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1
Murray, Sam. « Development of a soil respiration isotopic sampling system ». Thesis, University of Canterbury. School of Biological Sciences, 2014. http://hdl.handle.net/10092/9652.
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The rate of carbon turnover in soil is a balance between the input of carbon by plants through their roots and associated fungi and the loss of carbon due to plant and microbial respiration, oxidation and leaching. Soil carbon dynamics are notoriously difficult to measure, and being able to separate total soil respiration into its autotrophic and heterotrophic components would help understanding of carbon cycling processes. Where autotrophic respiration originates from roots and their associated mycorrhizal fungi, using newly fixed carbon, and heterotrophic respiration originates from the breakdown of older soil organic matter.
By calculating the δ¹³C signature of respired CO₂ (the ratio of the abundances of C isotopes ¹²C and ¹³C) it is possible to determine whether it is of heterotrophic or autotrophic origin. In this study a 6 chamber, constant CO₂ concentration measuring apparatus was developed to determine both the rate of CO₂ efflux and to collect undisturbed CO₂ samples for isotope analysis. This apparatus was tested using live soil samples with different δ¹³C values (-22 ‰ to -27 ‰) and respiration rates (2 – 8 µmol m⁻² s⁻¹) obtained from various locations in New Zealand. Testing involved taking samples using the respiration apparatus, then incubating the same samples in a bag, and then comparing the two. There was no difference between the results from the soil respiration apparatus and the bags (R²=0.96, p=0.0002).
Twelve microcosms including soil and grass were extracted from a newly converted dairy farm and placed into in growth cabinets. Diurnal courses of partitioned soil respiration were made over 24 hours with constant soil temperature to eliminate temperatures effect on soil respiration. Half were then covered with 90% shade cloth for 12 days to test if a reduction in light (and therefore newly fixed carbon) would have any effect on soil respiration. There was a significant reduction in soil respiration, yet no detectable change in the δ¹³C of soil respired CO₂ under heavily shaded treatment. There was however there was a shift towards heterotrophic dominated respiration. This shows that while L. perenne is resilient to surrounding conditions it is susceptible to change if exposed to different conditions for prolonged periods of time. The use of this new technique in the field will allow improved understanding of factors effecting soil C efflux.
2
Rühr, Nadine Katrin. « Soil respiration in a mixed mountain forest : environmental drivers and partitioning of component fluxes / ». [S.l.] : [s.n.], 2009. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=18297.
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Heim, Brett Christopher. « Partitioning soil respiration in response to drought and fertilization in loblolly pine : laboratory and field approaches ». Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/25757.
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An understanding of ecosystem-level carbon (C) sequestration, or net ecosystem production (NEP), requires the separation of heterotrophic, microbial respiration (RH) from autotrophic, root-derived respiration (RA) as the components of RS (i.e., NEP = NPP - RH). However, separating these two sources in situ has been problematic since they are closely coupled. This study utilizes two similarly aged Pinus taeda L. stands, 8 and 9 years-old, aimed at quantifying these two respiration components through in-situ root severing. In order to use root-severing treatments to separate RS into RH and RA components, confirmation of carbohydrate depletion coupled to RA decline is crucial. This study evaluated the changes in CO2 flux rates and carbohydrate supply upon root severing in Pinus taeda L. using a controlled laboratory validating a two-part field study. The first field study used root-severing cores to test in-situ if respiration components can be attained based on the depletion of carbohydrate supply. The second field study was aimed at how future changes in climate might affect the ability of forests to store C and how modern forestry practices might affect changes and was conducted over the course of two installations, spring and summer 2012. In this study we examined the effects of fertilization (0 and 100.9 kg N ha-1 ) and throughfall reduction (0 and -30%) on total soil respiration (RS) as well as the heterotrophic contribution to RS, in a fully replicated (n=4), 2x2 factorial design. In the controlled lab experiment RS and RA declined by 86% and 95% respectively by the end of an 86 day trial and NSC carbohydrates declined by 60% for soluble, 29% for insoluble, and 43% for total (soluble + insoluble). The decline of RA was highly correlated to with the decline of NSC’s at 0.90, 0.69 and 0.93 for soluble, insoluble and total, respectively. The companion field study revealed a mean decrease 21±0.5% of over the final three dates when severed root respiration stabilized. In the second study, testing throughfall reduction and fertilization levels there were no fertilization by throughfall reduction interactions on the contribution of RH to RS in either the spring or summer; however, the main effect of throughfall reduction was significant in the spring. During the spring, the mean contribution of RH to RS for ambient throughfall plots was 96±6.4%, while the mean contribution under throughfall reduction was 68±1.9%. During the summer, there were no differences among treatments and the overall contribution of RH to RS was 78±1.6%. Collectively, both of these studies revealed that the severing of roots from their primary energy source and the subsequent depletion of stored NSC that the use of in-situ methods allows for the quantification of soil respiration components RA and RH. Using these estimates to model NEP in the short-term can be variable by season, however, long-term monitoring may simplify future NEP modeling scenariosMaster of Science
4
Nottingham, Andrew Thomas. « The carbon balance of tropical forest soils : partitioning sources of respiration ». Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608423.
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FERRE', CHIARA. « Monitoring of greenhouse gas emissions from agricultural and forest soils ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2009. http://hdl.handle.net/10281/7483.
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Global climate change is becoming a central issue in contemporary science as well as politics. There is a long-lasting debate about the cause of the climate change: anthropogenic activity versus the natural cycle. However, a scientific consensus is coming a conclusion that the contemporary climate change is mainly caused by anthropogenic emissions of the greenhouse gases (GHG), including carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4).
The main objective of the thesis is the monitoring of such GHG emissions from two ecosystem types: a forest and a rice paddy ecosystem. The forest site is a EMEP experimental station, taking part of the activity of GHG-AGOLU of FP7-JRC project, while the agricultural ecosystem was included in the CarboEurope project and represents also a Level 3 site in the frame of NitroEurope project. The gas monitoring was carried out in 2008.
The thesis is composed by 4 chapters, corresponding to specific objectives. The first chapter is relative to the study of the spatial variability of the main soil chemical and physical properties on the basis of which the gas monitoring points were selected. The second and the third chapters are relative to a cropland site. In particular, the second chapter includes monitoring data of CH4, N2O and CO2 fluxes from the paddy field, both during the crop growth season and the fallow period, and the validation results of the DeNitrification DeComposition (DNDC) model, a process-oriented biogeochemical model used for simulating soil gas emissions from the paddy field, are reported. The third chapter contains the study of characterization of microbial community composition using phospholipid fatty acid analysis (PLFA), at eight sampling dates representative of different soil conditions and crop stages and consequently characterized by distinct soil greenhouse emission rates.
The fourth and last chapter includes the monitoring study of soil respiration in a forest site and its partitioning into autotrophic and heterotrophic components, applying the indirect linear regression method.
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Deliberali, Isabel. « Captura e alocação de carbono em Pinus taeda e Pinus caribaea var. hondurensis sob manejos hídricos e nutricionais distintos ». Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/11/11150/tde-09032016-112849/.
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O gênero Pinus ocupa no Brasil uma área plantada de 1,59 milhão de hectares e tem uma ampla faixa de produtividade florestal (18 a 45 m3 ha-1 ano-1), em função das espécies utilizadas, das limitações edáficas, dos tipos de clima, melhoramento genético e, e alguns casos, pela ocorrência de pragas e doenças. Apesar do conhecimento de que o aumento da disponibilidade de recursos naturais (luz, água e nutrientes) eleva a produção de madeira, faz-se necessário compreender como estes recursos influenciam os processos de captura (produção primária bruta ou GPP) e alocação de carbono (C) para os diferentes compartimentos da floresta (raiz, lenho, galhos e folhas). Além disso, o grau de controle genético é de grande importância nesses processos e também deve ser analisado. Assim, este projeto objetivou quantificar as taxas de captura e alocação de carbono em uma espécie de Pinus tropical (P. caribaea var. hondurensis) e em uma subtropical (P. taeda), dos 6,5 aos 8,5 anos de idade, em parcelas controle (sem fertilização e sem irrigação) e parcelas fertilizadas e irrigadas. O experimento está localizado no município de Itatinga - SP e se utilizou o método do balanço de carbono para estimar a produtividade primária líquida da parte aérea (ANPP), o fluxo de carbono para o solo (TBCF), produtividade primária bruta (GPP) e produtividade líquida do ecossistema (NEP). Ao final do estudo, a biomassa do tronco foi 75% superior no P. caribaea var. hondurensis (126 Mg ha-1) do que no P. taeda (72 Mg ha-1), sendo que em ambas as espécies houveram ganhos significativos com a fertilização e irrigação. O primeiro ano avaliado foi mais seco do que o segundo (1195 contra 1487 mm), resultando em diferenças nos fluxos calculados. A produção de tronco do P. caribaea var. hondurensis variou de 722 a 1569 gC m-2 ano-1, enquanto do P. taeda foi de 221 a 452 gC m-2 ano-1. A espécie subtropical obteve os maiores valores de TBCF, variando de 1150 a 2197 gC m-2 ano-1, e para as duas espécies se encontrou relação do TBCF com a ANPP e GPP. Assim, encontrou-se que a maior produtividade da espécie tropical é resultado de seu maior GPP (4964 contra 3744 gC m-2 ano-1 no P. taeda), maior partição de carbono para incremento de tronco (22% contra 9% no P. taeda) e menor partição para TBCF (23% contra 45% no P. taeda). Já a fertilização e irrigação não mudaram a partição da GPP para a ANPP e TBCF comparado ao tratamento controle, e o ganho em produção de madeira foi explicado apenas pelo aumento na GPP (11%). A NEP para ambas as espécies foi positiva, mostrando que essas espécies estão atuando como drenos de carbono. Assim, o conhecimento de como a captura e alocação de C é afetada pela espécie, água e nutrição terá aplicação sobre o manejo florestal, além de propiciar valores de fluxos essenciais para a calibração de modelos ecofisiológicos de produção, ainda inexistentes para essas espécies no Brasil.The genus Pinus in Brazil has a planted area of 1.59 million hectares and it has a wide range of forest productivity (18-45 m3 ha-1 yr-1) depending on the species, edaphic limitations, climate, breeding and, in some cases, the occurrence of pests and diseases. Despite knowing that the increased resources availability (light, water and nutrients) improves the production of wood, it is necessary to understand how these features influence the uptake processes (gross primary production or GPP) and carbon allocation (C) on the different forest compartments (root, bole, branch and leaf). Furthermore, the degree of genetic control is rather important in these processes and should also be analyzed. Thus, this project aimed to quantify carbon sequestration and allocation rates in a tropical pine (P. caribaea var. hondurensis) and a subtropical one (P. taeda), from ages 6.5 to 8.5 years old, in control plots (no fertilization and no irrigation) and fertilized and irrigated plots. The experimental site is located in Itatinga- SP and the carbon balance approach was used to estimate the above ground net primary production (ANPP), total belowground carbon flux (TBCF), gross primary production (GPP) and net ecosystem production (NEP). At the end of the study, the bole biomass was 75% higher in the P. caribaea var. hondurensis (126 Mg ha-1) than in P. taeda (72 Mg ha-1), and in both species there were substantial improvements with fertilization and irrigation. The first year evaluated was drier than the second (from 1195 to 1487 mm), resulting in differences in the calculated fluxes. The P. caribaea var. hondurensis bole production ranged from 722 to 1569 gC m-2 yr- 1, while the P. taeda showed values from 221 to 452 gC m-2 yr-1. The subtropical specie obtained the largest values of TBCF (from 1150 to 2197 gC m-2 yr-1), and on both species there was relationship between TBCF and ANPP and GPP.Thus, the higher productivity of tropical specie is a result of higher GPP (4964 versus 3744 gC m-2 yr-1 in the P. taeda), increased carbon partitioning to bole increment (22% versus 9% in the P. taeda) and smaller partitioning for TBCF (23% versus 45% in the P. taeda). Fertilization and irrigation have not changed the partitioning from GPP to ANPP and TBCF compared to the control plots, and increase in the production of wood it has been explained only by increased GPP (11%). The NEP for both species was positive, showing that these species are acting as carbon sinks. Therefore, the knowledge of how the carbon sequestration and allocation is affected by the species, water and nutrition will have application on forest management, besides providing values of essential fluxes for calibration of ecophysiological production models, still non-existent for these species in Brazil.
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Stewart, Heather 1971. « Partitioning belowground respiration in a northern peatland ». Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=98806.
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To further the understanding of respiration processes of northern peatlands, the relative importance of each type of belowground respiration was determined at Mer Bleue, a northern peatland located near Ottawa, Ontario, from June to November, 2003. Direct measurements of total, soil organic matter (SOM) and root respiration were made, with rhizosphere respiration determined by residual. Although an aboveground source, determination of live Sphagnum respiration was also attempted in the field. To identify changes in CO2 fluxes with environmental conditions, peat temperature and water table levels were monitored throughout the study period.SOM respiration was higher than hypothesized at 63% while root and rhizosphere respiration were lower than hypothesized at 21% and 16%, respectively, of total belowground respiration. As the field experiment for determining live Sphagnum respiration was unsuccessful, it was determined by calculation to be 18% of total respiration, slightly higher than hypothesized. Opposite of hypothesized, air temperatures, peat temperatures and water table levels generally had weak and insignificant relationships when linearly regressed with total respiration.
8
Zia, Afia. « Soil-solution partitioning of metals ». Thesis, University of York, 2012. http://etheses.whiterose.ac.uk/3163/.
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ABSTRACT Soil- solution partitioning of metals determines the behaviour and toxicity of metals. Lead, copper, zinc and nickel are common pollutants, and due to historic metal deposition from the atmosphere, high levels of these metals have accumulated in upland organic soils in the UK. Atmospheric deposition of sulphur and nitrogen, and climate change, can affect soil solution pH and dissolved organic carbon (DOC) concentrations, and both pH and DOC are known to affect soil-solution partitioning of metals. In this thesis, metal concentrations were determined in archived soil and soil solution samples from a regional survey of upland sites in northern England with contrasting soils, and two experiments were undertaken to assess the effect of temperature and nitrogen deposition composition on metal concentrations in soil solution. In each case, a common objective was to assess whether variation in metal concentrations in soil solution could be explained by changes in soil solution pH and DOC concentration. Lead concentrations in soil solution were modified by heating, but not the composition of nitrogen deposition, and lead showed a strong affinity for organic matter in soils and soil solution. Zinc concentrations were affected by both heating and nitrogen deposition, with the strongest effect being through changes in pH. However, in the case of both zinc and nickel, there were also associations with DOC concentrations, indicating that the organic phase becomes more significant for partitioning of metals between soil and soil solution in organic-rich soils. For copper, there was little effect of heating or nitrogen deposition, and the strongest association was with nitrate, rather than pH or DOC, in soil solution. Future research should be focused on more comprehensive studies dealing with the relationship between DOC, pH, climate, nitrogen deposition and metal in the field, with supporting laboratory experiments.
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Denton, Laura Elaine Scott. « Soil respiration at a Colorado subalpine forest ». Diss., Connect to online resource, 2005. http://wwwlib.umi.com/dissertations/fullcit/3165811.
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Hartley, Iain P. « The response of soil respiration to temperature ». Thesis, University of York, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.434021.
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Chang, Chao-Ting. « Soil water availability regulates soil respiration temperature dependence in Mediterranean forests ». Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/406082.
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The variations of ecosystem and soil respiration are mainly driven by temperature and precipitation, but the importance of temperature and precipitation could vary across temporal and spatial. At diurnal to annual temporal scales, ecosystem and soil respiration generally increase with average annual temperature, but very low or very high soil moisture has been shown to diminish the temperature response of respiration. Therefore, in water-limited ecosystem, such as the Mediterranean region where the seasonal pattern is characterized with significant summer drought, precipitation patterns are likely to play a particularly important role in regulating ecosystem and soil respiration inter annual whereas temperature may be much less factor. In this dissertation, I try to reduce the uncertainties of terrestrial net ecosystem exchange in Mediterranean region by measuring the interaction between environmental factors and soil respiration at short (i.e., diurnal) and medium (i.e., seasonal-years) temporal scales. Three in situ experiments were employed to investigate how soil respiration responds to environmental variations and management. Together, these three studies gave a consistent picture on how soil moisture strongly affects the dynamic and magnitude of soil respiration in Mediterranean forests. Results elucidated a clear soil moisture threshold; when soil moisture is above this threshold, soil temperature is the main driver of soil respiration, meanwhile, when soil moisture is below this threshold, soil respiration decoupled from soil temperature and is controlled by soil moisture. This suggests that soil moisture modified, at least in Mediterranean ecosystems, the temperature sensitivity of respiration through threshold-like response.Las variaciones de la respiración del ecosistema y del suelo son principalmente impulsadas por la temperatura y la precipitación, pero la importancia de la temperatura y la precipitación puede variar a lo largo del tiempo y el espacio. En las escalas temporales diurnas a anuales, la respiración del ecosistema y del suelo generalmente aumenta con la temperatura media anual, pero se ha demostrado que la humedad del suelo muy baja o muy alta disminuye la respuesta a la temperatura de la respiración. Por lo tanto, en ecosistemas con escasez de agua, como la región mediterránea, donde el patrón estacional se caracteriza por sequías significativas en verano, es probable que los patrones de precipitación jueguen un papel particularmente importante en la regulación de la respiración del ecosistema y del suelo. En esta tesis, intento reducir las incertidumbres del intercambio de ecosistemas netos terrestres en la región mediterránea midiendo la interacción entre los factores ambientales y la respiración del suelo a escalas temporales cortas (diurnas) y medias (estacionales). Se utilizaron tres experimentos in situ para investigar cómo la respiración del suelo responde a las variaciones y manejo del ambiente. En conjunto, estos tres estudios dieron una imagen consistente de cómo la humedad del suelo afecta fuertemente la dinámica y la magnitud de la respiración del suelo en los bosques mediterráneos. Los resultados dilucidaron un umbral claro de humedad del suelo; Cuando la humedad del suelo está por encima de este umbral, la temperatura del suelo es el principal impulsor de la respiración del suelo, mientras que la humedad del suelo está por debajo de este umbral, la respiración del suelo está desacoplada de la temperatura del suelo y controlada por la humedad del suelo. Esto sugiere que la humedad del suelo modificó, al menos en los ecosistemas mediterráneos, la sensibilidad a la temperatura de la respiración a través de la respuesta tipo umbral.
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Burns, Nancy Rosalind. « Soil organic matter stability and the temperature sensitivity of soil respiration ». Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/9922.
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Soil respiration is an important source of atmospheric CO2, with the potential for large positive feedbacks with global warming. The size of these feedbacks will depend on the relative sensitivity to temperature of very large global pools of highly stable soil organic matter (SOM), with residence times of centuries or longer. Conflicting evidence exists as to the relationships between temperature sensitivity of respiration and stability of SOM, as well as the temperature sensitivity of individual stabilisation mechanisms. This PhD considers the relationship between different stabilisation mechanisms and the temperature sensitivity of SOM decomposition. I used physical fractionation to isolate SOM pools with a variety of turnover rates, from decadal to centennially cycling SOM, in a peaty gley topsoil from Harwood Forest. Mean residence times of SOM as determined by 14C dating was most strongly affected by depth, providing stability on a millienial scale, while OM-mineral associations and physical protection of aggregates provided stability to around 500 years. Chemical characteristics of organic material in these fractions and whole soils (13C CP-MAS NMR spectroscopy, mass spectrometry, FTIR spectroscopy, thermogravimetric analysis, ICP-OES) indicated the relative contribution of different stabilisation mechanisms to the longevity of each of these fractions. Two long-term incubations of isolated physical fractions and soil horizons at different temperatures provided information about the actual resistance to decomposition in each SOM pool, as well as the temperature sensitivity of respiration from different pools. Naturally 13C-labelled labile substrate additions to the mineral and organic horizons compared the resistance to priming by labile and recalcitrant substrates. Manipulation of soil pore water was investigated as a method for isolating the respiration of SOM from physically occluded positions within the soil architecture. Contadictory lines of evidence emerged on the relative stability of different SOM pools from 14C dating, incubation experiments and chemical characterisation of indicators of stability. This led to the interpretation that physical aggregate protection primarily controls SOM stability within topsoils, while mineral and Fe oxide stability provides more lasting stability in the mineral horizon. Less humified and younger SOM was found to have a higher sensitivity to temperature than respiration from well-humified pools, in contrast to predictions from thermodynamics.
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Henry, Leigh-Anne. « Partitioning Between Soil-Adsorbed and Planktonic Escherichia coli ». Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/32255.
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A scarcity of comparable research on the transport of bacteria has forced hydrologic models to assume that bacteria travel as dissolved chemicals. In reality, most bacteria preferentially attach to soil aggregates, and behave very differently from planktonic bacteria. The goal of this research project was to identify and evaluate a laboratory method for partitioning between attached and planktonic bacteria that could be used to improve hydrologic modeling.
Attachment was measured indirectly as the difference between total and planktonic bacterial concentration. Planktonic concentration was defined as the concentration of bacteria that could pass through an 8 μm screen. Total concentration was determined by disaggregating attached bacteria through a dispersion treatment. A randomized complete block design was structured to test for the effects of filtering, two dispersion treatment options, and the presence of soil on concentration. Tween-85 surfactant was selected as the best dispersant for use in further studies. About 78% of bovine E. coli in the laboratory samples were adsorbed/associated with sterile soil particles. Twenty samples of different bacteria-soil ratios were analyzed using this method to develop an isotherm equation describing E. coli partitioning. The E. coli used to inoculate these samples was cultured using a chemostat reactor to control cell growth stage and control variability. A linear isotherm (R2=0.88) was selected to describe this experimental data; however, future studies characterizing the partitioning behavior of E. coli under different environmental conditions are recommended in order to better understand attachment prior to modeling attached and planktonic E. coli separately.
Master of Science
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Flynn, Conor R. « Soil Respiration Response to Disturbance in a Northern Michigan Forest ». The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1336919672.
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Kocyigit, Rasim. « Partitioning of Carbon and Carbon Dioxide in plant-soil systems / ». Search for this dissertation online, 2003. http://wwwlib.umi.com/cr/ksu/main.
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Iost, Susanne. « Soil respiration, microbial respiration and mineralisation in soils of montane rainforests of Southern Ecuador : influence of altitude ». Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1201126765623-42870.
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Impacts of land use and climate change in tropical forests on the global carbon budget are of principal interest in the recent research, as these forests amount to about 48 % of the world’s forested area. Interest has been focused on lowland tropical forests mainly, but tropical montane forests occupy about 20 % of all tropical forests. Soils of tropical montane forests are frequently waterlogged and characterised by high soil organic carbon stocks. Furthermore, along altitudinal gradients, changes in stand structure and net primary production can be observed that have not been fully explained yet. As causes reduced microbial activity and nitrogen turnover in soils of tropical montane forests have been suggested. Against the background of climate change, carbon turnover mechanisms in soils of these forests are of special interest. The present study therefore aimed at determining and quantifying relevant carbon and nitrogen pools as well as nitrogen mineralisation potentials. Furthermore, size, activity, and structure of microbial biomass were characterised. The collected data was supposed to provide basic knowledge on carbon and nitrogen cycling in tropical montane forest soils. Thus, evaluation of the susceptibility of their carbon stocks for climate change as well as nitrogen and carbon limitation of microbial organic matter decomposition was possible. Field work of this study was conducted during 2003–2005 at an altitudinal transect that in- cluded five study sites between 1 050 and 3 060 m amsl. Total soil respiration was recorded biweekly over two years, the contribution of roots to total soil CO2 efflux over one year. Soils of the study sites were sampled twice and biochemical and microbial parameters were determined.
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Iost, Susanne. « Soil respiration, microbial respiration and mineralisation in soils of montane rainforests of Southern Ecuador : influence of altitude ». Doctoral thesis, Technische Universität Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A24042.
Texte intégralRésumé :
Impacts of land use and climate change in tropical forests on the global carbon budget are of principal interest in the recent research, as these forests amount to about 48 % of the world’s forested area. Interest has been focused on lowland tropical forests mainly, but tropical montane forests occupy about 20 % of all tropical forests. Soils of tropical montane forests are frequently waterlogged and characterised by high soil organic carbon stocks. Furthermore, along altitudinal gradients, changes in stand structure and net primary production can be observed that have not been fully explained yet. As causes reduced microbial activity and nitrogen turnover in soils of tropical montane forests have been suggested. Against the background of climate change, carbon turnover mechanisms in soils of these forests are of special interest. The present study therefore aimed at determining and quantifying relevant carbon and nitrogen pools as well as nitrogen mineralisation potentials. Furthermore, size, activity, and structure of microbial biomass were characterised. The collected data was supposed to provide basic knowledge on carbon and nitrogen cycling in tropical montane forest soils. Thus, evaluation of the susceptibility of their carbon stocks for climate change as well as nitrogen and carbon limitation of microbial organic matter decomposition was possible. Field work of this study was conducted during 2003–2005 at an altitudinal transect that in- cluded five study sites between 1 050 and 3 060 m amsl. Total soil respiration was recorded biweekly over two years, the contribution of roots to total soil CO2 efflux over one year. Soils of the study sites were sampled twice and biochemical and microbial parameters were determined.
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Henderson, Rachel A. « Partitioning Soil CO2 Efflux through Vertical Profiles of Manipulated Forests in MOFEP ». University of Toledo / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1177701393.
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Hung, Hayley Hing Ning. « Partitioning and transport of organic compounds in air-plant-soil systems ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0023/NQ49830.pdf.
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Selig, Marcus Franklin. « Soil Co2 Efflux and Soil Carbon Content as Influenced by Thinning in Loblolly Pine Plantations on the Piedmont of Virginia ». Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/33866.
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The thinning of loblolly pine plantations has a great potential to influence the fluxes and storage of carbon within managed stands. This study looked at the effects of thinning on aboveground carbon and mineral soil carbon storage, 14-years after the thinning of an 8-year-old loblolly pine plantation on the piedmont of Virginia. The study also examined soil respiration for one year following the second thinning of the same stand at age twenty-two. The study was conducted using three replicate .222 hectare stands planted using 3.05 by 3.05 meter spacing in 1980 at the Reynolds Homestead in Critz, VA.
Using two different sample collection methods it was determined that soil carbon was evenly dispersed throughout thinned plots, and that random sampling techniques were adequate for capturing spatial variability. Soil carbon showed a significant negative correlation with soil depth (p=0.0001), and by testing the difference between intercepts in this relationship, it was determined that thinning significantly increased soil carbon by 31.9% across all depths (p=0.0004). However, after accounting for losses in aboveground wood production, thinning resulted in an overall 10% loss in stand carbon storage. However, this analysis did not take into account the fate of wood products following removal.
Soil respiration, soil temperature, and soil moisture were measured every month for one year near randomly selected stumps and trees. In order to account for spatial variation, split plots were measured at positions adjacent to stumps and 1.5 meters away from stumps. Soil temperature and moisture were both significantly affected by thinning. Regression analysis was performed to determine significant drivers in soil CO2 efflux. Temperature proved to be the most significant driver of soil respiration, with a positive correlation in thinned and unthinned stands. When modeled using regression, thinning was a significant variable for predicting soil respiration (p < 0.0009), but explained only 3.4% of the variation. The effects of thinning were responsible for decreased respiration, however, when coupled with increased temperatures, soil respiration was elevated in thinned stands.Master of Science
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De, Remy De Courcelles Vivien. « Studies of soil respiration in eucalypt forests of south east Australia ». Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/10422.
Texte intégralRésumé :
This thesis addresses gaps in knowledge of soil respiration in forests of south-east Australia. Soil respiration plays a major part in the cycle of carbon between soils - the biggest pool of terrestrial carbon - and the atmosphere. Despite its global significance, we have only a limited understanding of the magnitude and responses of soil respiration, and especially of its components, to abiotic (temperature, moisture, soil fertility) and biotic (photosynthesis, seasonality of belowground C allocation patterns and root growth, quality and quantity of above and belowground litter) controls. Furthermore, vegetation type may modulate the influences of these abiotic and biotic controls and with soil respiration research having been based mostly in the northern hemisphere, it is crucial that regional studies be conducted further afield. This thesis also considers the context of the current increase in atmospheric [CO2] and resulting predicted climate change that will directly or indirectly impact on soil respiration through extreme weather events, changes in the frequency and intensity of fires or increase in growth. Using both field and laboratory based techniques I measured respiration from soils supporting a variety of Eucalypts. Elevated atmospheric [CO2] did not have an effect on rates of soil respiration in a Eucalyptus saligna plantation, contrary to usual findings. Drought on the other hand slowed rates of respiration, owing to a slowing of the transfer of photosynthates from leaves to roots. The impact of an increase in above-ground litter deposition, a possible consequence of extreme weather events, or continuous increase in primary production can be subdued by the nature and quality of the litter in Eucalyptus pauciflora woodlands. No effect was recorded in the field but ground litter added to soils in the laboratory triggered a response including a priming effect. Root priming effect was also found to increase basal heterotrophic respiration by 54% on average in Eucalyptus regnans. The study on the contribution of roots to total soil respiration showed that it is necessary to use hybrid techniques to separate and estimates the contribution of components of soil respiration; in this thesis’ case the use of collars and chambers in the field and respirometer in the laboratory was determinant in identifying root priming effect. Great spatial variation in respiration rates was measured both in the simple ecosystem of a Eucalyptus saligna plantation and as a result of fire disturbance at the Messmate 1 site supporting Eucalyptus obliqua and Eucalyptus radiata. Finally, a synthesis of the results of the whole thesis considered the effect of soil temperature on soil respiration and showed that contrary to what is commonly agreed by the Q10 model, respiration rates reached a plateau for temperatures between 16°C to 23°C.
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Kuntz, Marianne. « Carbon : an important regulator of denitrification in arable soil ». Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=232081.
Texte intégralRésumé :
Carbon (C) as a driver of soil denitrification was investigated in a series of four laboratory incubation experiments employing stable nitrogen (N) and C isotope approaches. The research addressed the lack of knowledge on mechanisms through which the quantity and quality of organic‐C containing substrates interact with denitrification. The amount of organic matter added to soil was manipulated to relate C respiration with process rates of denitrification. Respiration derived from dissolved organic matter C was linearly related to denitrification but the direction of the relationship was variable in time. This may be most likely an effect of changing quality of the C available and possibly microbial community structure. Nitrous oxide (N2O) emission from denitrification at the later stages of residue decomposition was driven by nitrate (NO3‐) accumulation in the soil rather than C provided by the residue. Denitrification across a vertical shallow soil profile formed in a laboratory microcosm was investigated. A surface hotspot formed immediately as a response to residue‐C addition and increased rates of N2O production. N2O reduction occurred at depth. The hotspot at depth was related to an indirect effect of residue‐C, which was depletion of O2. Further, to address the complexity of low molecular weight C substrate available to denitrifiers in the soil solution, denitrification rates in response to glucose, citric acid and glutamic acid supplied individually versus in mixture were characterised. Carbon substrate quality regulated N2O production rates via interactions within the soil microbial community and with the soil solid phase. Overall, the experiments showed that C stimulates strong N2O emission peaks and increase cumulative N2O emissions from arable soil along a gradient of varying C substrate complexity and quantity. Interaction in space and time play an important role when C containing inputs affected other proximal drivers of denitrification such as NO3‐ and O2.
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Russell, Kerri Ann. « Microbial and Environmental Drivers of Soil Respiration Differ Along Montane to Urban Transitions ». BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7718.
Texte intégralRésumé :
In natural ecosystems, like deciduous and coniferous forests, soil CO2 flux or soil respiration is highly variable and influenced by multiple factors including temperature, precipitation, dissolved soil organic carbon (DOC), dissolved organic matter (DOM), and bacterial and fungal biomass and diversity. However, as the human population continues to grow rapidly, so too do urbanized landscapes with unknown consequences to soil respiration. To determine the extent urbanization influences seasonal shifts in microorganisms and environmental drivers alter soil respiration, we evaluated bacterial and fungal communities, soil physiochemical characteristics, and respiration in forested and urbanizing ecosystems in three watersheds across northern Utah, USA. Based on the next-generation sequencing of the 16s DNA and RNA, we found that montane bacteria were predominantly structured by season while urban bacteria were influenced by degree of urbanization. There was no apparent effect of season on montane fungi, but urban fungal communities followed patterns similar to urban bacterial communities. Bacterial diversity was sensitive to seasonality, especially in montane ecosystems, declining 21-34% from spring to summer and staying relatively low into fall, and fungal diversity was generally depressed in spring. Urban bacterial communities were differentiated by substantially more bacterial taxa with 62 unique OTUs within families structing phylogenetic differences compared with only 18 taxa differentiating montane communities. Similar to bacteria and fungi, DOC and ammonium concentrations fluctuated predominantly by season while these same parameters where highly variable among urban soils among the three watersheds. Structural components of DOM via parallel factor analysis (PARAFAC) of fluorescence excitation-emission matrices show varying patterns between montane and urban systems with humic substance resistance to biodegradability found more dominantly in montane systems. Incorporating all soil chemical parameters, daily temperature and moisture, and fungal and bacterial diversity and richness in mixed linear effects models describing daily CO2 over all seasons, we found that a single model best described montane soil respiration, while individual watershed models best described urban respiration. Montane respiration was related to the availability of DOC, different DOM components, and rRNA-based bacterial diversity . Alternatively, urban respiration was influenced by either bacterial diversity and richness in our rapidly urbanizing environment, DOM characteristics and soil O2 in the more agricultural urban soils, or the DOM parameter humification index (HIX) in highly urbanized soils. Our results suggest that urbanization creates distinct bacterial and fungal communities with a single soil biotic or chemical parameter structuring soil respiration, while montane ecosystems select for similar bacterial and fungal communities with respiration sensitive to fluctuations in soil moisture, bacteria and the recalcitrance of carbon (C) resources.
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Wiseman, P. Eric. « Soil Carbon Dioxide Efflux Across Four Age Classes Of Plantation Loblolly Pine (Pinus taeda L.)On The Virginia Piedmont ». Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/35770.
Texte intégralRésumé :
Soil carbon dioxide efflux resulting from microbial and root respiration is a major component of the forest carbon cycle. We undertook this investigation to better understand the nature of soil carbon dioxide efflux of plantation loblolly pine, an important ecological and economical resource in the southeastern United States. Specifically, we hoped to learn how soil carbon dioxide efflux differs both spatially and temporally for four age classes of plantation loblolly pine on the Virginia piedmont. During a 12-month period, soil carbon dioxide efflux was repeatedly measured for four age classes of plantation loblolly pine using a dynamic, closed-chamber infrared gas analyzer. The age classes examined were 1- to 2-year-old, 4- to 6-year-old, 8- to 12-year-old, and 20- to 25-year-old stands. Mean soil carbon dioxide efflux rates measured during the 12-month study were 1.72, 2.58, 2.84, and 2.90 micromole/sq m/s for 1- to 2-year-old, 4- to 6-year-old, 8- to 12-year-old, and 20- to 25-year-old stands, respectively. Stand age had a significant effect on efflux rate during 10 of the 12 monthly sampling sessions. Additionally, mean efflux rates were consistently higher near the tree and a significant positional difference was detected during 8 of the 12 monthly sampling sessions. Mean soil carbon dioxide efflux rates, by position, for the 12-month study were 2.72 and 2.28 micromole/sq m/s for the near and away measurement positions, respectively. Based on monthly mean soil carbon dioxide efflux rates, annual carbon losses were estimated at 651, 976, 1074, and 1082 g C/sq m/yr for 1- to 2-year-old, 4- to 6-year-old, 8- to 12-year-old, and 20- to 25-year-old stands, respectively. Regression analysis was used to examine the influence of soil and climatic factors on seasonal changes in soil carbon dioxide efflux. The most influential factors affecting soil carbon dioxide efflux during the 12-month study were soil temperature, soil moisture, stand age, and measurement position. We believe respiring roots significantly influence soil carbon dioxide efflux of plantation loblolly pine and account for differences observed between stands of different ages as well as spatial differences observed within a given stand.Master of Science
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Henderson, Rachel. « Partitioning soil CO₂ efflux through vertical profiles of manipulated forests in MOFEP / ». Connect to Online Resource-OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=toledo1177701393.
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Hu, Duan. « Soil respiration following alternative site preparation treatments in a boreal mixedwood forest ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1996. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/MQ33389.pdf.
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Maher, Ryan Matthew. « Soil respiration and plant growth across a chronosequence of tallgrass prairie reconstructions ». [Ames, Iowa : Iowa State University], 2007.
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Nietz, Jennifer Goedhart. « Soil Respiration During Partial Canopy Senescence in a Northern Mixed Deciduous Forest ». The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1276543755.
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Xu, Jianye. « Interannual Dynamics of Soil Respiration in Managed Oak Forests in Missouri Ozarks ». University of Toledo / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1251397682.
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Knox, Oliver Gimli Gunning. « Exploiting nitrate respiration to optimise antagonistic control of root disease in soil ». Thesis, University of Aberdeen, 2000. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602312.
Texte intégralRésumé :
In soils of high matric potential, low oxygen conditions often develop that favour disease development by many soil-borne plant pathogens. The introduction of a third party, or biocontrol agent, to suppress disease development would require that the agent remains metabolically active under such conditions. In the rhizosphere, plant roots not only supply carbon as an electron donor but cause a localised lowering of oxygen concentrations, conditions favourable for nitrate respiration. The effect of the addition of nitrate on the activity of antagonistic strains of Bacillus subtilis, Pseudomonas fluorescens and P. corrugata was studied in vitro on agar plates, but no significant (P 0.05) quantitative effect was observed . A sealed plate method, using aerobic, anoxic, and anaerobic conditions with 0, 1, 2.5, 5, 10 and 100mM nitrate concentrations was investigated using the B. subtilis strains. This assay tested the activity of antifungal volatiles (AFV) produced by the bacteria. The results indicated that nitrate led to an increased AFV production and/or activity against fungal pathogens under anoxic conditions with nitrate at or above 10 mM. To investigate root colonisation and the establishment of biocontrol colonies in the rhizosphere, lux marking of the biocontrol bacterial strains was undertaken. The transformed bioluminescent B. subtilis strains lost the ability to antagonise the test fungi on agar plates. This loss of antagonism appeared to be due to luciferase utilising metabolites involved in antibiosis and producing a low, but significantly different (P ?0.05) from background and parental strains level of luminescence. The effects of nitrate on a soil based biocontrol system were studied in greenhouse trials. Unfortunately, disease failed to develop, and the effects of the addition of nitrate could not be assessed. The potential involvement of nitrate in maintaining certain biocontrol aspects under conditions that favour pathogen attack seems likely from in vitro based studies. The removal of the antagonistic phenotype, from lux marked B. subtilis strains, raised questions as to the suitability of luciferase for use in this system and highlighted the need for careful monitoring and screening of genetically modified organisms.
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Moyano, Fernando Esteban. « Soil respiration fluxes and controlling factors in temperate forest and cropland ecosystems ». [S.l. : s.n.], 2007.
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Xu, Jianye. « Interannual dynamics of soil respiration in managed oak forrests in Missouri Ozarks / ». Connect to full text in OhioLINK ETD Center, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1251397682.
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Thesis (M.S.)--University of Toledo, 2009.Typescript. "Submitted as partial fulfillment of the requirements for the Master of Science in Biology." "A thesis entitled"--at head of title. Bibliography: leaves 48-55.
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Tyree, Michael Christopher. « The Short-term Effects of Fertilization on Total Soil CO2 Efflux, Heterotrophic, and Autotrophic Respiration of Loblolly Pine (Pinus taeda L.) ». Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/34944.
Texte intégralRésumé :
Fertilization is a common, cost effective treatment for increasing forest productivity within managed forests of the southeastern United States. However, little is known about how fertilization affects the below-ground processes that drive soil CO2 efflux in loblolly pine (Pinus taeda L.). A thorough understanding of below-ground carbon dynamics is necessary for the estimation of net ecosystem productivity and the carbon storage potential of these managed systems.
In April 2004, we began monitoring total soil CO2 efflux (EC), heterotrophic (RH), and root respiration (RR) in response to fertilization with diammonium phosphate (DAP). Respiratory components were measured prior to fertilization, weekly following fertilization, and bi-weekly after respiratory components stabilized using a dynamic closed chamber and an infrared gas analyzer. We found that EC differed significantly (P<0.0001) between fertilized and unfertilized plots, but the direction was dependent on date. In the early period of the study, fertilized plot values were lower than control plots. However, by the latter periods fertilized plot values returned to control levels except for one sampling date in March 2005 when fertilized plot values were greater then control plots. Heterotrophic respiration was consistently and significantly (P=0.0002) lower in fertilized plots. Root respiration was significantly (P=0.0597) increased in fertilized plots when analyzed over the study and showed a 20% increase due to fertilization. We concluded that an increase in RR and possibly root biomass was enough to balance the decrease in RH leading to no difference in EC later in the growing season.
We performed a pair of greenhouse studies to observe the effects of fertilization in the form of diammonium phosphate (DAP) on RR. The objectives were to determine how nutrient additions initially affect RR in one-year-old loblolly pine seedlings. Secondly, we wanted to determine if Captan [N-(trichloromethylthio) cyclohex-4-ene-1, 2-dicarboximide], a mild fungicide, could be used to reduce or eliminate ecto-mycorrhizae upon visual inspection. Both studies showed that initially, at a high rate (100 ppm N and 49 ppm P) of fertilization, RR was significantly (P<0.10) increased relative to seedlings that did not receive fertilization. This increase was only temporary with rates returning to, or decreasing below, control levels by the end of the study. No consistent trend was found between low (25 ppm N and 13 ppm P) and moderate (50 ppm N and 25 ppm P) rates of fertilization. Captan was shown to generally have no affect on RR. Captan and fertilization both showed (visual inspection) a decrease in fine-roots and mycorrhizae, which could explain the reduction in respiration rates observed in these treatments by the end of the studies.
Master of Science
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Wong, Vanessa, et u2514228@anu edu au. « The effects of salinity and sodicity on soil organic carbon stocks and fluxes ». The Australian National University. Faculty of Science, 2007. http://thesis.anu.edu.au./public/adt-ANU20080428.223144.
Texte intégralRésumé :
Soil is the worlds largest terrestrial carbon (C) sink, and is estimated to contain approximately 1600 Pg of carbon to a depth of one metre. The distribution of soil organic C (SOC) largely follows gradients similar to biomass accumulation, increasing with increasing precipitation and decreasing temperature. As a result, SOC levels are a function of inputs, dominated by plant litter contributions and rhizodeposition, and losses such as leaching, erosion and heterotrophic respiration. Therefore, changes in biomass inputs, or organic matter accumulation, will most likely also alter these levels in soils. Although the soil microbial biomass (SMB) only comprises 1-5% of soil organic matter (SOM), it is critical in organic matter decomposition and can provide an early indicator of SOM dynamics as a whole due to its faster turnover time, and hence, can be used to determine soil C dynamics under changing environmental conditions.¶
Approximately 932 million ha of land worldwide are degraded due to salinity and sodicity, usually coinciding with land available for agriculture, with salinity affecting 23% of arable land while saline-sodic soils affect a further 10%. Soils affected by salinity, that is, those soils high in soluble salts, are characterised by rising watertables and waterlogging of lower-lying areas in the landscape. Sodic soils are high in exchangeable sodium, and slake and disperse upon wetting to form massive hardsetting structures. Upon drying, sodic soils suffer from poor soil-water relations largely related to decreased permeability, low infiltration capacity and the formation of surface crusts. In these degraded areas, SOC levels are likely to be affected by declining vegetation health and hence, decreasing biomass inputs and concomitant lower levels of organic matter accumulation. Moreover, potential SOC losses can also be affected from dispersed aggregates due to sodicity and solubilisation of SOM due to salinity. However, few studies are available that unambiguously demonstrate the effect of increasing salinity and sodicity on C dynamics. This thesis describes a range of laboratory and field investigations on the effects of salinity and sodicity on SOC dynamics.¶
In this research, the effects of a range of salinity and sodicity levels on C dynamics were determined by subjecting a vegetated soil from Bevendale, New South Wales (NSW) to one of six treatments. A low, mid or high salinity solution (EC 0.5, 10 or 30 dS/m) combined with a low or high sodicity solution (SAR 1 or 30) in a factorial design was leached through a non-degraded soil in a controlled environment. Soil respiration and the SMB were measured over a 12-week experimental period. The greatest increases in SMB occurred in treatments of high-salinity high-sodicity, and high-salinity low-sodicity. This was attributed to solubilisation of SOM which provided additional substrate for decomposition for the microbial population. Thus,
as salinity and sodicity increase in the field, soil C is likely to be rapidly lost as a result of increased mineralisation.¶
Gypsum is the most commonly-used ameliorant in the rehabilitation of sodic and saline-sodic soils affected by adverse soil environmental conditions. When soils were sampled from two sodic profiles in salt-scalded areas at Bevendale and Young, SMB levels and soil respiration rates measured in the laboratory were found to be low in the sodic soil compared to normal non-degraded soils. When the sodic soils were treated with gypsum, there was no change in the SMB and respiration rates. The low levels of SMB and respiration rates were due to low SOC levels as a result of little or no C input into the soils of these highly degraded landscapes, as the high salinity and high sodicity levels have resulted in vegetation death. However, following the addition of organic material to the scalded soils, in the form of coarsely-ground kangaroo grass, SMB levels and respiration rates increased to levels greater than those found in the non-degraded soil. The addition of gypsum (with organic material) gave no additional increases in the SMB.¶
The level of SOC stocks in salt-scalded, vegetated and revegetated profiles was also determined, so that the amount of SOC lost due to salinisation and sodication, and the increase in SOC following revegetation relative to the amount of SOC in a vegetated profile could be ascertained. Results showed up to three times less SOC in salt-scalded profiles compared to vegetated profiles under native pasture, while revegetation of formerly scalded areas with introduced pasture displayed SOC levels comparable to those under native pasture to a depth of 30 cm. However, SOC stocks can be underestimated in saline and sodic landscapes by setting the lower boundary at 30 cm due to the presence of waterlogging, which commonly occurs at a depth greater than 30 cm in saline and sodic landscapes as a result of the presence of high or perched watertables. These results indicate that successful revegetation of scalded areas has the potential to accumulate SOC stocks similar to those found prior to degradation.¶
The experimental results from this project indicate that in salt-affected landscapes, initial increases in salinity and sodicity result in rapid C mineralisation. Biomass inputs also decrease due to declining vegetation health, followed by further losses as a result of leaching and erosion. The remaining native SOM is then mineralised, until very low SOC stocks remain. However, the C sequestration potential in these degraded areas is high, particularly if rehabilitation efforts are successful in reducing salinity and sodicity. Soil ecosystem functions can then be restored if organic material is available as C stock and for decomposition in the form of either added organic material or inputs from vegetation when these salt-affected landscapes are revegetated.
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Nichols, Lara Kaitlin. « Relationships Among Soil Properties and Soil CO2 Efflux in a Loblolly Pine-Switchgrass Intercropped System ». Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/51945.
Texte intégralRésumé :
The components of soil CO2 efflux are affected by many soil properties including temperature, moisture, microbial abundance and activity, and other soil physical and chemical properties. Changes in these factors can result in high spatial and temporal variability of total soil CO2 efflux. Low molecular weight organic acids (LMWOAs), dissolved organic carbon (DOC) and dissolved organic nitrogen (DON), microbial biomass and activity were measured to evaluate the impact of intercropping switchgrass (Panicum virgatum L.) in a loblolly pine (Pinus taeda L.) plantation. Surface soil samples (0-15 cm) were collected on the bed (PSG-B), interbed (PSG-I) and edge (PSG-E) of pine-switchgrass intercropped treatments, as well as pine only (P-B) and switchgrass only (SG-I) treatments. Differences in most soil properties and processes of intercropped treatments were sporadic and most did not show clear trends. However, significant correlations between DOC, soil temperature, oxalic and acetic acids and soil CO2 efflux were present. In an multiple regression model these factors explained 57% of the variance in total soil CO2 efflux. Therefore we think that LMWOAs, as a labile component of DOC, are influencing total CO2 efflux because they are being consumed by microbial community, increasing heterotrophic respiration and as a result overall total CO2 efflux. The amount and distribution of labile C controls microbial community dynamics, heterotrophic respiration as well as the stabilization of soil C.Master of Science
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Jenkins, Meaghan Edith Biological Earth & Environmental Sciences Faculty of Science UNSW. « Carbon cycling in sub-alpine ecosystems ». Awarded by:University of New South Wales. Biological, Earth & ; Environmental Sciences, 2009. http://handle.unsw.edu.au/1959.4/44822.
Texte intégralRésumé :
The relationship between temperature and soil respiration has been well explored although uncertainties remain. This thesis examined the relationship between temperature and rates of heterotrophic respiration in soils from three adjacent sub-alpine Australian vegetation types; woodland, shrubland and grassland. Temperature sensitivity of soil (Q10) has recently been a hotly debate topic, one side concluding that decomposition of recalcitrant, less labile components of soil organic matter are insensitive to temperature. Whilst others argue that there is no difference in the temperature sensitivities of labile and recalcitrant carbon pools. Robust modeling of rates of soil respiration requires characterization of the temperature response of both labile and recalcitrant pools. Laboratory incubation provides a means of characterizing the temperature response of rates of respiration whilst reducing the confounding effects encountered in the field, such as seasonal fluctuations in temperature, moisture and substrate supply. I used a novel system that allowed laboratory measurement of gas exchange in soils over a range of temperatures under controlled conditions. Measurements included CO2 efflux and O2 uptake over a range of temperatures from 5 to 40oC, characterization of temperature response and sensitivity, and respiratory quotients. Rates of heterotrophic respiration fitted both exponential and Arrhenius functions and temperature sensitivity varied and depended on the model used, vegetation type and depth in the soil profile. Long-term incubation indicated both labile and resistant pools of carbon had similar temperature sensitivities. Respiratory quotients provided a strongly predictive measure of the potential rate of decomposition of soil C, independent of the temperature response of respiration, providing a tool that may be used alongside derived parameters to help understand shifts in microbial use of C substrates. Vegetation type influenced soil chemical properties and rates of heterotrophic respiration. Rates of respiration correlated well with concentrations of carbon and nitrogen as has been previously observed, unlike previous studies however a positive correlation was observed between indices of plant available phosphorus and respiration. The soils examined were from three adjacent vegetation types formed on common geology, I concluded that vegetation type had a significant influence on soil, in contrast to the commonly held view by ecologists that soil type drives patterns in vegetation. Climatic effects such as longer, dryer hotter summer, reduced snow cover and increased incidence of extreme weather events such as frosts and bushfire are likely to drive patterns in vegetation in this region and therefore have a significant impact on carbon cycling in Sub-alpine Australian soils.
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Comstedt, Daniel. « Explaining temporal variations in soil respiration rates and delta13C in coniferous forest ecosystems ». Doctoral thesis, Örebro universitet, Institutionen för naturvetenskap, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-2055.
Texte intégralRésumé :
Soils of Northern Hemisphere forests contain a large part of the global terrestrial carbon (C) pool. Even small changes in this pool can have large impact on atmospheric [CO2] and the global climate. Soil respiration is the largest terrestrial C flux to the atmosphere and can be divided into autotrophic (from roots, mycorrhizal hyphae and associated microbes) and heterotrophic (from decomposers of organic material) respiration. It is therefore crucial to establish how the two components will respond to changing environmental factors. In this thesis I studied the effect of elevated atmospheric [CO2] (+340 ppm, 13C-depleted) and elevated air temperature (2.8-3.5 oC) on soil respiration in a whole-tree chamber (WTC) experiment conducted in a boreal Norway spruce forest. In another spruce forest I used multivariate modelling to establish the link between day-to-day variations in soil respiration rates and its δ13C, and above and below ground abiotic conditions. In both forests, variation in δ13C was used as a marker for autotrophic respiration. A trenching experiment was conducted in the latter forest in order to separate the two components of soil respiration. The potential problems associated with the trenching, increased root decomposition and changed soil moisture conditions were handled by empirical modelling. The WTC experiment showed that elevated [CO2] but not temperature resulted in 48 to 62% increased soil respiration rates. The CO2-induced increase was in absolute numbers relatively insensitive to seasonal changes in soil temperature and data on δ13C suggest it mostly resulted from increased autotrophic respiration. From the multivariate modelling we observed a strong link between weather (air temperature and vapour pressure deficit) and the day-to-day variation of soil respiration rate and its δ13C. However, the tightness of the link was dependent on good weather for up to a week before the respiration sampling. Changes in soil respiration rates showed a lag to weather conditions of 2-4 days, which was 1-3 days shorter than for the δ13C signal. We hypothesised to be due to pressure concentration waves moving in the phloem at higher rates than the solute itself (i.e., the δ13C–label). Results from the empirical modelling in the trenching experiment show that autotrophic respiration contributed to about 50% of total soil respiration, had a great day-to-day variation and was correlated to total soil respiration while not to soil temperature or soil moisture. Over the first five months after the trenching, an estimated 45% of respiration from the trenched plots was an artefact of the treatment. Of this, 29% was a water difference effect and 16% resulted from root decomposition. In conclusion, elevated [CO2] caused an increased C flux to the roots but this C was rapidly respired and has probably not caused changes in the C stored in root biomass or in soil organic matter in this N-limited forest. Autotrophic respiration seems to be strongly influenced by the availability of newly produced substrates and rather insensitive to changes in soil temperature. Root trenching artefacts can be compensated for by empirical modelling, an alternative to the sequential root harvesting technique.
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Boström, Björn. « Achieving carbon isotope mass balance in Northern forest soils, soil respiration and fungi / ». Örebro : Department of Natural Sciences, Örebro University, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-2101.
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Smith, Daniel Robert. « Soil respiration in a fire scar chronosequence of Canadian boreal jack pine forest ». Thesis, University of Leicester, 2009. http://hdl.handle.net/2381/8268.
Texte intégralRésumé :
This research investigates soil respiration (Rs) in a boreal jack pine (Pinus banksiana Lamb.) fire scar chronosequence at Sharpsand Creek, Ontario, Canada. During two field campaigns in 2006 and 2007, Rs was measured in a chronosequence of fire scars in the range 0 to 59 years since fire. Mean Rs adjusted for soil temperature (Ts) and soil moisture (Ms) (Rs T,M) ranged from 0.56 μmol CO2/m2/s (32 years post fire) to 8.18 μmol CO2/m2/s (58 years post fire). Coefficient of variation (CV) of Rs adjusted for Ts and Ms ranged from 20% (16 years post fire) to 56% (58 years post fire). Across the field site, there was a significant exponential relationship between Rs adjusted for soil organic carbon (Cs) and Ts (P = 1.24*10-06; Q10 = 2.21) but no effect of Ms on Rs adjusted for Cs and Ts for the range 0.21 to 0.77 volumetric Ms (P = 0.702). Rs T,M significantly (P = 0.030) decreased after burning mature forest, though no significant (P > 0.1) difference could be detected between recently burned and unburned young forest. Rs was measured in recently burned boreal jack pine fire scar age categories that differed in their burn history and there was a significant difference in Rs T,M between previously 32 v 16 year old (P = 0.000) and previously 32 v 59 year old (P = 0.044) scars. There was a strong significant exponential increase in S R T,M with time since fire (r2 = 0.999; P = 0.006) for the chronosequence 0, 16 and 59 years post fire, and for all these age categories, Rs T,M was significantly different from one another (P < 0.05). The Joint UK Land Environment Simulator (JULES) was used to model vegetation re-growth over successional time at Sharpsand Creek, though it appeared to perform poorly in simulating leaf area index and canopy height. JULES probably over estimated heterotrophic Rs at Sharpsand Creek when Ts corrected simulated values were compared with measured Rs T,M. The results of this study contribute to a better quantitative understanding of Rs in boreal jack pine fire scars and will facilitate improvements in C cycle modelling. Further work is needed in quantifying autotrophic and heterotrophic contributions to soil respiration in jack pine systems, monitoring soil respiration for extended time periods after fire and improving the ability of JULES to simulate successional vegetation re-growth.
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Jian, Jinshi. « Global soil respiration : interaction with macroscale environmental variables and response to climate change ». Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/92195.
Texte intégralRésumé :
The response of global soil respiration (Rs) to climate change determines how long the land can continue acting as a carbon sink in the future. This dissertation research identifies how temporal and spatial variation in environmental factors affects global scale Rs modeling and predictions of future Rs under global warming. Chapter 1 describes the recommend time range for measuring Rs across differing climates, biomes, and seasons and found that the best time for measuring the daily mean Rs is 10:00 am in almost all climates and biomes. Chapter 2 describes commonly used surrogates in Rs modeling and shows that air temperature and soil temperature are highly correlated and that they explain similar amounts of Rs variation; however, average monthly precipitation between 1961 and 2014, rather than monthly precipitation for a specific year, is a better predictor in global Rs modeling. Chapter 3 quantifies the uncertainty generated by four different assumptions of global Rs models. Results demonstrate that the time-scale of the data, among other sources, creates a substantial difference in global estimates, where the estimate of global annual Rs based on monthly Rs data (70.85 to 80.99 Pg C yr-1) is substantially lower than the current benchmark for land models (98 Pg C yr-1). Chapter 4 simulates future global Rs rates based on two temperature scenarios and demonstrates that temperature sensitivity of Rs will decline in warm climates where the level of global warming will reach 3°C by 2100 relative to current air temperature; however, these regional decelerations will be offset by large Rs accelerations in the boreal and polar regions. Chapter 5 compares CO2 fluxes from turfgrass and wooded areas of five parks in Blacksburg, VA and tests the ability of the Denitrification-Decomposition model to estimate soil temperature, moisture and CO2 flux across the seasons.
Cumulatively, this work provides new insights into the current and future spatial and temporal heterogeneity of Rs and its relationship with environmental factors, as well as key insights in upscaling methodology that will help to constrain global Rs estimates and predict how global Rs will respond to global warming in the future.Ph. D.
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Sawada, Kozue. « Quantitative Analysis of Soil Microbial Respiration using a Concept of Stepwise Substrate Utilization ». Kyoto University, 2010. http://hdl.handle.net/2433/120465.
Texte intégralRésumé :
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第15422号
農博第1807号
新制||農||979(附属図書館)
学位論文||H22||N4521(農学部図書室)
27900
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 舟川 晋也, 教授 二井 一禎, 教授 北山 兼弘
学位規則第4条第1項該当
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Stielstra, Clare M. « Quantifying the Role of Hydrologic Variability in Soil Carbon Flux ». Thesis, The University of Arizona, 2012. http://hdl.handle.net/10150/238914.
Texte intégralRésumé :
Soil carbon (C) is the largest terrestrial carbon pool. While inputs to this system are fairly well constrained, the diverse factors driving soil C efflux remain poorly understood. Carbon in surface soils is mobilized via two distinct pathways: CO₂ gas flux and dissolved C flux. The goal of this study was to quantify the role of hydrologic variability in mobilizing carbon as gaseous and dissolved fluxes from near-surface soils, and to determine their relative magnitudes. Data were collected through 2010 and 2011 from two subalpine sites in Arizona and New Mexico. I observed no significant variability in dissolved fluxes, and these values were low at all sites. In contrast, CO₂ fluxes were large (from 0.22 g C m⁻² d⁻¹ to 5.27 g C m⁻² d⁻¹) and varied between sites and between years. My results suggest that in arid montane forests soil carbon flux is critically linked to water availability.
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Nicot, Jean-Philippe. « Inverse modeling of subsurface environmental partitioning tracer tests / ». Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Al, Fassi Fahad Abdulrahman. « The microbial ecology of heathland soil with special reference to factors affecting microbial biomass and activity ». Thesis, University of Sheffield, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318137.
Texte intégral
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Barton, Catherine Arundel. « The measurement, partitioning and near-field modeling of perfluorooctanoate (PFO) in air ». Access to citation, abstract and download form provided by ProQuest Information and Learning Company ; downloadable PDF file, 191 p, 2008. http://proquest.umi.com/pqdweb?did=1601522501&sid=9&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Staddon, Philip L. « The partitioning of carbon in mycorrhizal plants grown at elevated atmospheric COâ†2 concentration ». Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265372.
Texte intégral
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Almeida, Risely Ferraz [UNESP]. « CO2 emission and O2 uptake of soil under different systems ». Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/149886.
Texte intégralRésumé :
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O oxigênio (O2) e o dióxido de carbono (CO2) no solo são os dois principais gases relacionados com a atividade dos microorganismos no solo. Assim, esta tese foi desenvolvida para observar a concentração e a relação entre a concentração do CO2 e O2 sob diferentes sistemas de resíduos. Para isso, realizamos dois experimentos de solo no Brasil e nos EUA, respectivamente. O primeiro experimento foi desenvolvido para examinar a relação entre fluxo de CO2 (FCO2) e o fluxo de O2 (FO2) usando a umidade do solo e o O2 como um predictor da respiração do solo em uma área de cana-de-açúcar sob diferentes manejos de resíduos (colheita mecânica - GH versus colheita queimada – BH). Portanto, os resultados do primeiro experimento estão descritos no Capítulo 2 e sendo intitulado de "Uso da captura de O2 como índice de respiração de CO2 em áreas de cana-de-açúcar sob diferentes manejos". O segundo experimento do solo observou o impacto do biochar na emissão ou sorção de CO2 e O2 nos solos. Assim, foram estudados três tipos de solos (Rosemount - RM, Potting Sol Sunshine - PS e UM), cinco biochars diferentes (biochar de chip de pinho - ICM, biochar de Carvalho Oak Royal - RO, biochar Acurel ativado - AAC, biochar de Bambu - B; biochar de Macadâmia - MC) e o tratamento controle (solo sem biochar). Consequentemente, os resultados foram descritos no Capítulo 3 e intitulado "Como a captura de O2 pode nos ajudar a entender os processos de sorção de CO2 via biochar?". Assim, nós podemos concluir com os nossos resultados que a concentração e relação entre FCO2 e FO2 dependem dos diferentes sistemas e condições dos solos estudados, tais como: manejo de resíduos de culturas do solo, umidade do solo e uso de biochar. O FO2 está positivamente correlacionado com o FCO2 via atividade biológica e com valores de coeficientes respiratório (RQ) próximos de 1,0. Além disso, podemos observar que valores de RQ maiores que 1 são resultados dos fluxos de troca solo-gás após precipitação ou maior disponibilidade de O2 no meio. Assim, o FO2 pode ser utilizado como um índice para categorizar uma fonte de respiração de CO2. Para concluir, o biochar pode ser utilizado para sequestrar CO2 da atmosfera em curto período de tempo. No entanto, acreditamos que mais estudos devem ser desenvolvidos para elucidar a sorção de CO2 e O2 pelo biochar e suas reações (biológicas e/ou químicas) quando adicionado biochar no solo.
The soil O2 and CO2 concentration are the two most important gases related to soil microorganisms. Thus, this thesis was developed to observe the concentration and relationship between carbon dioxide (CO2) and oxygen (O2) under different residue systems. For that, we run two soil experiments in Brazil and the USA, respectively. The first experiment was developed to examine the relationship between CO2 and O2 using soil moisture and O2 as a soil respiration predictor in a sugarcane area under different managements of residues (mechanical harvesting - GH versus straw burning - BH). Therefore, the first experimental results are described in the Chapter 2 and entitled “Use of O2 uptake as an index of CO2 respiration in sugarcane areas under different managements”. We run the second soil experiment measuring biochar’s impact on CO2 production or sorption and O2 uptake in amended soils. Thus, we studied three soil types (Rosemount - RM; Potting soil Sunshine - PS; and UM) and five different biochars (Pine chip biochar - ICM; Royal Oak hardwood lump charcoal - RO; Accurel activated charcoal - AAC; Bamboo - B; and Macadamia nut - MC) and control treatment (Soil without biochar). Consequently, the results are described in the Chapter 3 and entitled “How O2 uptake can help us understand the CO2 sorption processes by biochar?”. Thus, we can conclude with our results that the concentration and relationship between FCO2 and FO2 depend on different systems and soil conditions, for example: soil crop residue managements, soil moisture and use of biochar. The FO2 is positively correlated with FCO2 at biological condition with respiratory quotient (RQ) values close to 1.0. Moreover, we can observe that RQ values higher than 1 are results of soil–gas exchange fluxes after precipitation or higher available on O2. Thus, the FO2 can be used as an index for categorizing the source of FCO2 respiration. To finish, we can observe that the biochar can be used to sequester CO2 from the atmosphere by the absence of biological activities in a short period of time. However, we believe that more study should be developed to elucidate the CO2 and O2 sorption by biochars and their reactions (biological and/or chemical) when added biochar in soil.
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Ping, Zhang. « The partitioning of water loss between crop transpiration and soil evaporation in potato crops ». Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303926.
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Granchie, Robert C. « Distribution of Partitioning of Lead Related to Soil Characteristics in a Former Gun Range ». Youngstown State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1464795738.
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Murphy, Meaghan Thibault. « Biotic and abiotic controls on soil respiration in a biodiversity plantation in the tropics ». Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97978.
Texte intégralRésumé :
The Sardinilla plantation is a long-term facility for studying the links between tree species diversity and ecosystem function. Six native tree species were planted in 2001 in plots containing 1, 3 or 6 species. Soil respiration (SR) measurements were conducted from March to December 2004 on tree pairs. ANOVAs with repeated measure on days were used to test the main effects of species (monocultures), pair (single and two-species pairs), plot (pairs in monoculture, three-, and six-species plots), and season (dry vs. early wet season). ANCOVAs were run for each effect to determine possible biotic and abiotic covariates, including root, tree, and microbial biomass, soil moisture, surface temperature, and bulk density. Significant season and pair effects accounted for 89% and 2% of the variability in SR. Driven by soil moisture, SR increased seven fold during the seasonal transition. In the dry and wet season monocultures had significantly higher SR than two-species pairs.