Tesi: "Biogeochemical effects"

1

Miller, Bradley W. "Long-term Effects of Fertilization on Phosphorus Biogeochemical Pools in Forest Soils". Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/37386.

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Southern pines are typically limited by nitrogen (N) and phosphorus (P) availability in the soil environment. While the absolute quantities of P in forests soils may be large, the concentration of inorganic P in the soil solution is typically very small (&60; 0.01 mg L&178;-1). A onetime application of just 56 kg P ha&178;-1 can substantially increase growth of pine stands over a 20 year rotation (Pritchett and Comerford, 1982&59; Allen et al., 1990). Phosphorus fertilization of Pinus radiata in New Zealand has also shown long-term effects on labile P pools in the soil which improved stand growth during the subsequent rotations (Ballard, 1978&59; Gentle et al., 1986). Identifying and quantifying the biologically available P pools in the soil environment will help foresters in making site-specific P fertilizer prescriptions. I examined soil phosphorus pools using the Hedley sequential fractionation procedure and Mehlich-3 soil tests in a long-term loblolly pine (Pinus taeda L.) fertilization trial from four sites in the Atlantic and Gulf Coastal Plains. After 22 years, fertilization effects were limited to the surface depths. Mehlich-3 extractable P was largest in the soil surface (0-10 cm) of the fertilized treatments plots. Hedley labile and moderately labile P pools were also largest in the soil surface and decreased with depth. Results from the Hedley fractionation procedure suggested that the Virginia site has a large pool of organic P in the soil surface. Organic P pools can represent 20-90&37; of the total P present in most mineral soils increasing with the age of the soil (Condron et al., 2005). This increase in organic P pool suggests that biological cycling becomes more important as the stand develops (Wells and Jorgensen 1975). I used solution 31P nuclear magnetic resonance (NMR) spectroscopy to characterize organic P extracted with NaOH-EDTA in the surface of a Paleaquults from coastal Virginia. Total NaOH-EDTA extractable P was significantly larger in the fertilized treatment. Concentrations ranged from 0.1 mg P L&178;-1 in the control plots to 5.1 mg P L&178;-1 in fertilized plots. The surface soils in both treatments were dominated by inorganic orthophosphate. Monoester P compounds were the only organic P compounds detected and were present in very low quantities. The significant increase of NaOH/EDTA extractable P in the soil surface of the VA site suggested there has been a beneficial long-term effect of fertilization similar to the observations from the Mehlich-3 soil test. Results from oxalate loading experiments on ligand exchangeable versus dissolvable P pools in the bulk soil suggested that the long-term effect of P fertilization increased oxalate dissolvable P pools. Plants and microbes have evolved a variety of mechanisms to increase P uptake in low P soil environments. These mechanisms include changes in root morphology and architecture, preferential root growth into high P microsites, the secretion of low-molecular-mass organic acids (LMMOA), and uptake via symbiotic relationships (Fox and Comerford, 1992b&59; Raghothama, 1999&59; Hinsinger, 2001&59; Raghothama, 2005). Results from soil samples taken from the ectomycorrhizal rhizosphere found that loblolly pine mycorrhizal roots modified the soil environment, possibly making recalcitrant P more available. In addition, the long-term effect of fertilization was a 396&37; increase in biologically available P. Fertilization increased loblolly pine volume growth by 57 m&185;3 ha and increased the P content in the litter layer by 118&37;. After the stand was harvested and replanted, mineralization of the litter layer may also increase soil P pools. Results from this long-term fertilization experiment in the Coastal Plain province of Virginia have demonstrated that there has been a significant increase in soil (33.6 kg P ha&178;-1) and biologically available P pools (3.0 kg P ha&178;-1).
Ph. D.

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2

Murphy, Anna Elizabeth. "Effects of commercial clam aquaculture on biogeochemical cycling in shallow coastal ecosystems". W&M ScholarWorks, 2015. https://scholarworks.wm.edu/etd/1539616787.

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As the bivalve aquaculture industry expands worldwide, there is growing interest in its use to mitigate coastal eutrophication, the increased supply of organic matter to an ecosystem. Bivalves influence eutrophication by exerting `top-down' control on primary production through feeding while simultaneously influencing local `bottom-up' effects by increasing nutrient recycling. Additionally, nitrogen (N) is removed via harvest and potentially enhanced denitrification (DNF); however, DNF competes for nitrate (NO3-) with dissimilatory nitrate reduction to ammonium (DNRA), an N retention process. Seasonal in situ flux measurements in Cherrystone Inlet, VA, demonstrated that clam aquaculture sediments are a source of ammonium (NH4+), derived from clam excretion and microbial mineralization of clam biodeposits. Macroalgae, which proliferate on predator-exclusion nets utilized by the US clam industry temporarily sequester this regenerated N. Clam cultivation influences eutrophication locally by providing N in excess of macroalgal N demand, facilitating increased macroalgal production. Experiments investigated the competition between DNF and DNRA within clam sediments. at clam beds in Cherrystone Inlet, DNRA was more favored over DNF than at uncultivated sediments, likely due to the availability of labile organic carbon supplied by clams, low nitrate availability, and sulfidic sediments. However, a comparative study across clam aquaculture sites in the Sacca di Goro, Italy, where Ruditapes philippinarum are cultured, and on the Eastern Shore, VA, where Mercenaria mercenaria are cultured, revealed that the competition between DNF and DNRA is highly dependent on the environment and particularly the relative availability of labile carbon to NO3-. DNF exceeded DNRA at sites in the Sacca di Goro with elevated water column NO3-, concurrent with high abundances of a burrowing amphipod (Corophium sp.) that promoted nitrification. DNRA exceeded DNF at the VA sites and in the eastern region of the Sacca di Goro, where clam biomass was high, water column NO3" low, and sediments were generally reduced. Variability in rates across sites highlights the challenge in generalizing about the role of DNF in enhancing N removal across all clam aquaculture locations. An ecosystem-scale C and N budget was constructed for Cherrystone Inlet to understand the influence of clam cultivation on energy flow and eutrophication at a basin-wide scale. Although clam cultivation occupied only 3% of the Inlet's surface area, the clams filtered a volume equivalent to 7-44% of the system daily. Annually, N regeneration at the clam beds was ~3-fold higher than N removed by harvest. Due to the short water residence time, low watershed N load, and close vicinity of clam beds to the mouth of the Inlet, cultivated clams are likely subsidized by phytoplankton from the Chesapeake Bay. Thus, the N regenerated at the clam beds, which fuels macroalgal production would not be present in the system without facilitation by the cultured clams. This study demonstrates that although clams may dampen eutrophication by removing phytoplankton from the water column, high densities of clams can facilitate rapid N turnover through excretion and DNRA, fueling macroalgae, a form of eutrophication. The effect of clam aquaculture on N removal and subsequently organic matter supply is highly dependent on environmental conditions and clam cultivation practices, as well as the scale considered. at a large-scale (e.g. Chesapeake Bay) clam aquaculture is a net sink for N through harvest, however this study suggests that clam aquaculture may increase N and organic matter supply (i.e. macroalgae) on a basin-wide scale (e.g. Cherrystone Inlet).

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3

Iwasaki, Kenta. "Effects of bedrock groundwater dynamics on hydro-biogeochemical processes in granitic headwater catchments". Kyoto University, 2018. http://hdl.handle.net/2433/232152.

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4

Tritschler, Sarah J. "Biogeochemical Processes and Seasonal Effects in Flow-Through Mesocosm Reactors Simulating Constructed Wetlands". Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1198819178.

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5

Lancaster, Nicole N. M. "Effects of salinity on biogeochemical processes and methylmercury production in freshwater wetland sediments". View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-3//r1/lancastern/nicolelancaster.pdf.

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6

Wilson, Cullen. "Biogeochemical Effects of Lime-Treated Biosolids Amendments on Soils in a Northeastern Forested Ecosystem". Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/WilsonC2008.pdf.

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7

Heinle, Moritz. "The effects of light, temperature and nutrients on coccolithophores and implications for biogeochemical models". Thesis, University of East Anglia, 2013. https://ueaeprints.uea.ac.uk/48676/.

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Coccolithophores are one of the important groups of phytoplankton in the global oceans, which makes it important to know how this group will react to changes in their environment due to climate change. Modellers already recognized their importance and included this group independently in global biogeochemical models. This study assesses the effect of light, temperature and nutrient availability on five coccolithophores, performing a range of laboratory experiments. The results of these experiments were then used to change the parameterisation of coccolithophores in the global biogeochemical model PlankTOM10. Furthermore, the model was validated in two ways, using a database of coccolithophore biomass measurements from the field and measurements of surface calcium carbonate derived from satellite data. Temperature effects on growth depend a great deal on the coccolithophore species. E. huxleyi (both, a subtropical and a temperate strain) and P. carterae grew best around 20°C, whereas G. oceanica and C. leptoporus had optimum temperatures above 25°C and still grew well at the maximum temperature tested in the experiments. E. huxleyi was the species with the highest growth rates (μmax=0.98 for the subtropical strain and μmax=0.97 for the temperate), followed closely by G. oceanica and C. leptoporus (μmax=0.91 in both species). P. carterae (μmax=0.77) had a noticeably lower maximum growth rate than the other coccolithophores. An inverse relationship with growth rate was found for all measured cellular components (POM, PIC, Chl a) as well as for cell volume in P. carterae. Coccolithophores are good competitors at high light intensities, having optimum growth light intensities above 180 μmol photons m-2 s-1. The temperate strain of E. huxleyi and the species G. oceanica showed the lowest optima at 350 μmol photon III m-2 s-1. C. leptoporus (Iopt=500 μmol photon m-2 s-1) and P. carterae (Iopt=600 μmol photon m-2 s-1) had higher optimum growth light intensities and the subtropical strain of E. huxleyi (Iopt=900 μmol photon m-2 s-1) grew best at the highest light intensity applied in this study. Only one strain of E. huxleyi showed light inhibition in its photosynthetic activity that was well above the detection limit in P-I curves up to 2000 μmol photons m-2 s-1. Apart from a well-known decrease in Chl a/C ratio with increasing light intensity, little variation in the concentration of cellular components (POM, PIC) was observed. Nutrient experiments were carried out in a chemostat with two strains of E. huxleyi and one G. oceanica. Phosphorus limitation led to an increase in cell volume (112- 157%) and particulate organic carbon (21-54%) in E. huxleyi and G. oceanica, relative to cultures grown under nitrogen limitation. Comparison of uptake rates for phosphate and nitrate with other phytoplankton groups showed that both species are very good competitors for phosphate and relatively poor competitors for nitrate. The initial PlankTOM10 model simulation overestimated biomass compared with a new observational database, and underestimated surface calcium carbonate compared with satellite data. Changing the coccolithophore parameterisation in PlankTOM10, based on the laboratory results, did not lead to significant improvements relative to the observations. However, the response of the model to the parameter changes could be explained either directly from the changed parameters, or indirectly from changes in the model ecosystem.

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8

Colson, Christopher G. Lockaby Bruce Graeme. "Biogeochemical effects of silviculture management on intermittant streamside management zones in the coastal plain of Alabama". Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Forestry_and_Wildlife_Sciences/Thesis/Colson_Christopher_20.pdf.

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9

Trentman, Matthew T. "Biotic and abiotic effects on biogeochemical fluxes across multiple spatial scales in a prairie stream network". Thesis, Kansas State University, 2015. http://hdl.handle.net/2097/19750.

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Master of Science
Division of Biology
Walter K. Dodds
Understanding the variability of ecological processes across spatial scales is a central issue in ecology, because increasing scale is often associated with increasing complexity. In streams, measurements of biogeochemical fluxes are important for determining ecosystem health and the downstream delivery of nutrients, but are often collected at scales with benthic areas measured in spatial areas from ~10 cm[superscript]2 to ~100 m[superscript]2 (referred to here as patch and reach, respectively), which are smaller than the scale that management decisions are made. Both biotic and abiotic factors will be important when attempting to predict (i.e. scale) biogeochemical rates, but few studies have simultaneously measured rates and their primary drivers at different spatial scales. In the first chapter, I used a conceptual scaling framework to evaluate the ability to additively scale biogeochemical rates by comparing measurements of ecosystem respiration (ER) and gross primary production (GPP) from patch to reach-scales across multiple sites over a two-year period in a prairie stream. Patch-scale measurements with and without fish (biotic factors) and abiotic factors measured simultaneously with metabolic rates suggest that abiotic conditions are stronger drivers of these rates. Patch-scale rates significantly overestimated reach rates for ER and GPP after corrections for habitat heterogeneity, temperature and light, and a variety of stream substrata compartments. I show the importance of determining abiotic and biotic drivers, which can be determined through observational or experimental measurements, when building models for scaling biogeochemical rates. In the second chapter, I further examined patch-scale abiotic and biotic drivers of multiple biogeochemical rates (ER, GPP, and ammonium uptake) using path analyses and data from chapter 2. Total model-explained variance was highest for ER (65% as R[superscript]2) and lowest for GPP and ammonium uptake (38%). Fish removal directly increased ammonium uptake, while all rates were indirectly affected by fish removal through changes in either FBOM and /or algal biomass. Significant paths of abiotic factors varied with each model. Large-scale processes (i.e. climate change and direct anthropogenic disturbances), and local biotic and abiotic drivers should all be considered when attempting to predict stream biogeochemical fluxes at varying spatial scales.

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10

Spencer, David. "The Effects of Oceanographic Drivers on the Catchability of Spanner Crabs". Thesis, Griffith University, 2018. http://hdl.handle.net/10072/380993.

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The world’s largest commercial spanner crab (Ranina ranina) fishery, situated on the east coast of Australia, is showing signs of a fishery-wide population decline. This trend has become ubiquitous in many global fishery stocks and is most commonly attributed to anthropogenic pressure and the rapidly changing climate. Thus, the importance of better understanding how commercially-important fishery species thrive in their immediate and surrounding environment is imperative. Catchability is an important parameter used to describe the relationship between catch rates and the abundance of the target species. Variations in catchability are often attributed to fluctuations in environmental and oceanographic conditions in the species’ preferred habitat. Earlier research had suggested several hydrodynamic and hydrographic parameters affect the catchability of spanner crabs. However, a review of the literature (thesis chapter 2) indicated the need for further investigations, particularly on the specific oceanographic processes responsible for these effects. This thesis examines the effects of several oceanographic parameters on spanner crab catch rates at a range of spatiotemporal scales. At large spatial scales (100:500 km) over several years, higher surface chlorophyll-a concentrations, relative to the range of chlorophyll-a observed in each management region, were correlated with lower catch rates in fishing grounds close to the coast and bays. Additionally, region-specific processes responsible for bringing oceanic waters into spanner crab fishing grounds were associated with an increase in catch rates. The link between oceanic water and increased catch rates was further supported by a more localised study (~100 km) that showed cooler ambient temperatures, occasionally attributed to wind-driven upwelling, increased catch rates of spanner crabs at both seasonal and shorter (days-months) temporal scales. At various fishing locations off the Gold Coast, Australia, the effects of current speed, direction and turbidity were examined to determine how specific conditions (day to day) and changes in conditions during soak times (hours) affected catch rates. The most significant finding from this work suggests that catch rates of spanner crabs benefit from a specific range of current speeds (~0.07-0.12 m.s-1), and current speeds exhibiting a large amount of variability may trigger a spike in catch rates over a period of hours. Results from this work show current speed can help explain short-term catch rate anomalies that are currently deemed “random” in stock assessment models. Incorporating environmental and oceanographic parameters into stock assessment models has been an ever-evolving challenge for fishery management. Depending on the region-specific oceanographic and coastal processes, various remotely-sensed oceanographic parameters are also useful in explaining catch rates. The most significant outcomes from this thesis indicate bottom temperature, alongshore wind stress, and bottom current speed are suitable in explaining variability in spanner crab catch rates. A coupled hydrodynamic and biogeochemical model capable of resolving and predicting fluctuations in these oceanographic parameters will help support studies in other areas of the Australian fishery and smaller fisheries in the Indo-Pacific, help improve the accuracy of stock assessment models, and greatly benefit the economic efficiency of commercial crabbing operations.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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11

Sett, Scarlett [Verfasser]. "Interactive effects of ocean acidification and warming on marine phytoplankton - from physiology to biogeochemical cycling / Scarlett Sett". Kiel : Universitätsbibliothek Kiel, 2014. http://d-nb.info/1058857525/34.

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12

Egan, Gary. "Understanding the functioning of managed grassland ecosystems : evidence of strong liming effects on multiple soil biogeochemical properties". Thesis, Ulster University, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.744766.

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Human-managed grasslands deliver a wide range of ecosystem services including food production and the regulation of nitrogen (N) and carbon (C) cycles between aboveground and belowground compartments. Common management practices, however, such as animal grazing, agricultural liming and nutrient fertilization can greatly influence the functioning of grassland ecosystems and reduce their long-term sustainability. This PhD study has specifically addressed how grazing, liming and nutrient additions might affect soil biogeochemistry and aboveground-belowground interactions in a grassland experiment established in 1991 at Silwood Park, Berkshire, UK. Key findings from this study show how repeated liming applications have significantly (1) increased archaeal and bacterial (B) abundance while reducing fungal (F) abundance, (2) increased the C pool of soil smaller soil aggregate fractions (e.g. micro and silt clay aggregates), and (3) enhanced plant nitrogen use efficiency (NUE). Chronic nutrient fertilization has also significantly increased the abundance of ammonia oxidizing bacteria and decreased plant NUE. A novel result of this study is no change in Fungal and Bacterial gene copies in response to multiple nutrient additions. This suggests that fungal taxa are benefitting from labile resources and not all functional bacterial groups are benefitting from an increase in labile resources returned to the soil. These findings are state of the art and in line with papers that are questioning the classic model of the soil food web where bacteria predominantly metabolise labile detritus and fungi predominantly metabolise recalcitrant detritus. These resources were thought to form part of two distinct basal energy channels, however, the findings in this study support an emerging conceptual framework that understands the food web to have one continuous C pool that can at different times benefit both bacteria and fungi.

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13

Felzer, Benjamin Seth, John M. Reilly, Jerry M. Melillo, David W. Kicklighter, Chien Wang, Ronald G. Prinn, Marcus C. Sarofim e Qianlai Zhuang. "Past and Future Effects of Ozone on Net Primary Production and Carbon Sequestration Using a Global Biogeochemical Model". MIT Joint Program on the Science and Policy of Global Change, 2003. http://hdl.handle.net/1721.1/4053.

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Exposure of plants to ozone inhibits photosynthesis and therefore reduces vegetation production and carbon sequestration. Simulations with the Terrestrial Ecosystem Model (TEM) for the historical period (1860-1995) show the largest damages occur in the eastern U.S., Europe, and eastern China, with reductions in Net Primary Production (NPP) of over 70% for some locations. Scenarios through the year 2100 using the MIT Integrated Global Systems Model (IGSM) show potentially greater negative effects in the future. In the worst-case scenario, the current land carbon sink in China could become a carbon source. Reduced crop yields resulting from ozone damage are potentially large but can be mitigated by controlling emissions of ozone precursors. Failure to consider ozone damages to vegetation would by itself raise the costs over the next century of stabilizing atmospheric concentrations of CO2 by 3 to 18%. But, climate policy would also reduce ozone precursor emissions, and ozone, and these additional benefits are estimated to be between 4 and 21% of the cost of the climate policy. Tropospheric ozone effects on terrestrial ecosystems thus produce a surprisingly large feedback in estimating climate policy costs that, heretofore, has not been included in cost estimates.
Abstract in HTML and technical report in PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/).
This study was funded by the Biocomplexity Program of the U.S. National Science Foundation (ATM-0120468), the Methods and Models for Integrated Assessment Program of the U.S. National Science Foundation (DEB-9711626) and the Earth Observing System Program of the U.S. National Aeronautics and Space Administration (NAG5-10135). We also received support from the federal and industrial sponsors of the MIT Joint Program on the Science and Policy of Global Change.

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14

Chow, Stephanie Stacey. "Effects of Biogeochemical and Physical Processes on the Transformation of Trace Metals at Oxic-Anoxic Interfaces in Aquatic Systems". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19705.

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Trace metals (e.g. Fe, Mn, Zn, Cu, Cd, Ni) are important micronutrients that have historically been regarded as toxic pollutants rather than essential components of riverine and estuarine environments. The toxicity and behavior of trace metals, in response to physical and biogeochemical processes, are determined by their individual physico-chemical properties. In this dissertation, the vertical transformation of trace metals across oxic-anoxic interfaces was investigated at two sites, a Fe-rich freshwater river with minimal sulfide and an estuary with elevated Mn and H2S concentrations. Sediment profiles obtained from the Chattahoochee River showed that dissolved arsenic, present as As(V) only, is scavenged by Fe-oxides and accumulates directly below the sediment-water interface. Depth profiles also indicate that As(V) fluxes into the overlying water during baseflow conditions as well as after storm events. The significant correlation between Fe(II) and As(V) suggest that As(V) is released from Fe-oxides during their microbial reduction. By implementing a series of sediment incubations under increasing As(V) loads, it was determined that adsorption onto Fe-oxides and microbially mediated reductive dissolution of these mineral phases drive arsenic cycling in this sediment. These incubations also reveal for the first time that arsenic, even in low concentrations, n turn, arsenic loading impacts iron cycling by stimulating anaerobic respiration of Fe-oxides and promoting recrystallization of authigenic Fe-oxides, up to a toxicity threshold up to a few micromolar in concentrations. A combination of in situ measurements with discrete water sampling was utilized to determine the effects of tidal cycling on the distribution of trace metals under changing redox conditions during two consecutive tidal cycles at Station 858 in the Chesapeake Bay. Estuarine circulation patterns driven by tidal oscillations, a defined pycnocline, and the shallow sill (~20 m) of the Chesapeake Bay promoted bottom water anoxia during the summer months that allowed dissolved sulfide and reduced manganese to accumulate below the oxycline. The distribution of barium (conservative freshwater tracer) and uranium (conservative seawater tracer) across the pycnocline over the two tidal cycles indicated that the source of dissolved species was surficial sediments. During ebb and flood tides, the shear stress from the bottom waters flowing over the sediment seems to episodically promote the advection of porewaters enriched in dissolved sulfide, manganese, uranium, barium, lead, chromium, and copper. The selective enrichment of these trace metals appears to be controlled by their reactivity with sulfide. In contrast, cobalt and nickel are retained in sediments by adsorbed or incorporated in FeS and FeS2, while arsenic co-precipitates with sulfide or iron sulfide minerals. Overall, this study demonstrates that natural aquatic systems are complex environments where the interplay between biological, chemical, and physical processes affects the distribution of trace metals over short time scales. While a great wealth of knowledge can be obtained by laboratory experiments with synthetic solutions or pure cultures of organisms, a combination of in situ measurements and incubations with real samples in necessary to characterize the processes regulating the cycling of trace metals in aquatic systems.

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15

Taucher, Jan [Verfasser]. "Effects of increasing temperatures and CO2 on phytoplankton and marine biogeochemical cycles – combining experimental work and numerical modeling / Jan Taucher". Kiel : Universitätsbibliothek Kiel, 2013. http://d-nb.info/1045859044/34.

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16

Traub, Eric Leonard. "The Effects of Biogeochemical Sinks on the Mobility of Contaminants in an AreaAffected by Acid Mine Drainage, Huff Run, Ohio". Kent State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=kent1461603659.

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17

Diop, Souleymane. "Dynamique de l'albédo de surface et bénéfice climatique de l'agriculture de conservation au Zimbabwe sub-humide". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASB066.

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L'agriculture de conservation (AC) est une des solutions basées sur la nature offrant des perspectives intéressantes en termes de leviers d'atténuation et de stratégies d'adaptation au changement climatique. En Afrique subsaharienne, les études des potentiels d'atténuation des changements climatiques par l'AC se concentrent sur les effets biogéochimiques (stockage C, emissions de GES) tandis que les effets biogéophysiques (effets albédo, flux d'énergie) sont souvent ignorés. Dans ce contexte, il est très pertinent d'approfondir les effets de l'AC sur les contributions biogéophysiques de l'agriculture sur le climat afin d'identifier les potentiels leviers d'atténuation associés aux changements de pratiques et les possibles synergies avec les effets biogéochimiques. Nous avons mené des études de quantification des effets biogéophysiques à travers des mesures d'albédo de surface, de rayonnement thermique, de température de surface, de contenu en eau dans le sol, et de dynamiques de croissance des cultures durant deux années culturales au Zimbabwé sur deux types de sol contrasté : un Lixisol abruptique sableux et clair et un Ferralsol xanthique argileux et sombre. Trois pratiques culturales sont comparées dans cette études : le labour conventionnel (CT, pour Conventional Tillage en anglais), la suppression du labour (NT pour No-Tillage en anglais) et le maintien des résidus en surface (NTM pour No-Tillage with Mulch en anglais). Les résultats ont montré une augmentation d'albédo de surface suite à l'adoption de la pratique du NT comparé au CT quel que soit le type de sol. L'apport des résidus de culture en surface comparé au CT à des effets contrasté suivant les types de sol. En effet, les résidus contribuent à une augmentation de l'albédo de surface sur les sols argileux sombres et contribuent à sa diminution sur les sols sableux clairs. Ces changements d'albédo ont entraîné des forçages radiatifs négatifs associés à un effet refroidissant sur le climat du NT quel que soit le type de sol et des effets contrastés pour le NTM, avec un effet refroidissant sur les sols argileux foncés et un effet réchauffant sur les sols sableux clairs. Nous avons comparé ces forçages radiatifs induits par l'albédo de surface aux effets biogéochimiques du stockage de carbone (C) et des émissions de N2O induits par ces mêmes pratiques. Les résultats obtenus ont montré que sur 30 ans de pratique d'AC, les changements d'albédo liés aux pratiques NT et NTM ont des effets climatiques allant de -1,27 à +1,15 t CO2-éq ha⁻¹ an⁻¹, comparables au potentiel de stockage de carbone dans les sols en Afrique subsaharienne. Sur les sols argileux sombres, ces pratiques renforcent l'effet de refroidissement, tandis que sur les sols sableux clairs, elles entraînent un effet réchauffant à court terme, annulant les bénéfices climatiques du C stocké à long terme. Pour mieux comprendre les déterminants des dynamiques d'albédo et être en capacité à les simuler en fonction des pratiques, le modèle STICS a été utilisé, révélant des limites dans la prise en compte de l'effet des tissus sénescents et de l'humidité de surface sur les dynamiques de l'albédo de surface. De nouveaux formalismes ont ensuite été proposés et testés, ce qui a permis d'améliorer les simulations de l'albédo de surface. Cette étude met en avant l'importance d'intégrer les effets biogéophysiques et biogéochimiques pour mieux évaluer les impacts climatiques des pratiques agricoles et optimiser les mesures d'adaptation et d'atténuation
In Sub-Saharan Africa, studies of potential climate change mitigation levers by CA focus more on biogeochemical effects (C storage, GHG emissions) while biogeophysical effects (albedo effects, energy fluxes) are often ignored. In this context, it is very relevant to delve into the effects of CA on agriculture's biogeophysical contributions to climate in order to identify potential mitigation levers associated with changes in practices and possible synergies with the biogeochemical effects. We conducted studies to quantify the biogeophysical effects through measurements of surface albedo, heat radiation, surface temperature, water content in soil, and dynamics of crop growth during two growing years in Zimbabwe on two types of contrasting soil: a sandy, light-coloured abruptic Lixisol and a clayey, dark-coloured xanthic Ferralsol. Three cropping practices are compared in this study: conventional tillage (CT), no-tillage (NT) and no-tillage with mulch (NTM). The results showed an increase in surface albedo following the adoption of NT practice compared to CT regardless of soil type. The contribution of crop residues to surface compared with CT lead to contrasting effects according to soil types. Indeed, the residues contribute to an increase in surface albedo on dark clay soils and contribute to its decrease on light sandy soils. These albedo changes have led to negative radiative forcing associated with a cooling climatic effect on the NT regardless of soil type and contrasting effects for the NTM, with a cooling effect on dark clay soils and a warming effect on light sandy soils. We compared these surface albedo-induced radiative forcings with the biogeochemical effects of carbon (C) storage and N2O emissions induced by these same practices. The results obtained showed that over 30 years of CA practice, albedo changes related to NT and NTM practices have climatic effects ranging from -1.27 to +1.15 t CO2-eq ha-1 year-1, comparable to the potential for carbon storage in soils in Sub-Saharan Africa. On dark clay soils, these practices enhance the cooling effect, while on light sandy soils, they cause a warming effect in the short term, negating the climate benefits of long-term stored C. To better understand the determinants of albedo dynamics and to be able to simulate them according to practices, the STICS model was used, revealing limitations in the consideration of the effect of senescent tissues and surface moisture on the dynamics of surface albedo. New formalisms were then proposed and tested, which allowed to improve the simulations of the surface albedo. This study highlights the importance of integrating biogeophysical and biogeochemical effects to better assess climate impacts of agricultural practices and optimize adaptation and mitigation measures

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18

Lindgren, Georg. "Physical process effects on catchment-scale pollutant transport-attenuation, coastal loading and abatement efficiency". Doctoral thesis, KTH, Mark- och vattenteknik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3900.

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Pollutants follow various subsurface and surface water pathways from sources within a catchment to its outlet and may cause detrimental effects on downstream water quality and ecosystems. Along their different transport pathways through a catchment, pollutants may be attenuated subject to different physical and biogeochemical processes. In this thesis, physical process effects on such catchment-scale pollutant transport and attenuation, resulting coastal pollutant loading and its efficient abatement are investigated. For this purpose, pollutant transport-attenuation is modeled both generically using a Lagrangian Stochastic Advective-Reactive (LaSAR) approach and site specifically for the Swedish Norrström basin using the GIS-based dynamic nitrogen transport-attenuation model POLFLOW. Furthermore, the role of such modeling for catchment-scale pollutant abatement is also investigated by use of economic optimization modeling. Results indicate that appropriate characterization of catchment-scale solute transport and attenuation processes requires accurate quantification of the specific solute pathways from different sources in a catchment, through the subsurface and surface water systems of the catchment, to the catchment outlet. The various physical processes that act on solute transported along these pathways may be quantified appropriately by use of relevant solute travel time distributions for each water subsystem that the pathways cross through the catchment. Such distributions capture the physical solute travel time variability from source to catchment outlet and its effects on reactive pollutant transport. Results of this thesis show specifically that neglect of such physical solute travel time variability in large-scale models of nitrogen transport and attenuation in catchments may yield misleading model estimates of nitrogen attenuation rates. Results for nitrogen abatement optimization in catchments further indicate that inefficient solutions for coastal nitrogen load reduction may result from simplifying physical transport assumptions made in different catchment-scale nitrogen transport-attenuation models. Modeling of possible future nitrogen management scenarios show also that slow nitrogen transport and reversible mass transfer processes in the subsurface water systems of catchments may greatly delay and temporally redistribute coastal nitrogen load effects of inland nitrogen source abatement over decades or much longer. Achievement of the national Swedish environmental objective to reduce the anthropogenic coastal nitrogen loading by 30% may therefore require up to a 40% reduction of both point sources, for achieving a fast coastal load response, and diffuse sources, for maintaining the coastal load reduction also in the long term.
QC 20100908

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19

Schlingmann, Marcus [Verfasser], Michael [Akademischer Betreuer] Dannenmann e Heinz [Akademischer Betreuer] Rennenberg. "Effects of climate change and management on biogeochemical N turnover, slurry N use efficiency and associated pedosphere-atmosphere-hydrosphere exchange of N compounds in montane grasslands". Freiburg : Universität, 2020. http://d-nb.info/1215499183/34.

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20

Fink, Daniel Francis. "Effects of a pulsing hydroperiod on a created riparian river diversion wetland". Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1167401886.

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21

Giessing, Anders Michael Bernth. "Biogeochemical Fate of Sediment-Associated PAH: Effect of Animal Processing". Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/GiessingAMB2002.pdf.

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22

Maguire, Michael Joseph. "Effect of elevated CO2 on marine bacterioplankton and biogeochemical processes". Thesis, University of Newcastle upon Tyne, 2014. http://hdl.handle.net/10443/2727.

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It has been established that ocean acidification will adversely affect calcifying organisms but little is known about its effects on bacterioplankton and the biogeochemical processes which they catalyse. In this thesis, the impact these changes may have on microbialy driven processes is assessed through a mesocosm experiment conducted in a Norwegian fjord near Bergen in May 2006. Three mesocosms were bubbled with CO2(g) to simulate the predicted future conditions of rising atmospheric CO2 concentrations (~760ppm, pH ~7.8), while another three were treated as controls and bubbled with ambient air to represent present day conditions (~380ppm, pH ~8.15). The mesocosms were amended with nitrate and phosphate [16:1] to stimulate a phytoplankton bloom and scientific measurements and analyses were conducted over a 23 day period. At the peak of the phytoplankton bloom chlorophyll-a concentration was ~34% higher under ambient CO2 conditions compared to the high CO2. This was reflected in the flow cytometry results which showed a significant decrease of coccolithophorid and picoeukaryote cell numbers in the high CO2 treatment. Analysis of 16S rRNA gene clone libraries supported by qPCR data revealed that elevated CO2 resulted in a sharp decline in Roseobacter-like bacteria from the Alphaproteobacteria which are significant consumers of the algal osmolyte dimethylsulphoniopropionate (DMSP). Stable isotope probing using 13C labelled sodium bicarbonate revealed that the assimilation of dissolved inorganic carbon by Roseobacter-like bacteria is more prevalent than previously thought making them major contributors to global CO2 fixation. Furthermore, metagenomic analysis of the ambient and high CO2 libraries revealed a significant decrease in genes coding for DMSP demethylase in the high CO2 metagenome. This gene is responsible for the catabolism of DMSP resulting in the eventual release of methanethiol, a source of reduced sulfur for marine bacteria. However, DMSP degradation may proceed down an alternate route known as the lyase pathway resulting in the release of the climatically active gas dimethylsulfide (DMS). In conclusion, the findings of this study strongly suggest that the subsequent decline in Roseobacter species will shift the balance in the degradation of DMSP in favour of the alternate lyase pathway resulting in increased production of DMS and a decrease in the concentration of methanethiol. It is believed that the consequent loss of fixed sulfur will affect ocean productivity and that global climate patterns may change due to the scattering of solar radiation by increased atmospheric sulfur.

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23

Harlay, Jérôme. "Biogeochemical study of coccolithophorid blooms in the context of climate change". Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210352.

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Coccolithophores are unicellular microscopic algae (Haptophyta) surrounded by calcium carbonate plates that are produced during their life cycle. These species, whose contemporary contributor is Emiliania huxleyi, are mainly found in the sub-polar and temperate oceans, where they produce huge blooms visible from space. Coccolithophores are sensitive to ocean acidification that results from the ongoing accumulation of anthropogenic carbon dioxide (CO2) in the atmosphere. The response of these organisms to global change appears to be related to the reduction of their ability to produce calcium carbonate at the cellular level. At the community levels, one anticipates changes in the carbon fluxes associated to their blooms as calcification is reduced. However, the consequences of such environmental changes on this species are speculative and require improvements in the description of the mechanisms controlling the organic and inorganic carbon production and export.

The first aspect of this work was to study the response of these organisms to artificially modified CO2 concentrations representative of the conditions occurring in the past (glacial) and those expected by the end of the century (2100). Two different levels were examined: the continuous monospecific cultures (chemostats) allowed us to work at the cellular level while the mesocosms gave light to the mechanisms taking place in an isolated fraction of the natural community. The second aspect of this work consisted of field studies carried out during four cruises (2002, 2003, 2004 and 2006) in the northern Bay of Biscay, where the occurrence of E. huxleyi blooms were observed in late spring and early summer. We describe the vertical profiles of biogeochemical variables (nutrients, chlorophyll-a, dissolved inorganic chemistry, particulate carbon, transparent exopolymer particles (TEP)) and study processes such as primary production, calcification and bacterial production. The properties of these blooms are compared with those reported in the literature and enriched with original measurements such as the abundance and concentration of TEP that could play an important role in carbon export to the deep ocean, modifying the properties of the settling ballasted aggregates.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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24

Smith, Andrew Robert. "The effect of atmospheric CO2 enrichment on biogeochemical cycling of temerate forest ecosystems". Thesis, Bangor University, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531049.

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25

Stanley, Nicolette. "Effect of various biogeochemical processes on mercury methylation in copper-zinc and gold mine tailings". Thesis, University of Ottawa (Canada), 2005. http://hdl.handle.net/10393/27043.

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Abstract (sommario):

Mercury is a well known environmental pollutant. Anthropogenic sources include coal combustion, waste incineration and metal processing. In base metal mines, Hg is often left in the mining wastes (i.e., mine tailings). Once disposed of in open-air impoundments, these Hg-containing tailings can undergo various biogeochemical transformations, including Hg methylation. It is the methylated form of mercury (MeHg) that poses a threat to the environment, because it bio-accumulates at each level of the food chain. The present study was undertaken to assess the biogeochemical factors affecting Hg methylation in Cu-Zn and Au mine tailings. The study focused on the role of sulfate-reducing bacteria (SRB) because they are suspected to be associated with Hg methylation. Temperature, sulfate and organic carbon availability, along with SRB activity were tested as potential factors affecting Hg methylation in column experiments containing old Au tailings and fresh Cu-Zn tailings. The results first showed that SRB activity did not enhance Hg methylation in Cu-Zn tailings and Au tailings, indicating that iron reducing bacteria, and not SRB, along with abiotic methylation reactions played an important role. Cold temperatures did not slow down SRB activity and MeHg production, but the accidental freezing and thawing of the Cu-Zn tailings promoted the production of soluble MeHg. The mechanism responsible for this unexpected Hg methylation is however unknown. Elevated organic carbon and sulfate concentrations did enhance SRB activity, but not MeHg formation in the tailings, because increased sulfide production hindered Hg methylation. Tailings mineralogy played a significant role in the production of methyl mercury, Au tailings contained more soluble and solid-bound MeHg than Cu-Zn tailings. These results add to the increasing amount of information on Hg cycling in the environment, and indicate that SRB might not be the dominant Hg methylators in mining environments.

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26

Elias, Eltijani Abdelrahiem. "Studies of aspects of biogeochemical cycling, with particular reference to soil sustainability and to the sea-salt effect". Thesis, University of Aberdeen, 1996. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU083052.

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The concept of soil sustainability has been concisely reviewed, to show the central role of biogeochemical cycling in sustaining fertility of both natural and managed soils. The role of sea salt inputs from the atmosphere within the context of biogeochemical cycling of base cations, concentrating upon the ameliorative effects that base cation inputs from the atmosphere may have against soil acidification in acidification-sensitive upland soils in Scotland, is then discussed more fully. Three approaches were used to try to confirm the importance of the sea salt effect to Scottish upland soils. Studies under controlled laboratory conditions provided strong evidence that maintaining soils under field moist conditions caused considerable increases in exchangeable Ca2+:Na + ratios, which could be attributed to internal soil action redistributions in the absence of a sea salt input. The changes in soil pH over time were not as simple as had been initially expected, partly as a consequence of the complications caused by organic matter oxidation. This study clearly showed it is unwise to store field moist soils in a cooled room for a few weeks prior to analysis. Samples stored for 20 months were re-analysed to look for effects that could be attributed to the elimination of sea salt inputs, but the results did not provide evidence for a sea salt effect. Interpretation was difficult because of the possibility of errors occurring as a result of soil storage in a cold room for up to a few weeks prior to soil analysis, and the high degree of organic matter oxidation. The latter results in release of SO42-, which was removed by precipitation of aluminium sulfate. Repacked soil columns containing individual soil horizons were subjected to simulated high sea salt and low sea salt rainfall treatments over three months. One set of soil horizons was pre-treated to remove organic matter. The results of this experiment were much more unequivocal, with large increases in exchangeable Na+ and Mg2+ concentrations and corresponding soil pH shifts. Finally, it was hypothesised that, if soils with low mineral weathering rates in north east Scotland were susceptible to strong sea salt effects, this should be reflected directly in the associated river water composition. This was confirmed experimentally, and there was a strong link between susceptibility to sea salt effects and susceptibility to acidification.

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27

Lin, Hui. "Anaerobic reduction of manganese oxides and its effect on the carbon and nitrogen cycles". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/47625.

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The biogenic reduction of Mn(IV) oxides is one of the most favorable anaerobic electron transfer processes in aquatic systems and likely plays an important role in the redox cycle of both carbon and nitrogen in anaerobic environments; yet, the different pathways involved in the microbial transformation of Mn(IV) oxides remain unclear. The coupling between the reduction of Mn(IV) to Mn(II) and the oxidation of organic carbon to CO₂ is largely catalyzed by microorganisms in various environments such as redox stratified water columns and sediments. The recent discovery that soluble Mn(III) exists in natural systems and is formed during biological oxidation of Mn(II) implies the possibility that Mn(III) is formed as an intermediate during the microbial reduction of Mn(IV). In this dissertation, mutagenesis studies and kinetic analysis were combined to study the mechanism of microbial reduction of Mn(IV) by Shewanella oneidensis MR-1, one of the most studied metal-respiring prokaryotes. We show for the first time that the microbial reduction of Mn(IV) proceeds step-wise via two successive one-electron transfer reactions with soluble Mn(III) as intermediate produced in solution. The point mutant strain Mn3, generated via random chemical mutagenesis, presents a unique phenotype that reduces solid Mn(IV) to Mn(III) but not to Mn(II), suggesting that these two reduction steps proceed via different electron transport pathways. Mutagenesis studies on various in-frame deletion mutant strains demonstrate that the reduction of both solid Mn(IV) and soluble Mn(III) occurs at the outer membrane of the cell and Mn(IV) respiration involves only one of the two potential terminal reductases (c-type cytochrome MtrC and OmcA) involved in Fe(III) respiration. Interestingly, only the second electron transfer step is coupled to the respiration of organic carbon, which opposes the long-standing paradigm that microbial reduction of Mn(IV) proceeds via the single transfer of two electrons coupled to the mineralization of carbon substrates. The coupling between anaerobic nitrification and Mn reduction has been demonstrated to be thermodynamically favorable. However, the existence of this process in natural system is still in debate. In this dissertation, characterization of coastal marine sediments was combined with laboratory incubations of the same sediments to investigate the effect of Mn oxides on the redox cycle of nitrogen. Our slurry incubations demonstrate that anaerobic nitrification is catalyzed by Mn oxides. In addition, mass balance calculations on NH₄⁺ link the consumption of NH₄⁺ to anaerobic ammonium oxidation in the presence of Mn oxides and confirm the occurrence of Mn(IV)-catalyzed anaerobic nitrification. The activity of anaerobic nitrification is greatly affected by the initial ratio of Mn(IV) to NH₄⁺, the reactivity of Mn oxides, and the reducing potential of the system. Overall, Mn(IV)-catalyzed anaerobic nitrification may be an important source of nitrite/nitrate in anaerobic marine sediments and provide an alternative pathway for subsequent nitrogen losses in the marine nitrogen cycle.

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28

Bristow, Gwendolyn. "The effect of tidal forcing on iron cycling in intertidal salt marsh sediments". Thesis, Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-07102006-112540/.

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Thesis (M. S.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2007.
Dr. Emanuele Di Lorenzo, Committee Member ; Dr. Ellery Ingall, Committee Member ; Dr. Martial Taillefert, Committee Chair.

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29

Kirchen, Gil. "Effet du type de sol sur le fonctionnement biogéochimique des écosystèmes forestiers". Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0308/document.

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Cette thèse porte sur l’impact du type de sol sur le fonctionnement biogéochimique d’un écosystème forestier typique d’Europe centrale et occidentale. Pour cette étude, un dispositif expérimental a été mis en place par l’INRA et l’ANDRA au sein d’une hêtraie (Fagus sylvatica) dans la forêt de Montiers-sur-Saulx (Meuse, France) afin de suivre les cycles biogéochimiques entre les différents compartiments de l’écosystème (l’atmosphère, la canopée, la litière et le sol). L’intérêt particulier du site expérimental de Montiers vient du contraste important entre les types de sols pour un même peuplement : rendisol, calci-brunisol et alocrisol/brunisol. Pour la première fois, les stocks et les flux de l’eau et des éléments ont été mesurés et comparés in situ et sur le long terme (entre janvier 2012 et décembre 2015) sur des sols forestiers différents, toutes les autres conditions du site égales par ailleurs (climat, apports atmosphériques, âge et structure du peuplement). Les stocks totaux et échangeables dans le sol et les stocks dans les différents compartiments de la biomasse végétale (branches, tronc, racines grosses et fines) ont été déterminés par le biais d’analyses chimiques et de modélisations. Les flux élémentaires ont été calculés à partir des prélèvements mensuels des solutions de l’écosystème (dépôt atmosphérique, pluviolessivat, écoulement de tronc, solutions libres et liées du sol) et des chutes de litière. Le modèle hydrique BILJOU© a été utilisé pour estimer les composantes du bilan hydrique de l’écosystème. Les résultats montrent que la réserve utile du sol, les stocks des éléments dans le sol, les compositions chimiques des solutions du sol, la stratégie de colonisation racinaire et la production de biomasse pérenne diffèrent fortement en fonction du type de sol. Contrairement à ce que l’on pouvait supposer compte tenu des différences marquées entre les signatures chimiques des solutions des trois sols, les compositions foliaires du peuplement et les flux des éléments hors sol en solution (échange de la canopée, apport au sol) et sous forme solide (chute de litière) ne diffèrent pas ou peu entre les trois stations expérimentales pour la majorité des éléments. La part biologique des cycles minéraux est globalement prédominante et le renouvellement des racines fines représente un flux de recyclage généralement supérieur à la chute de litière aérienne. Nous montrons également que la quantité d’eau transpirée par la canopée, directement liée à la taille de la réserve utile du sol, est le facteur de contrôle principal de la productivité du peuplement à l’échelle annuelle. Des processus d’adaptation du peuplement aux conditions physico-chimiques du sol semblent réduire, voire compenser entièrement, les facteurs secondaires de contrôle de la productivité du peuplement (notamment la disponibilité des nutriments dans le sol). Ainsi un enjeu significatif pour les gestionnaires forestiers pourrait être l’adaptation des pratiques sylvicoles à des parcelles de gestion davantage basées sur les propriétés physiques des sols, et en particulier les profondeurs d’apparition de la roche-mère et de colonisation racinaire
This thesis deals with the impact of soil type on the biogeochemical functioning of a typical forest ecosystem of Central and Western Europe. For this study, a strongly instrumented experimental site was implemented in a beech stand (Fagus sylvatica) within the state forest of Montiers-sur-Saulx (Meuse, France), in order to monitor the biogeochemical cycling between the different compartments of the ecosystem (the atmosphere, the canopy, the forest floor and the soil). The particular value of the Montiers experimental site resides in the strong contrast between soil types under the same beech stand: Rendzic Leptosol, Eutric Cambisol and Dystric Cambisol. For the first time, stocks and fluxes of water and elements were measured and compared in situ and over the long term (from January 2012 to December 2015) on different forest soil types, all other site conditions being equal (climate, atmospheric inputs, stand age and structure). Total and exchangeable pools in the soil and stocks in the different compartments of the vegetation (branches, trunk, fine and coarse roots) were determined via chemical analysis and modelisation. Fluxes of elements were calculated from monthly sampling of the ecosystem’s solutions (atmospheric deposition, throughfall, stemflow, gravitational and bound soil solutions) and of litter fall. The water balance model BILJOU© was used to estimate the different components of the water budget. The results show that the soil water holding capacity, the stocks of elements in the soil, the chemical composition of soil solutions, the rooting strategy and the perennial biomass production differ strongly between soil types. Contrary to what might have been expected in regard to the marked differences between the chemical signatures of the soils solutions in the three soils, the foliar elemental composition of the beech stand and the aboveground fluxes of elements in solution (canopy exchange, stand deposition) and in solid state (litter fall) do not differ significantly between the three experimental stations for the majority of the studied elements. The biological part of the mineral cycles is overall predominant and the recycling through fine roots turnover is generally higher than litter fall. We also show that the quantity of water transpired by the forest canopy, directly linked to the soil water holding capacity, is the primary control factor of the annual stand productivity. Stand adaptation mechanisms to physico-chemical soil properties seemed to reduce, or even entirely compensate for, secondary factors controlling the stand productivity (in particular nutrient availability in the soil). Thus a significant issue for forest managers might be to further adapt forestry practices to management units based on soil physical properties, especially depth to the bedrock and rooting depth

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30

Poblete-Grant, Patricia Victoria. "Impact of poultry manure application, alone or combined with phosphate rock on biogeochemical cycling of C and P in grassland soils". Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS294.

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Les fertilisants phosphatés sont issus de sources de phosphate minéral (RP) non renouvelables. Dans le futur, il a été mis en évidence une raréfaction de ces sources due à de forts besoins d’augmentation des rendements visant à l’alimentation de la population mondiale grandissante. Des alternatives avec l’utilisation de sources de phosphore (P) inorganique sont encouragées pour promouvoir la durabilité des systèmes agricoles. Cette thèse a été réalisée afin d’estimer l’impact de l’application de fumier de volaille (PM), seul ou combiné avec du PM, sur la qualité du sol, la séquestration du carbone (C), la disponibilité du P et la production de ray-grass. Des échantillonnages sur quatre fermes amendées sur le long terme avec du PM composté ont été effectués et une expérience en laboratoire à l’aide de marquage au 13C utilisant du compost de PM, du RP et une combinaison des deux (PMRP) sur la croissance de ray-grass sur deux types de sol a été réalisée. Ce travail de recherche a montré que les applications sur le long terme de composts de PM au champ augmentent significativement la teneur en C organique du sol. En favorisant les particules de grandes tailles via des applications de PM, on augmente la teneur en C organique du sol et le P disponible. Par ailleurs, l’expérience de laboratoire permet de montrer que la combinaison de PM et de RP a un effet positif sur la disponibilité du P dans les deux types de sol, alors que concernant les paramètres liés aux plantes, les effets synergétiques et antagonistes étaient, eux, dépendants du type de sol. Cette étude indique clairement que le compost de PM et sa combinaison avec le RP appliqué dans deux types de sols augmente la teneur en C organique du sol ainsi que le C organique labile. D’avantage d’expérimentations de terrain sont nécessaires pour rendre compte de manière réaliste et efficace de l’effet du PM seul et combiné avec des RP pour déterminer à long terme la stabilisation du C et la disponibilité du P, incluant les paramètres de productivité et de qualité des cultures
Phosphate fertilizers are manufactured from the non-renewable phosphate rock (RP) sources. In the future, it has been prospected a scarcity of this sources due to its high demand to enhance crops yields for feeding the growing world population. Alternatives in the use of inorganic phosphorus (P) sources are encouraged to promote the sustainability in agricultural systems. This thesis project was performed to assess the impact of poultry manure (PM) application, alone or combined with RP, on soil quality, carbon (C) sequestration, P availability and ryegrass production. We sampled four different farms amended with long-term PM compost and, also, we performed a 13C labelled laboratory experiment using PM compost, RP, and their combination (PMRP) on ryegrass plants grown on two soil types. Our research showed that soils receiving long-term PM compost increased significantly SOC content. Promoting larger particle size by PM led to an increase on SOC and available P. On the other hand, from the laboratory experiment we reported that the combined use of PM and RP, showed a positive effect for soil available P in both soils, while for plant parameters, synergistic and antagonistic effects were soil type dependent. Our study clearly indicated that both PM compost and its mixture with RP applied in two different soil types increased total SOC and labile organic C. Moreover, the greatest contribution to stored SOC were observed as PM compost-derived C. Further field experiments are needed to account realistic and effective effect of PM alone and its mixture with RP to assess long-term soil C stabilization and P availability, including plant productive and quality parameters

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Corti, Roland. "Assèchement des cours d'eaux : effets sur les communautés d'invertébrés et la dynamique de la matière organique particulaire". Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10048/document.

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Les transitions terrestre-aquatique jouent un rôle primordial dans le fonctionnement des écosystèmes. Dans les cours d'eau qui cessent de s'écouler périodiquement, ces transitions se développent latéralement au travers des zones ripariennes mais aussi longitudinalement le long du lit du cours d'eau. L'objectif de ce travail de thèse était de déterminer les effets de ces transitions terrestre-aquatique dans les lits des cours d'eau sur les communautés d'invertébrés terrestres et sur dynamique de la matière organique particulaire, un processus écologique fondamental au fonctionnement des cours d'eau. Les résultats montrent que communautés d'invertébrés ripariens sont peu dépendantes des ressources aquatiques du cours d'eau mais sont essentielles au maintien de la diversité en invertébrés dans les lits asséchés. La matière organique est transportée et se décompose par à coup lors des conditions aquatiques, influençant potentiellement la disponibilité en nutriments dans les réseaux hydrographiques
Aquatic-terrestrial transitions play a major role in the functioning of ecosystems. In rivers that periodically cease to flow, these transitions move laterally in riparian zones and longitudinally along dry riverbeds. The objective of this thesis was to determine in drying rivers the effects of aquatic-terrestrial transitions on terrestrial invertebrate communities and on particulate organic matter dynamic, a key ecological process for ecosystem functioning. The results show that riparian communities are poorly dependent on aquatic resources from the rivers but are essential to invertebrate diversity in dry riverbeds. Organic matter has a pulsed dynamic in drying rivers with transport and processing stages limited to aquatic conditions, potentially influencing nutrient availability in river networks

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Lochon, Iris. "Effets du chaulage sur le fontionnement de l'écosystème prairial en moyenne montagne". Thesis, Université Clermont Auvergne‎ (2017-2020), 2018. http://www.theses.fr/2018CLFAC053/document.

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La mise en place d’une agriculture plus durable nécessite une compréhension de l’impact des pratiques de gestion sur le fonctionnement des agroécosystèmes et sur la fourniture de services écosystémiques. En représentant près de 68% des terres agricoles mondiales et contribuant à la subsistance de plus de 800 millions de personnes, les prairies sont l’un des agroécosystèmes où l’optimisation des pratiques agricoles apparaît comme cruciale. Ce travail de thèse porte sur le chaulage, une pratique agricole connue pour lutter contre les effets de l’acidification des sols – qu’elle soit naturelle ou induite par la gestion – mais dont l’efficacité est variable en prairie permanente. De fait, la littérature documentant l’impact du chaulage en prairie permanente est limitée et ne prend en compte que rarement la multifonctionnalité de ces agroécosystèmes. Par une approche intégrant différents types d’expérimentations, mon travail de thèse a cherché à répondre à ce besoin et à renforcer les connaissances du chaulage sur le fonctionnement de l’écosystème prairial. Le développement d’expérimentations au champ (in situ), en conditions semi-contrôlées (mésocosmes) et d’incubations de sol au laboratoire (microcosmes) a permis d’explorer les effets du chaulage sur les différents compartiments de l’écosystème prairial (végétation, microorganismes, sol) ainsi que l’influence de facteurs modulant ces effets. Dans l’ensemble des expérimentations, le chaulage a effectivement augmenté le pH des sols. Toutefois, cette amélioration du statut acido-basique du sol ne s’est pas toujours traduite par une augmentation de la productivité du fourrage ou des biomasses microbiennes et racinaires. Mes travaux ont montré que le chaulage contribue aux émissions de gaz à effet de serre par différentes voies (réémission du carbone apporté sous forme de chaulage et stimulation de la minéralisation) et peut potentiellement réduire les émissions de CO2 à l’échelle de la respiration de l’écosystème. Collectivement mes résultats soulignent l’importance du contexte pédoclimatique sur l’impact du chaulage en prairie permanente, et la difficulté d’extrapoler les effets du chaulage, en particulier sur la production de fourrage et les émissions de gaz à effet de serre, d’une échelle d’étude fine à l’échelle de la parcelle en prairie permanente. L’efficacité du chaulage semble dépendre du type d’amendement et de son dosage et peut également interagir avec d’autres pratiques de gestion telles que la fertilisation azotée et le niveau d’intensité de gestion
The development of sustainable agriculture requires greater understanding of the impact of management practices on agroecosystem functioning, and on the ecosystem services provided by these agroecosystems. Representing nearly 68% of world's agricultural surfaces and contributing to the livelihoods of more than 800 million people, grasslands are one of the major agroecosystems where optimized agricultural practices are of concern. This PhD focuses on liming, a well-known practice for counteracting soil acidification (due to ongoing natural processes or accelerated by management practices), but which has variable efficiency in permanent grasslands. Indeed, liming effects on grassland are poorly documented and existing studies rarely take into account grassland multifunctionality. My thesis uses an integrated approach to improve the knowledge of liming impacts on grassland functioning. Different types of experiments – in the field (in situ), in semi-controlled conditions (mesocosms) and laboratory soil incubations (microcosms) – were used to study liming effects on different grassland compartments (vegetation, microorganisms, soil) along with possible interacting factors. Liming effectively increased soil pH in all the experiments. However, improving pH status did not always lead to greater forage production or increases in microbial and root biomass. My results showed that liming can enhance greenhouse gas emissions through several pathways (reemission of lime-derived carbon or stimulation of carbon mineralization), but may also reduce CO2 emissions from ecosystem respiration. Collectively, my findings emphasize the importance of pedoclimatic conditions for liming impacts on permanent grasslands and highlight the difficulty of upscaling liming effects, particularly on forage production and greenhouse gas emissions. The efficiency of liming appears to depend on the type and dose of soil improvers and can also interact with other management practices such as nitrogen fertilization and management intensification

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Brédoire, Félix. "Impacts of global change on the biogeochemical cycling of water and nutrients in the soil-plant system and consequences for vegetation growth in south-western Siberia". Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0033/document.

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Dans un contexte de changement global, prédire l’évolution de la productivité de la végétation dans le sud-ouest (SO) Sibérien reste un défi du fait d’incertitudes fortes sur les processus régulant la disponibilité en eau et en nutriments. Nous avons mis en évidence des relations entre cycles biogéochimiques, climat et propriétés du sol sur six sites contrastés.La croissance radiale des tiges de peuplier est principalement sensible au bilan hydrique du sol en forêt de steppe, au sud du SO Sibérien, alors qu’elle est stimulée par de hautes températures estivales en sub-taïga, dans le nord de la région.Des mesures de terrain et des simulations du bilan hydrique du sol ont montré que la fonte des neiges est importante pour la recharge des réserves hydriques du sol au sud. Au nord, ces réserves sont souvent rechargées en automne. La fonte des neiges est alors associée à du drainage. De plus, au nord, une épaisse couverture de neige protège le sol du gel en hiver. La distribution des racines fines est plus profonde en forêt de steppe qu’en sub-taïga, impactée par le déficit hydrique et le gel.L’homogénéité du statut en phosphore (P) des sols dans le SO Sibérien montre qu’il n’est pas encore très impacté par la pédogénèse. Les stocks en P élevés, notammen tles formes disponibles pour les plantes, suggèrent que le P n’est pas et ne sera pas limitant dans le futur.La décomposition des litières aériennes et la libération de l’azote (N) sont plus rapides en sub-taïga qu’en forêt de steppe. Un fort drainage pourrait expliquer un transfert profond du N dans les sols en sub-taïga. Cependant ces sols semblent efficaces pour retenir le N, limitant les pertes pour le système sol–plante
Predicting the evolution of vegetation productivity in SW Siberia in the contextof global change remains a challenge because of major uncertainties concerningthe biogeochemical cycling and the plant-availability of water and nutrients. Weprovided insights on their relation to climate and soil properties, investigating sixcontrasting sites.Aspen stem radial growth is mainly sensitive to soil water budget in the foreststeppezone established in the south of SW Siberia while it is enhanced by highsummer temperatures in the sub-taiga, in the north of the region.Field measurements and water budget simulations revealed that snow-melt isimportant re-filling soil water reserves in the south. In the north, these reservesare mostly re-filled in autumn and snow-melt is associated with drainage. A thicksnow-pack also prevents soil from freezing in winter in the sub-taiga. Water deficitand soil freezing largely impact the distribution of fine roots within the soil profilewhich is deeper in forest-steppe than in sub-taiga.The homogeneous soil phosphorus (P) status in the region investigated revealedthis nutrient has not been yet very impacted by contrasting soil processes. High Pstocks, and in particular plant-available forms, suggest P is unlikely to be limitingunder current and future conditions.By contrast, we found differences in nitrogen (N) status. Above-ground litterdecay and the release of N occurs faster in sub-taiga than in forest-steppe. Higherdrainage may explain deeper N transfer in sub-taiga soils. However, sub-taiga soilsalso seem to be efficient in retaining N, limiting losses from the soil–plant system

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Tonello, Victor Manoel Marques. "Principais aspectos do ciclo biogeoquímico do elemento carbono e seu contexto na atualidade". Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/91/91131/tde-15062007-110357/.

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O presente trabalho consistiu na produção de uma síntese sobre os principais aspectos do ciclo biogeoquímico do carbono, envolvendo aspectos recentes do efeito estufa na atmosfera, sendo também contextualizadas as políticas públicas e seus mecanismos sócio-econômicos; inserida num contexto atual, das mudanças climáticas, intimamente relacionadas à Convenção-Quadro das Nações Unidas sobre Mudança do Clima, Protocolo de Kyoto e Mecanismos de Desenvolvimento Limpo. Os ecossistemas terrestres prestam enorme contribuição de serviços ambientais ao homem na forma de oferta de água, alimentos e insumos gerais. Estes ganhos são sustentáveis na medida em que haja um equilíbrio estável entre a entrada e saída de certas variáveis. Ainda não se entende satisfatoriamente a funcionalidade dos ecossistemas naturais e sua plena interação com o clima, nas escalas local, regional e global; portanto, é uma responsabilidade social antecipar o entendimento dessa relação, antes que tudo se transforme. Não se sabe ao certo todas as conseqüências do aumento excessivo na temperatura terrestre, mas são esperadas alterações profundas em diversos ecossistemas, por exemplo: descongelamento das calotas polares e o conseqüente alagamento de regiões costeiras, alterações de intensidade e freqüência de chuvas, e alteração do metabolismo vegetal. São também previstas conseqüências na mudança das zonas climáticas e agrícolas e o desaparecimento de espécies sensíveis a esta mudança de temperatura. Procurando atingir o objetivo final da Convenção-Quadro das Nações Unidas sobre Mudança do Clima, em Kyoto – Japão, foi proposto o Protocolo de Kyoto, no sentido de possibilitar alcançar a estabilização das concentrações de gases de efeito estufa na atmosfera, num nível que não interfira perigosamente no sistema climático. Estabelece metas e prazos para controlar num primeiro esforço os principais gases de efeito estufa. Foram estabelecidos três mecanismos para auxiliar os países desenvolvidos no cumprimento de suas metas de redução ou limitação de emissões de gases de efeito estufa. Um desses mecanismos foi definido como Mecanismo de Desenvolvimento Limpo - MDL, sua implementação interessa particularmente aos países em desenvolvimento, pois permitirá a transferência de recursos e tecnologias para a redução de emissões. Neste contexto, exigi-se da classe cientifica respostas mais precisas e rápidas do entendimento de todos os processos envolvidos. O acompanhamento de projetos é importante, gerando informações para análises técnicas, científicas, sociais, ambientais e econômicas, que serão demandadas nas futuras negociações relativas à mitigação da mudança do clima.
The present work intends to present a synthesis of the information which is distributed in several areas. It approaches the main aspects of the global carbon cycle, including the recent greenhouse effect in the atmosphere, also including the political argumentation and the socioeconomic mechanisms associated. The work also brings a critical revision of the framework related to the United Nations Framework Convention on the Climate Change, the Kyoto Protocol and the Clean Development Mechanism. The terrestrial ecosystems provide enormous contribution of environmental services to the human beings in terms of water, foods, and general inputs supplies. The sustainability of this provision relies on the maintenance of the input/output equity of matter and energy throughout time. There is still no clear understanding of the natural ecosystems functioning and their interactions with climate in a broad perspective, from local to regional and global scales. Therefore it is a social responsibility to anticipate the understanding of this relation, before everything changes. The effects on the ecosystems of the temperature increase in the Earth surface are not fully understood, but strong changes are expected and some are already being measured in several ecosystems, for instance: mountain glaciers and the ice cap in the North Pole are declining, with foreseeable consequences of increasing sea level and flooding of coastal areas; changes in the cycle and intensity of rain events; changes in plant metabolism and distribution of agricultural species, interfering in food production and safety. The Kyoto Protocol was proposed aiming to achieve the objectives of the United Nations Framework Convention on the Climate Change, building the legal and political background for the Nations to lessen and stabilize the concentrations of greenhouse gases in the atmosphere. The Protocol established mechanisms for reduction and mitigation of greenhouse gases emissions including developed and developing countries. In terms of economical and technological gains, the Clean Development Mechanism – CDM, was one of the proposed mechanism of the Kyoto Protocol, which is particularly interesting to the developing countries. This mechanism allows resources and technologies transference for the reduction of GHG emissions in developing countries. In this context, the scientific community is an important component to bring more precise and fast answers to the understanding of all of the processes related to the actual influence of the Human kind in the planet.

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Jones, Auriane. "Effect of an engineer species on the diversity and functioning of benthic communities : the Sabellaria Alveolata reef habitat". Thesis, Brest, 2017. http://www.theses.fr/2017BRES0142/document.

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A travers le monde, les zones côtières abritent une grande diversité d’ingénieurs de l’écosystème accomplissant des fonctions clés comme le recyclage de la matière organique et des nutriments. Les habitats résultants de l’activité biologique de ces espèces sont exposés à de nombreuses perturbations comme la surpêche, le piétinement ou via l’aménagement des côtes. Dans ce contexte, il est urgent de comprendre le fonctionnement de ces habitats ingénieurés et comment ils sont affectés par des perturbations croissantes. Pendant ma thèse, j’ai utilisé l’habitat récifal construit par le polychète grégaire tubicole Sabellaria alveolata comme cas d’étude. Tout d’abord, les changements environnementaux et biotiques associés à la mise en place d’un récif à S. alveolata et à sa perturbation croissante ont été évalué, se concentrant sur les paramètres du sédiment (e.g. granulométrie, contenu en matière organique) ainsi que la diversité taxonomique et les assemblages d’espèces. De manière similaire, le troisième article se penche sur le fonctionnement trophique de la communauté récifale et d’une communauté contrôle afin de comprendre les effets de la mise en place de l’espèce ingénieur sur les transferts de carbone, s’intéressant successivement à l’ensemble de la communauté des consommateurs, aux consommateurs primaires et à l’importance des sources de nourriture autochtones (microphytobenthos et Ulva sp.) vs allochtone (phytoplancton). Dans cette partie, j’ai utilisé les isotopes stables du carbone et de l’azote ainsi que différentes approches analytiques telles que des mesures de la niche isotopique et des modèles de mélange. L’article 2 a pour but de comprendre les interactions entre complexité de l’habitat récifal, hétérogénéité des sources de nourriture autochtones et échelles spatiales dans l’explication des variations du rapport isotopique du carbone de S. alveolata et d’un suspensivore associée. Dans les deux derniers chapitres, j’ai traité la question du fonctionnement de l’habitat ingénieuré de manière directe, en utilisant des incubations de carottes benthiques pour mesurer des flux biogéochimiques (e.g. demande en oxygène), ou indirecte, en utilisant des indices de diversité fonctionnelle et isotopique intégratifs. Cette dernière partie révèle l’existence d’un optimum de densité de S. alveolata, utilisée comme proxy des perturbations, où la niche trophique et le fonctionnement biogéochimique du récif sont tous les deux maximaux
Coastal zones worldwide are home to a large diversity of ecosystem engineers that perform key functions such as the recycling of organic matter and nutrients. The habitats resulting from the biological activity of these species are exposed to numerous disturbances such as over harvesting and trampling or via coastal modification. In this context, it is becoming key to understand the functioning of these engineered habitats and how they are affected by increasing disturbances. During my PhD, I used the reef habitat built by the gregarious tubiculous polychaete Sabellaria alveolata as a study case. First, the environmental and biotic changes associated with the establishment of a S. alveolata reef and its increasing disturbance were assessed, focusing on sediment characteristics (e.g. grain-size distribution, organic matter content) along with taxonomic diversity and species assemblage. In the same vain, the third article looks into the trophic functioning of the reef community and a control community to understand the effects of the establishment of the engineer species on carbon transfers, successively looking at the whole consumer community, the primary consumers and the importance of autochthonous (microphytobenthos and Ulva sp.) vs allochthone (phytoplankton) food sources. In this part, I used carbon and nitrogen stable isotopes and different analytical approaches such as isotopic niche metrics and mixing models. Article 2 aims towards understanding the interactions between reef habitat complexity, autochthonous food source heterogeneity and spatial scales in explaining the carbon isotopic ratio variations of S. alveolata and an associated suspension-feeder. In the last two chapters, I address the functioning of the engineered habitat either directly, using benthic core incubations to measure biogeochemical fluxes (e.g. oxygen demand) or indirectly, through the use of integrative functional and isotopic diversity indices. This last part reveals the existence of an optimum value of S. alveolata density, used as a disturbance proxy, where the trophic niche and the biogeochemical functioning of the reef are both maximal

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Askri, Amira. "Valorisation des digestats de méthanisation en agriculture : effets sur les cycles biogéochimiques du carbone et de l'azote". Thesis, Paris, AgroParisTech, 2015. http://www.theses.fr/2015AGPT0023.

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La digestion anaérobie est un mode de traitement biologique des déchets organiques qui se développe fortement en France. En plus de produire de l‟énergie, le digestat issu du procédé a des caractéristiques qui devraient lui conférer un potentiel agronomique intéressant. L‟objectif de ce travail était d‟étudier l‟effet d‟apport au sol de digestats de méthanisation sur les cycles biogéochimiques du C et du N, en particulier leur potentiel de stockage de C dans les sols et la disponibilité potentielle du N pour les plantes, ainsi que sur les émissions de N2O associées à leur apport. L‟accent a été mis sur la variation de ces effets avec le type de déchets entrants en digestion et les post-traitements subis après la digestion. Ces travaux ont reposé sur des expérimentations en laboratoire, un essai de courte durée au champ et la modélisation.Cinq types de digestat ont été utilisés, trois d‟origine agricole et deux issus du traitement de déchets urbains issus ou non de collecte sélective. Quatre digestats bruts sont issus de méthanisation par voie humide et subissent une séparation de phase produisant deux digestats : liquide et solide. Le dernier digestat est issu de méthanisation par voie sèche. Les deux digestats solides d‟origine urbaine subissent ensuite un compostage. Par ailleurs le séchage et l‟osmose inverse ont été testés sur 2 des filières agricoles.Les digestats d‟origine agricole ont les pouvoirs fertilisant et amendant les plus importants. Le post-traitement par séparation de phase permet de distinguer un produit solide destiné à entretenir les stocks de C du sol qui peut être amélioré encore par le compostage et un produit liquide qui a un pouvoir fertilisant plus important. Les digestats bruts, solides et liquides sont tous caractérisés par une fraction résiduelle de C facilement biodégradable variant de 23 à 91% de leur carbone, associée au C de la fraction extractible à l‟eau chaude des digestats. La stabilité du C des digestats augmente dans l‟ordre liquide18%, solides et compostés ont un caractère amendant intéressant. Les digestats de méthanisation ont un fort pouvoir fertilisant azoté, essentiellement lié à la fraction de N ammoniacal présente initialement dans les digestats. Les C/N organiques relativement élevés génèrent des tendances à l‟organisation du N associées à la dégradation de la MO résiduelle des digestats.Un jeu de paramètres homogènes a pu être déterminé pour simuler avec le modèle CANTIS les cinétiques de minéralisation de C et de N après apport des digestats. Ce jeu de paramètres homogènes permet au modèle CANTIS de valider les relations entre le maintien du stock de C, la valeur fertilisante des digestats et leurs propriétés biochimiques.Les digestats bruts sont ceux pour lesquels les émissions de N2O après apport sont les plus fortes. Les post-traitements par séparation de phase et compostage diminuent ces émissions, les post-traitements par séchage ou osmose inverse les accentuent montrant la difficulté à associer intérêt agronomique maximal et absence d‟impacts environnementaux.Au champ, une forte perte d‟azote minéral est constatée après apport des digestats, sans doute liée à la volatilisation de l‟azote ammoniacal. Les digestats non compostés présentent des coefficients équivalent engrais compris entre 0.37 et 0.52 sans qu‟on ait pu mettre en évidence d‟effet de l‟origine des déchets traités et de la séparation de phase. En revanche le compostage diminue de plus de 80% l‟équivalence à l‟engrais azoté
Anaerobic digestion is a biological treatment of organic wastes which is strongly developing in France. In addition to producing energy, anaerobic digestion produces a digestate that has interesting agronomic potential. The objective of this work was thus to study the effect of applying digestates to a soil on the biogeochemical cycles of C and N, particularly the C storage potential in soil and the availability of N for plants, as well as the N2O emissions. The variation of these effects with the type of digested inputs and with the post-treatments after digestion was also studied. These studies were based on laboratory experiments, a short-term field experiment and modeling.Five types of digestates were used: three of agricultural origin and two from urban wastes coming from separate collection or not. Four raw digestates were produced by wet anaerobic digestion and underwent phase separation producing thus two digestates: liquid and solid. The other digestate was produced by dry anaerobic digestion. The solid digestates from urban origin underwent composting also while the two digestates of agricultural origin underwent reverse osmosis and drying.The digestates produced from agricultural wastes have the higher fertilizer and amending potentials. The phase separation produced a solid product which can mostly be used to maintain soil C stocks and which can be further improved by composting and a liquid product that has a greater fertilizing potential. All digestates raw, solid and liquid are characterized by a residual fraction of readily biodegradable C ranging from 23 to 91% of their organic C and related to the C content of the hot water extractable fraction. The biological stability of the digestates increases in this order: liquid 18%, the solid and the composted digestates have an interesting amending potential. The anaerobic digestates have also a high nitrogen fertilizer value, mainly related to the fraction of ammonia N initially present in the digestate; nevertheless, the high organic C/N ratios generate relatively high nitrogen organization associated with the degradation ofdigestate organic matter.A unique set of parameters was determined from the previous experimentations to simulate the C and N mineralization kinetics, after applying digestates to the soil, using the CANTIS model. This set of parameters was used to evaluate the relationship between the soil C stock and the fertilizer value of digestate and their biochemical properties.N2O emissions are higher from the raw digestates; but post-treatment by phase separation and composting reduce these emissions, while reverse osmosis and drying increase them showing thus the difficulty in associating agronomic interest and lack of environmental impacts at the same time.In the field, a high loss of mineral nitrogen is found after application of digestate, probably because of the volatilization of ammonia nitrogen. The non-composted digestates have fertilizer equivalence between 0.37 and 0.52; the origin of the digestate and phase separation didn‟t have effect on this parameter. On the other side, composting decreases by more than 80% the equivalence to nitrogen fertilizer

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Demestihas, Constance. "Analyse des conflits et synergies entre services écosystémiques multiples en vergers de pommiers". Thesis, Avignon, 2017. http://www.theses.fr/2017AVIG0690/document.

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Le concept de « service écosystémique », en plein essor depuis la publication du Millenium Ecosystem Assessment en 2005, a permis de souligner l'importance des performances non-marchandes des écosystèmes. En arboriculture, assurer une bonne productivité tout en préservant les ressources naturelles et la santé humaine est aujourd’hui un défi majeur, qui peut être analysé sous l’angle des services écosystémiques. Quels sont ces services au sein d’un verger de pommiers ? Comment les analyser ? Quels sont les liens - conflits et synergies - entre services écosystémiques multiples et comment les systèmes de culture modifient-ils les profils de services multiples? Ce travail de thèse vise à répondre à ces questions avec une démarche novatrice combinant mesures expérimentales, modélisation et analyse statistique. Suite à une analyse bibliographique des services écosystémiques pouvant être délivrés dans des vergers, cinq services ont été sélectionnés. Il s’agit de la production de fruits, de la disponibilité de l’azote dans le sol, de la régulation du climat reposant sur la prévention de la dénitrification de l’azote et sur la séquestration du carbone, de la maintenance et de la régulation du cycle de l’eau y compris de sa qualité, et de la régulation des bioagresseurs. Conjointement à ces services nous avons considéré les nuisances environnementales dues aux pesticides. Pour chaque service nous avons identifié les fonctions écosystémiques sous-jacentes ainsi que les pratiques agricoles et les conditions pédoclimatiques ayant un impact sur ces fonctions. Les services et fonctions ont été décrits par un ou plusieurs indicateurs et quantifiés à l’aide de modèles dans les cas suivants : (i) neuf systèmes de culture réels sur deux dispositifs expérimentaux dans le sud-est de la France et (ii) 150 systèmes de culture fictifs conçus à partir de la combinaison de cinq leviers de pratiques et de leurs modalités, dans des conditions pédoclimatiques identiques. Les deux modèles utilisés ont été STICS, un modèle générique de simulation du fonctionnement du sol et des cultures sous l’influence des pratiques, qui a nécessité une paramétrisation et une évaluation sur pommier à partir de mesures expérimentales, et IPSIM, une plateforme de modélisation simulant les effets des pratiques et des conditions du milieu sur les dégâts aux cultures causés par les bioagresseurs. IPSIM a été paramétré sur pommier, sur la base d’une importante étude bibliographique et à dires d’experts. Les simulations des modèles ont fait l’objet d’analyses statistiques simples dans le cas des systèmes de culture réels, et d’analyses multivariées à deux tableaux (analyse en composantes principales avec variables instrumentales) pour les systèmes de culture fictifs. Pour les neufs systèmes de culture réels, 14 liens importants entre services écosystémiques ont été identifiés, notamment des conflits comme celui entre la prévention de la dénitrification ou de la lixiviation de l’azote et la disponibilité de l’azote dans le sol à court terme, et des synergies, comme celle entre l’humidité du sol ou la séquestration du carbone et la disponibilité de l’azote dans le sol à court terme. Ces liens entre services sont expliqués par les fonctions écosystémiques sous-jacentes. La comparaison de profils de services entre systèmes a mis en évidence l’impact de pratiques agricoles sur certains services. Ainsi, sur un même site, une forte densité de plantation augmente la production de fruits et la séquestration du carbone. La fertilisation exclusivement sous une forme organique diminue la production de fruits via un stress azoté mais diminue également la lixiviation. Par ailleurs, les profils de services sont fortement influencés par les caractéristiques pédoclimatiques de chaque site. Ces résultats confortent la nécessité d’une prise en compte explicite de l’interdépendance ‘pratiques x conditions du milieu’ pour analyser les services
The concept of « ecosystem service », which has been used increasingly since the publication of the Millennium Ecosystem Assessment in 2005, has highlighted the importance of ecosystem’s non-marketed performances. In orchards, ensuring high productivity while preserving natural resources and human health has become a real challenge that could be analyzed with the concept of ecosystem service. Which ecosystem services are delivered in an apple orchard? How to analyze them? What are the relationships - conflicts or synergies – among multiple ecosystem services and how do cropping systems change multiple ecosystem service profiles? This PhD work aims at answering those questions with an innovative approach combining experimental measures, modeling and statistical analysis.Based on a literature review of ecosystem services in orchards, five services were selected: fruit production, nitrogen availability in soil, climate regulation based on the prevention of nitrogen denitrification and on carbon sequestration, maintenance and regulation of water cycle, including water quality, and pest control. We also considered the environmental disturbances caused by the use of pesticides. For each service, we identified the underlying ecosystem functions as well as the agricultural practices and soil and climate conditions affecting these functions. Services and functions were described by one or multiple indicators and quantified using models in the case of (i) nine existing cropping systems on two experimental sites in southeastern France differing in terms of soil and climate conditions, and (ii) 150 virtual cropping systems designed out of the combination of five major agricultural practice levers and their modalities, in identical soil and climate conditions. The two models used were STICS, a generic soil-crop simulation model under the influence of practices which required a parameterization and an evaluation on apple orchards based on experimental measures, and IPSIM, a generic modeling framework simulating the impacts of agricultural practices and local conditions on crop injuries caused by pests. IPSIM was parameterized on apple orchards, based on an important literature review and expert opinions. Model simulations were analyzed with simple statistics in the case of the nine existing cropping systems and with two-table multivariate analyses (principal component analysis with instrumental variables) for virtual cropping systems.Concerning the existing cropping systems, 14 important relationships were identified among ecosystem services, especially conflicts, like the one between nitrogen denitrification or leaching prevention and soil nitrogen availability on the short term, and synergies such as the one between soil humidity or carbon sequestration and nitrogen availability on the short term. These relationships are explained by the underlying ecosystem functions. Comparing service profiles among cropping systems highlighted the impacts of agricultural practices on some services. That way, on a same site, a high planting density increases fruit production and carbon sequestration. An exclusively organic fertilization decreases fruit production through nitrogen stress but also nitrogen leaching in drained water. Furthermore, service profiles are strongly influenced by the soil and climate conditions of each site. These results strengthen the need to explicitly consider the ‘agricultural practices x soil and climate conditions’ interdependence in order to analyze ecosystem services. The results obtained with the virtual cropping systems simulations confirmed those of the existing ones and gave precision on the impacts of fertilization, irrigation and pest control for codling moth, rosy apple aphid and apple scab on ecosystem functions and services

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38

Minaudo, Camille. "Analyse et modélisation de l'eutrophisation de la Loire". Thesis, Tours, 2015. http://www.theses.fr/2015TOUR4047/document.

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Ce travail a pour objectif d’étudier les conditions physicochimiques qui causent dans la Loire des développements excessifs de phytoplancton, et de mettre en évidence les modifications des équilibres biogéochimiques qui en résultent. L’analyse des variables de l’eutrophisation a été conduite sur plusieurs niveaux d’échelle temporelle et spatiale, sur la base de longues chroniques de qualité de l’eau (1980- 2012), de données acquises à l’échelle journalière pendant la thèse (2012-2014), et d’un modèle numérique biogéochimique à résolution horaire. Depuis les conditions hypereutrophes des années 1980, la biomasse phytoplanctonique qui se développe en période estivale a été réduite d’un facteur 2,5 dans la Loire et dans ses affluents, de manière concomitante avec la baisse généralisée d’un facteur 3 des teneurs en phosphore biodisponible, liée au contrôle des rejets ponctuels urbains et industriels. Le fleuve de la Loire (France) reste cependant sensible à l’eutrophisation, du fait d’une forte pression agricole et urbaine, des étiages prononcés, et une morphologie fluviale à chenaux multiples qui ralentit l’écoulement, laissant pleinement au phytoplancton le temps de se développer. Lorsque les conditions hydrologiques le permettent, le développement du phytoplancton impacte fortement le fonctionnement de l’écosystème, en agissant significativement sur les cycles biogéochimiques des nutriments, du carbone et de l’oxygène
This thesis aims at studying the physical and chemical causes and consequences that result from excessive phytoplankton growth in the Loire River. The analysis identified some parameters characterizing river eutrophication and was conducted on several spatial and temporal scales. This was based on long-term water quality time-series (1980-2012), a daily survey carried out during this work (2012-2014), and the numerical modeling of the river biogeochemical functioning with an hourly resolution. Phytoplankton development in summer was reduced 2.5-fold in the Loire River and in the main tributaries, synchronously with the generalized reduction 3-fold of bioavailable phosphorus as a result of controlling and limiting phosphorus point sources. However, the Loire River remains sensitive to eutrophication, with a significant urban and agricultural pressure, low water levels in summer, and its multiple channels morphology slowing down the water velocity. All these factors combined favor phytoplankton development. When hydrological conditions are favorable, phytoplankton grows and significantly affects the ecosystem functioning, with an impact on nutrients, carbon and oxygen biogeochemical cycles

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39

McAndrew, Patricia M. "Effects of nutrient enrichment and mesoscale eddies on metabolic balance in the subtropical North Pacific Ocean". Thesis, 2006. http://hdl.handle.net/10125/20802.

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40

Costello, David M. "Effects of invasive species and chemical contaminants on biogeochemical fluxes across ecosystem boundaries". 2009. http://etd.nd.edu/ETD-db/theses/available/etd-12032009-104607/.

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41

Cai, Meijun. "Long-term Acid Deposition Effects on Soil and Water Chemistry in the Noland Divide Watershed, Great Smoky Mountains National Park, USA". 2010. http://trace.tennessee.edu/utk_graddiss/680.

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Impacts of long-term acid deposition on soil and water chemistry are of particular concern in the Great Smoky Mountains National Park (GRSM), receiving some of the highest acid deposition rates in the eastern United States and limited by inadequate acid buffering capacity. In the GRSM, the Noland Divide watershed (NDW) has been monitored since 1991 for water chemistries of precipitation, throughfall, soil, and stream. The impacts of long-term acidic deposition on stream water quality in the NDW were investigated through: 1) development of an ion input-output budget; 2) analysis of trends and seasonal patterns for major ions; 3) comparison of net export rates between baseflow and stormflow periods; and 4) characterization of soil chemistry and transport properties for various potential acid deposition scenarios. Between 1991 and 2006, throughfall deposition remained unchanged and consisted of 1,735 eq ha-1 yr-1 of SO42-, 863 eq ha-1 yr-1 of NO3-, and 284 eq ha-1 yr-1 of NH4+. Net retention of sulfate was estimated at 61% being controlled by soil adsorption, and inorganic nitrogen was retained at 32% presumably due to plant uptake. Nitrogen retention increased by 44.30 eq ha-1 yr-1 over the study period. Besides deposition, soil acidity was increased by nitrification and precipitation-driven desorption of previously accumulated sulfate. To neutralize soil acidity, Ca2+, Mg2+ and Na+ were depleted from NDW by 77, 46 and 66 eq ha-1 yr-1, respectively. Due to the continuous addition of acidity, base saturation in soil was reduced to 4% at present. Mobilization of aluminum and other metals (Mn and Zn) may be enhanced by these geochemical processes, potentially causing toxic conditions to fish and other biota in the GRSM streams. Impacts of acidic deposition on streams were confirmed by measured stream pH below 6 and acid neutralizing capacity below 0.01 meq L-1. During stormflows pH and ANC depressions occurred primarily due to increases in sulfate transport, leading to episodic acidification events. This study provides new information on hydrological and biogeochemical processes that regulate stream acidification events in the southern Appalachian region, supporting improved management strategies for GRSM streams.

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42

Ashagrie, Yeshanew [Verfasser]. "Effects of land-use changes on the properties of a nitisol and hydrological and biogeochemical processes in different forest ecosystems at Munesa, south-eastern Ethiopia / vorgelegt von Yeshanew Ashagrie". 2005. http://d-nb.info/975444093/34.

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43

Kao, Kai-Jung, e 高愷嶸. "Effect of Typhoon Saola on biogeochemical responses in the subtropical oligotrophic northwestern Pacific ocean". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/01912476133870691171.

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碩士
國立臺灣海洋大學
海洋環境化學與生態研究所
102
Abstract Global warming will increase the frequency of extreme weather, especially in the marine biogeochemical cycle. Therefore, global warming is definitely an important topic in the global change research field. The oligotrophic northwestern Pacific ocean appears to be a nitrogen-limited system, also typhoons occur frequently in this area. Because of hard to get the in situ data. So this study utilized two cruises to get in situ data before, and after Typhoon Soala passes (during 26 July to 6 August 2012). We conducted our research from eastern Taiwan to 124 oE. In this area, we set nine long-term observation sampling stations 15 nm apart. Our study result shows that after typhoon, mixed layer depth deepened from 23±6 m to 45±11 m (approximately 99%), and sea surface chlorophyll a concentration increased from 0.15±0.03 mg m-3 to 0.21±0.03 mg m-3. Since the study area was an oligotrophic ocean, chlorophyll was highly concentrated in the subsurface of the ocean. Typhoon enhanced ocean vertical mixing, which increased sea surface chlorophyll a concentration. After typhoon, integrate chlorophyll a concentration significant increased form 29.6±3.4 mg m-2 to34.5±6.0 mg m-2(P<0.05). Furthermore, chlorophyll a concentration increased at subsurface and chlorophyll max depth became shallow from chlorophyll a profile. That is because of nitracline depth shallower than others stations before typhoon. Since the intense wind of typhoon can induce strong ocean mixing, deeper-ocean nutrient could be brought to the euphotic zone and increase in phytoplankton biomass(4.96±3.64 mg m-2). And the Stations are 60% controlled by cold eddy. After typhoon, primary production decreased from 265±91 mgC m-2 d-1to 229±46 mgC m-2 d-1. Since the primary productivity decreased, we speculated that phytoplankton does not suit the environment yet. So primary production cannot be increased with phytoplankton biomass. Previous studies of typhoon induced phytoplankton bloom are largely based on satellite remote sensing data. And based on our data, the increase of sea surface chlorophyll a concentration should result in a higher primary production. But in our study result, we cannot get the same outcome as other's model-based productivity calculation. It is necessary to adjust other's model-based calculation and research approach.

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44

Yeh, Tzu-ying, e 葉子嫈. "The effect of tidal action on the biogeochemical process and the primary production in the East China Sea". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/73209490216833484301.

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碩士
國立中央大學
水文與海洋科學研究所
99
Abstract A coupled physical-biogeochemical model has been used to simulate the distributions of nutrient(i.e. DIN, dissolved inorganic nitrogen) and chlorophyll(Chl-a) in the East China Sea and to predict primary productivity(Liu et al.,2010). Concentrations of DIN, Chl-a and the integrated primary production(IPP) are similar to observations of Gong et al.(2003). However, the model relies on nudging towards observed climatological distribution DIN. Without nudging, the modeled DIN is much higher than observations near the Changjiang river mouth and much lower than observations in most of the far field. The mostly underestimated DIN causes underestimating Chl-a and PP. The high values in the near field result from the high DIN concentration of the ChangJiang run off prescribed for the model. Since Changjiang estuary is an estuary of medium tidal range, its tidal action can influence the dispersal of Changjiang plume. In this study, we add the tidal action in the ECSmodel to explore how tidal action influences the biochemistry of the East China Sea and compare the output with observations. The tidal action is incorporated in the model by prescribing the sea level changes caused by tides on the open boundaries, so that the tidal actions may propogate into the model domain. The tidal action makes the Changjiang plume more dispersive and better resembling observations. In addition, it induces stronger horizontal and vertical mixing so that the distribution of DIN concentration in the surface layer close to the observations. On the other hand, the total DIN in the upper 60m remains nearby the same, indicating the tidal action merely moves. DIN from the subsurface layer to the surface layer, which enhances photosynthesis. The additional concentration of DIN in the surface layer increases the IPP by 40% on an annual basis. The modeled annual mean IPP reaches 93% of the observated mean value. For the water depth of 0 ~ 30m, the mean concentration of modeled DIN increases from 1 ?m to 2 ?m in the ECS shelf region by tidal action. From Michaelis-Menten kinetics, the phytoplankton growth rate can reach 91% of maximam phytoplankton growth rate, which may explain the enhanced primary productivity.

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