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221 results on '"Baldock, J."'

4. Measurement of soil carbon oxidation state and oxidative ratio by 13 C nuclear magnetic resonance

Author

Hockaday, W. C, Masiello, C. A, Randerson, J. T, Smernik, R. J, Baldock, J. A, Chadwick, O. A, and Harden, J. W

Subjects
carbon balance, carbon budget, decomposition, measurement method, mode water, net ecosystem exchange, nuclear magnetic resonance, oxidation, photosynthesis, respiration, soil carbon, uncertainty analysis
Abstract

The oxidative ratio (OR) of the net ecosystem carbon balance is the ratio of net O2 and CO2 fluxes resulting from photosynthesis, respiration, decomposition, and other lateral and vertical carbon flows. The OR of the terrestrial biosphere must be well characterized to accurately estimate the terrestrial CO2 sink using atmospheric measurements of changing O2 and CO2 levels. To estimate the OR of the terrestrial biosphere, measurements are needed of changes in the OR of aboveground and belowground carbon pools associated with decadal timescale disturbances (e.g., land use change and fire). The OR of aboveground pools can be measured using conventional approaches including elemental analysis. However, measuring the OR of soil carbon pools is technically challenging, and few soil OR data are available. In this paper we test three solid-state nuclear magnetic resonance (NMR) techniques for measuring soil OR, all based on measurements of the closely related parameter, organic carbon oxidation state (Cox). Two of the three techniques make use of a molecular mixing model which converts NMR spectra into concentrations of a standard suite of biological molecules of known Cox. The third technique assigns Cox values to each peak in the NMR spectrum. We assess error associated with each technique using pure chemical compounds and plant biomass standards whose Cox and OR values can be directly measured by elemental analyses. The most accurate technique, direct polarization solid-state 13C NMR with the molecular mixing model, agrees with elemental analyses to ±0.036 Cox units (±0.009 OR units). Using this technique, we show a large natural variability in soil Cox and OR values. Soil Cox values have a mean of −0.26 and a range from −0.45 to 0.30, corresponding to OR values of 1.08 ± 0.06 and a range from 0.96 to 1.22. We also estimate the OR of the carbon flux from a boreal forest fire. Analysis of soils from nearby intact soil profiles imply that soil carbon losses associated with the fire had an OR of 1.091 (±0.003). Fire appears to be a major factor driving the soil C pool to higher oxidation states and lower OR values. Episodic fluxes caused by disturbances like fire may have substantially different ORs from ecosystem respiration fluxes and therefore should be better quantified to reduce uncertainties associated with our understanding of the global atmospheric carbon budget.

Published
2009

29. Sediment anoxia limits microbial-driven seagrass carbon remineralization under warming conditions

Author

Trevathan-Tackett, SM, Seymour, JR, Nielsen, DA, Macreadie, PI, Jeffries, TC, Sanderman, J, Baldock, J, Howes, JM, Steven, ADL, and Ralph, PJ

Subjects
Geologic Sediments, Carbon Sequestration, Hot Temperature, Alismatales, Eutrophication, Microbiology, Carbon, Oxygen, RNA, Ribosomal, 16S, Proteobacteria, Seawater, Biomass, Anaerobiosis, Ecosystem
Abstract

© FEMS 2017. All rights reserved. Seagrass ecosystems are significant carbon sinks, and their resident microbial communities ultimately determine the quantity and quality of carbon sequestered. However, environmental perturbations have been predicted to affect microbial-driven seagrass decomposition and subsequent carbon sequestration. Utilizing techniques including 16S-rDNA sequencing, solid-state NMR and microsensor profiling, we tested the hypothesis that elevated seawater temperatures and eutrophication enhance the microbial decomposition of seagrass leaf detritus and rhizome/root tissues. Nutrient additions had a negligible effect on seagrass decomposition, indicating an absence of nutrient limitation. Elevated temperatures caused a 19% higher biomass loss for aerobically decaying leaf detritus, coinciding with changes in bacterial community structure and enhanced lignocellulose degradation. Although, community shifts and lignocellulose degradation were also observed for rhizome/root decomposition, anaerobic decay was unaffected by temperature. These observations suggest that oxygen availability constrains the stimulatory effects of temperature increases on bacterial carbon remineralization, possibly through differential temperature effects on bacterial functional groups, including putative aerobic heterotrophs (e.g. Erythrobacteraceae, Hyphomicrobiaceae) and sulfate reducers (e.g. Desulfobacteraceae). Consequently, under elevated seawater temperatures, carbon accumulation rates may diminish due to higher remineralization rates at the sediment surface. Nonetheless, the anoxic conditions ubiquitous to seagrass sediments can provide a degree of carbon protection under warming seawater temperatures.

Published
2017

33. Carbon sequestration by Australian tidal marshes

Author

Macreadie, Peter I., primary, Ollivier, Q. R., additional, Kelleway, J. J., additional, Serrano, O., additional, Carnell, P. E., additional, Ewers Lewis, C. J., additional, Atwood, T. B., additional, Sanderman, J., additional, Baldock, J., additional, Connolly, R. M., additional, Duarte, C. M., additional, Lavery, P. S., additional, Steven, A., additional, and Lovelock, C. E., additional

Published
2017
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35. Abstracts of papers presented at the 63rd annual PAA meeting

Author

Rueda, Jose L., Berrios, Donald, Amoros W. R., Mendoza, H. A., Archuleta Jose Gil, Easton, Gene D., Brown C. R., Bruce Doug, Camadro Elsa, Peloquin, S. J., Davis J. R., Jones, W. B., Dearborn Curtis H., Deboer S. H., Dwelle Robert B., Kleinkopf, Gale E., Steinhorst, R. K., Pavek, J. J., Easton Gene D., Estrada Nelson, Ewing Elmer E., Hedges, Anne, Sieczka, Joseph B., Freeman Jack A., Goth R. W., Webb, R. E., Graham D. C., Hammond David F., Zozimo, Hauman, Henninger M. R., Patterson, J. W., Hiller L. K., Koller, D. C., VanDenburgh, R. W., Huang Don Y., Ryan, Clarence A., Swanson, Barry G., Hyde Gary M., Thornton, R. E., Kunkel, Robert, Iwanaga Masaru, Jackson Michael T., Gonzalez, L. C., Jaworski C. A., Goth, R. W., Phatak, S. C., Arthur, Kelman, Kintner Judy, Kloepper J. W., Schroth, M. N., Weinhold, A. R., Bowman, T., Kuenemann Ray, Kunkel R., Holstad, N. M., Mitchell, D. C., Russell, T. S., Landeo J. A., Hanneman, R. E., Lazin M. B., Mendoza, Humberto A., Sung, I. J., Ewing, E. E., Sieczka, J. B., Levy David, Martin Mark W., McLaughlin Richard, Munoz F. J., Plaisted, R. L., Ng K. C., Weaver, M. L., Nielsen, L. W., O’keefe R. B., Osman S. F., Zacharius, R. M., Otazu V., Zink, R. T., Secor, Gary A., Rasco Eufemio T., Plaisted, Robert L., Reeves A. F., Hunter, J. H., Ross Craig, Kunkel, R., Gardner, W., Rowe R. C., Sacher R. F., Iritani, W. M., Sand Paul, Aphis, F., Sanford L. L., Ladd, T. L., Sinden S. L., Sanford, L. L., Osman, S. F., Steven, Slack, Slack S. A., Sanford, H. A., Manzer, F. E., Sparks Walter C., Stiles Dwight G., Tai G. C. C., Tarn, T. R., Tarhan A. F., Cash, J. N., Markakis, P., Thornton Robert E., Vandenburgh R. W., Hiller, L. K., Vitosh M. L., Bird, G. W., Chase, R. W., Noling, J. W., Vruggink H., Geesteranus, Maas, H. P., Weaver M. L., Ng, K. C., Weis G. G., Wade, E. K., Baldock, J. O., Wells Arthur L., Workman Milton, Cameron, Arthur, Twomey, James, Yu Wen-Wei, Swanson, B. G., and Zink R. T.

Published
1979
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37. Voluntary Screening Program for Prostate Cancer: Detection Rate and Cost

Author

Abramson N, Baldock J, Cotton S, and Eckels R

Subjects
Male, Oncology, medicine.medical_specialty, Cost estimate, Biopsy, Treatment outcome, Prostate cancer, Internal medicine, medicine, Humans, Mass Screening, Initial therapy, Physical Examination, health care economics and organizations, Aged, medicine.diagnostic_test, business.industry, Carcinoma, Prostatic Neoplasms, Reproducibility of Results, Cancer, Health Care Costs, General Medicine, Rectal examination, Middle Aged, Prostate-Specific Antigen, medicine.disease, Emergency medicine, Costs and Cost Analysis, Florida, Antigen measurement, Detection rate, business
Abstract

In a community-wide screening program conducted in Jacksonville, Florida, 564 participants received free screening for prostate cancer. Frequency of positive results of prostate-specific antigen measurement and digital rectal examination was comparable to that found in similar programs in other communities. The estimated cost for each participant was $231, and the cost to discover each cancer was $7,240. If one also includes initial therapy in cost estimates, then the cost per participant was $520, and the cost to find and treat each patient was $16,300. The value of screening for prostate cancer must be judged by treatment outcome and underlying costs.

Published
1994

45. Families, work and social care in Europe. A qualitative study of care arrangements in Finland, France, Italy, Portugal and the UK

Author

São José, José, Sipilä, Jorma, Repo, Katja, Zechnner, Minna, Martin, Claude, Debroise, A., Le Bihan, B., Wall, Karin, Correia, Sónia, Baldock, J., Hadlow, Jan, Vion, A., Larsen, Trine, and Kröger, Teppo

Subjects
Social care, Reconciliation of work, Family life
Abstract

The SOCCARE Project studied social care arrangements of European families in five different socio-economic and cultural environments that represent the variety of European welfare states (Finland, France, Italy, Portugal and the UK). It focused on four key family types that all are heavily affected by the ongoing demographic, socio-economic and structural changes within European societies: 1) lone parent families, 2) dual-career families, 3) immigrant families and, 4) “double front carer” families (that have young children and, at the same time, elderly family members in need of care). European Commission, 5th Framework Programme; SOCCARE Project

Published
2003

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