-fertilization experiments could under-estimate the overall ∆C/∆N effect of atmospheric N deposition.

Graduation date: 1991

The main project Dry preservation of source-separated organic household wastes involves a new technique for treatment of biowaste through drying. Investigations are going on to determine how the dried biowaste best can be used to close the natural circular flow of nutrients. The objective of this degree project is to determine if the dried biowaste can be used as a soil conditioner. By restoring the nutrients in the material to the ground, the natural circular flow is closed. A declaration of contents, including the nutrient levels, C/N ratio, pH and the electrical conductivity of the dried biowaste, was constructed and a germination test was done to make sure that the material did not inhibit sprouting. Further on a method was developed to study the decomposition process, and in particular the nitrogen mineralization of the dried biowaste. This method was then used practically. The results of this degree project indicate that the decomposition capacity of the dried biowaste is very good. The germination test showed that the material in a diluted form (up to 50 % dried biowaste) did not inhibit sprouting. The examination of the nitrogen mineralization showed a fast liberalisation of nutrients available to plants, with only a shorter period of nitrogen immobilization. Together these results imply that the dried material could function well as a soil conditioner. / Projektet Torrkonservering av matavfall från hushåll innefattar en helt ny teknik för behandling av bioavfall genom torkning. Undersökningar pågår angående hur det torkade bioavfallet bäst kan användas för att sluta det naturliga kretsloppet. Examensarbetets huvudsyfte var, som ett led i dessa undersökningar, att utreda om det torkade bioavfallet kan användas som ett jordförbättringsmedel. Genom att tillföra bioavfallet till jord så återförs näringen i materialet till marken och kretsloppet sluts. En varudeklaration, med materialets näringshalter, C/N-kvot, pH och elektrisk konduktivitet, togs fram och ett groningstest utfördes för att kontrollera att bioavfallet inte var groningshämmande. Vidare utvecklades en metod för att studera det torkade bioavfallets nedbrytningsegenskaper i form av dess kvävemineralisering. Denna metod användes därefter praktiskt. Resultatet av detta examensarbete tyder på att torkat bioavfall har mycket goda nedbrytningsegenskaper. Groningsförsöket visade att materialet i utspädd form (upp till 50 % torkat bioavfall) inte är groningshämmande, och mineraliseringsförsöket visade på en snabb frigörelse av växttillgängligt kväve, och en immobiliseringsperiod på ett par veckor. Tillsammans indikerar dessa resultat att det torkade materialet kan fungera väl som ett jordförbättringsmedel.

Nitrogen fixation is no longer considered to be a minor factor of the nitrogen cycle in oceanic ecosystems. Recent geochemical and biological efforts have led to a significant increase in the estimated input of nitrogen to marine ecosystems by biological fixation, while molecular studies have increased our knowledge of the number and diversity of nitrogen fixers known to be active in the ocean. Although Trichodesmium spp. have long been viewed as the primary marine nitrogen fixers, recent efforts have shown that various members of the picoplankton community are also actively involved in nitrogen fixation. The relative abundance of different nitrogen fixers is an important ecosystem parameter since nitrogen fixers may differ significantly in their physiology, life history and ecology. Here we combine rate measurements and stable isotope natural abundance measurements to constrain the impact of N2 fixation in the waters north of Australia. Samples were collected in the Coral, Arafura, and East Timor Seas, thus spanning three distinct hydrographic regions. Our data show that Trichodesmium has a significant influence on the stable nitrogen isotope ratios of particulate and zooplankton biomass and suggest that Trichodesmium is a significant source of nitrogen for the pelagic ecosystem. Based on stable carbon isotope ratios, it is also likely that the pathways are indirect and nitrogen fixed by Trichodesmium enters the higher trophic levels via decomposition as dissolved organic and inorganic nitrogen. Picocyanobacteria showed high diazotrophic activity at some stations, but unlike Trichodesmium, their N2 fixation rate was not reflected in the stable N isotope ratios of particulate and zooplankton biomass. Our results suggest an important N contribution to biomass by diazotrophs in the Coral Sea, Arafura Sea and East Timor Sea.

No description available.

Thesis (Ph.D.)--McMaster University, 2006. / Supervisor: Michael Jerrett. Includes bibliographical references.

Thesis (Ph.D.)--McMaster University (Canada), 2006. / Includes bibliographical references.

AN ABSTRACT OF THESIS Jarrod Armstrong, for the Master of Science degree in Forestry, presented on December 10, 2014, at Southern Illinois University Carbondale. Title: Nitrogen Availability and Transport Following Drought in Three Agricultural Watersheds in Central Illinois Major Professor: Dr. Karl Williard The use of inorganic nitrogen (N) fertilizers has become an essential part of modern agriculture and has helped increase yields to keep pace with an ever growing population. N is the most dynamic nutrient in nature, and biological activity can transform it into several mobile forms. Nitrate (NO3-N) is the most mobile form of N and is highly susceptible to transport to ground and surface waters. The purpose of this study was to assess N dynamics in three agricultural watersheds during and following a significant drought in 2012. Specifically, the study focuses on the mobilization and transport of residual N. The research was conducted on a ninety‐seven hectare agriculture field in Macon, County Illinois. The study site (BRKA) was divided into three watersheds, with four plots per watershed, and two topographic positions per plot. Volumetric water content (VWC) was measured continuously in each of the two topographic positions. In each watershed, stream stage collected over storm hydrographs using automated water samplers was compared to volumetric water content and NO3-N concentrations over the hydrograph. Four 6.1m groundwater monitoring wells and eight vacuum lysimeters in each watershed were monitored to determine the fate and transport of N to soil water and groundwater. Soil sampling at the 15cm depth was completed on a 0.4 hectare grid over the entire field during the fall of each year of the study. Soil and groundwater samples were analyzed monthly to compare NO3-N concentrations across topographic positions. NO3-N concentrations were highest in soil water, followed by groundwater, and lastly surface runoff. Studies in Illinois and Iowa both confirmed large amounts of residual N in the soil after the growing season in the fall of 2012 (Sawyer 2013, and Nafziger 2013). Residual N was apparent at BRKA in elevated NO3-N concentrations in soil water and groundwater after the 2012 growing season. Runoff events in April 2013 also showed increased NO3-N transport. However, due to precipitation events in the late fall and winter the residual N was flushed from the soil profile rendering it unavailable for the 2013 growing season. The soil NO3-N deficit after the 2012 drought was likely the result of decreased N fixation, N mineralization, nitrification, and leaching of any residual NO3-N. Bottomland positions consistently displayed higher soil water and groundwater NO3-N concentrations compared to uplands. However, due to a lack of plant uptake during the 2012 drought this trend was reversed and caused upland positions to exhibit higher NO3-N concentrations compared to bottomlands. This study demonstrated that even during a soybean year when no N fertilizer was applied significant drought can effectively alter the normal N dynamics at the field scale. Furthermore, this change in dynamics can lead to elevated NO3-N concentrations in soil water and ground water. These findings also suggest that precipitation events following periods of drought, like those observed after the 2012 growing season, can flush excess nutrients from the rooting zone further depleting the NO3-N pool and posing a risk to water quality. Data from a June 15, 2011 storm showed that on the falling limb of the hydrograph subsurface flow flushed soil water from the top of the slope to the bottom of the slope. This is indicative of a variable source area controlled watershed where the near stream zones undergo prolonged saturation from the subsurface drainage of the upland areas. Additionally, the early peak of NO3-N during an April 18, 2013 surface runoff event could be attributed to increased mineralization and nitrification following a rewetting of the soil profile after the 2012 drought. Lastly, topography was shown to have a strong influence on soil NO3-N concentrations across the field. This finding suggests that fertilizer applications based on topography and hydrology could help to mitigate the loss of excess NO3-N from agricultural watersheds. Furthermore, fertilizer applications should be adjusted for drought conditions that extend into the following growing season to account for residual N in the soil.

Nitrogen (N) is known to be a limiting factor in peatlands and as such, the vegetation present has adapted to living in low N conditions. This makes such ecosystems particularly vulnerable to increases in the deposition of reactive N (Nr), which may result in significant changes to its biodiversity and biogeochemistry. Since the industrial revolution, the amount of anthropogenic Nr globally has increased from ~15 Tg N y-1 in the 1860’s to ~187 Tg N y-1 in 2005, and is estimated to reach ~267 Tg N yr-1 by 2050 (Galloway et al. 2004, Galloway et al. 2008). Consequences include acidification, loss of biodiversity, changes in vegetation, N-saturation, eutrophication, health impacts and the release of greenhouse gases.Objectives of this thesis were (i) to measure key components of the N-budget at Auchencorth Moss, a Scottish moorland, for a two year period (Jan 2009 – Dec 2010) and (ii) to compare current deposition rates with those measured 14/15 years previously. Annual fluxes of N inputs were estimated from measurements of wet only deposition, estimates of N-fixation deposition and from atmospheric deposition modelled from hourly concentrations of N containing gases and aerosols. Exports were estimated from stream measurements and from atmospheric emissions modelled from hourly concentrations. Organic N is often an underreported part of the N-cycle, but the results presented here suggest it is an important part of the N story. An attempt to identify (dissolved organic nitrogen) DON compounds in both precipitation and stream water was made using GC×GC-NCD. Ten unique compounds were detected, of which only five could be identified: pyrrole, benzonitrile, dodecylamine, N-nitrosodipropylamine and decylamine. Pyrrole, benzonitrile and three unknown compounds were present in both precipitation and stream samples. Ammonia (NH3) fluxes were measured over a 7 month period in 2009 using a wet-chemistry gradient system with online analysis and calculated with the aerodynamic gradient method. The results were used to refine a bi-directional dynamic exchange model. Several parameters were updated, including an increased stomatal emission potential from 180 to 350, a reduction of the minimum cuticular resistance (Rw,min) used to calculate Rw from 20 s m-1 to 15 s m-1 and an increase in the leaching rate (Kr¬) from the leaf surfaces from -0.01 to -0.1 s-1. The exchange parameterisations used to estimate HNO3, HONO and the aerosol compounds were taken from the literature and earlier studies at the site.Overall, Auchencorth was found to accumulate N, with deposition exceeding export by -1.61 kg N ha-1 yr-1. The main N deposition was from NH3, followed by wet deposition of ammonium. DON, which is not routinely included in N budgets, contributed 6.5% of total deposition. The largest loss of N was as DON via the stream with N losses of -5.31 kg N ha-1 yr-1 or 71.8% of total export. Between 1995 and 2009/2010, deposition decreased by 0.81 kg N ha-1 yr-1, with the wet deposition of inorganic nitrogen decreasing by 25.2%, but dry deposition increasing by 12.5%. DON, N2O and N-fixation were not included in the comparison as they were not measured in 1995.This thesis has demonstrated that DON is an important parameter in the overall N budget, and should be routinely measured when assessing the N status of ecosystems.

Use of switchgrass (Panicum virgatum L.) as a forage and feedstock species requires knowledge of fertilizer application rates and harvest timing to optimize yield and quality. Three experiments were conducted at the Brown Loam Branch Experiment Station, Raymond, MS to quantify nitrogen rates, harvest timing, and genotype effects on biomass, nutrient removal, chemical composition and ethanol yield. Dry matter yield varied with N rate, genotype, harvest frequency and timing. Yields among genotypes were: NF/GA992 = NF/GA001 (13.7 Mg ha-1) > Alamo (11.6 Mg ha-1) > Cave-in-Rock (6.1 Mg ha-1). A single (9.5 Mg ha-1) or two harvests annually (10.3 Mg ha-1) produced the greatest dry matter yield. As harvest frequency increased from three (7.3Mg ha-1) to six (5.9 Mg ha-1) harvests annually, yield decreased. There was an effect of N application on yield, but not at application rates greater than 80 kg ha-1. Nitrogen did not consistently affect tissue nutrient concentrations but more frequent harvests led to increased nutrient concentration. Nutrient removal responses to N application were mostly similar to the yield responses. Nitrogen use efficiency and recovery declined as N rate increased. Estimated ethanol yield averaged 162 L Mg-1 for Alamo, NF/GA001 and NF/GA992 . A single (2.4 kL ha-1) or 2 harvests annually (2.3 kL ha-1) produced the greatest ethanol production and was correlated with by biomass yield. Nutrient removal, N use efficiency, N recovery and ethanol production were related to biomass yields rather than chemical composition differences. The findings in this dissertation will enable a database on management effects on ethanol yield and composition, enhance current biomass models, facilitate improved management of feedstock production inputs and improve feasibility of alternative fuel development.