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25 results on '"Lloyd, Colin R."'

5. Net ecosystem exchange over heterogeneous Arctic tundra: Scaling between chamber and eddy covariance measurements

Author

Fox, Andrew M., Huntley, Brian, Lloyd, Colin R., Williams, Mathew, and Baxter, Robert

Subjects
DYNAMICS, Global and Planetary Change, Atmospheric Science, LANDSCAPE, MODELS, FOREST, CO2 FLUX, ECOTONE, CARBON-DIOXIDE, RESPIRATION, Environmental Science(all), CANOPY, Environmental Chemistry, FOOTPRINTS
Abstract

Net ecosystem exchange (NEE) was estimated for an area of tundra near Abisko using both eddy covariance (EC) data and chamber measurements. This area of tundra is heterogeneous with six principal elements forming a landscape mosaic. Chamber measurements in patches of the individual mosaic elements were used to model NEE as a function of irradiance and temperature. The area around the EC mast was mapped, and a footprint model was used to simulate the varying source fraction attributable to each mosaic element. Various upscaling approaches were used to estimate NEE for comparison with NEE calculated from the EC observations. The results showed that EC measurements made for such a heterogeneous site are robust to the variations in NEE between mosaic elements that also vary substantially in their source fractions. However, they also revealed a large (similar to 60%) bias in the absolute magnitude of the cumulative negative NEE for a 40-day study period simulated by various upscaling approaches when compared to the value calculated from the EC observations. The magnitude of this bias, if applied to estimates for the entire tundra region, is substantial in relation to other components of the global carbon budget. Various hypotheses to account for this bias are discussed and, where possible, evaluated. A need is identified for more systematic sampling strategies when performing chamber measurements in order to assess the extent to which subjectivity of chamber location may account for much of the observed bias. If this is the origin of the bias, then upscaling approaches using chamber measurements may generally overestimate CO2 uptake.

Published
2008
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6. Providing low-budget estimations of carbon sequestration and greenhouse gas emissions in agricultural wetlands

Author

Lloyd, Colin R., Rebelo, Lisa-Maria, Finlayson, C. Max, Lloyd, Colin R., Rebelo, Lisa-Maria, and Finlayson, C. Max

Abstract

The conversion of wetlands to agriculture through drainage and flooding, and the burning of wetland areas for agriculture have important implications for greenhouse gas (GHG) production and changing carbon stocks. However, the estimation of net GHG changes from mitigation practices in agricultural wetlands is complex compared to dryland crops. Agricultural wetlands have more complicated carbon and nitrogen cycles with both above- and below-ground processes and export of carbon via vertical and horizontal movement of water through the wetland. This letter reviews current research methodologies in estimating greenhouse gas production and provides guidance on the provision of robust estimates of carbon sequestration and greenhouse gas emissions in agricultural wetlands through the use of low cost reliable and sustainable measurement, modelling and remote sensing applications. The guidance is highly applicable to, and aimed at, wetlands such as those in the tropics and sub-tropics, where complex research infrastructure may not exist, or agricultural wetlands located in remote regions, where frequent visits by monitoring scientists prove difficult. In conclusion, the proposed measurement-modelling approach provides guidance on an affordable solution for mitigation and for investigating the consequences of wetland agricultural practice on GHG production, ecological resilience and possible changes to agricultural yields, variety choice and farming practice.

Published
2013

9. Mailserver.

Author

Solomon, Rob, Mohr, Neil, Collins, Peter, Lloyd, Colin R, McDonald, Tony, Peters, Harry, and Paul

Published
2022

16. How do soil emissions of N2O, CH4 and CO2 from perennial bioenergy crops differ from arable annual crops?

Author

Drewer, Julia, Finch, Jon W., Lloyd, Colin R., Baggs, Elizabeth M., and Skiba, Ute

Subjects
NITROUS oxide, METHANE, CARBON dioxide, ENERGY crops, SOIL respiration, BIOMASS energy, MISCANTHUS, WILLOWS
Abstract

It is important to demonstrate that replacing fossil fuel with bioenergy crops can reduce the national greenhouse gas ( GHG) footprint. We compared field emissions of nitrous oxide (N2O), methane ( CH4) and soil respiration rates from the C4 grass Miscanthus × giganteus and willow ( salix) with emissions from annual arable crops grown for food production. The study was carried out in NE England on adjacent fields of willow , Miscanthus, wheat ( Triticum aetivum) and oilseed rape ( Brassica napus). N2O, CH4 fluxes and soil respiration rates were measured monthly using static chambers from June 2008 to November 2010. Net ecosystem exchange ( NEE) of carbon dioxide ( CO2) was measured by eddy covariance on Miscanthus from May 2008 and on willow from October 2009 until November 2010. The N2O fluxes were significantly smaller from the bioenergy crops than that of the annual crops. Average fluxes were 8 and 32 μg m−2 h−1 N2O-N from wheat and oilseed rape, and 4 and 0.2 μg m−2 h−1 N2O-N from Miscanthus and willow, respectively. Soil CH4 fluxes were negligible for all crops and soil respiration rates were similar for all crops. NEE of CO2 was larger for Miscanthus (−770 g C m−2 h−1) than willow (−602 g C m−2 h−1) in the growing season of 2010. N2O emissions from Miscanthus and willow were lower than for the wheat and oilseed rape which is most likely a result of regular fertilizer application and tillage in the annual arable cropping systems. Application of 15N-labelled fertilizer to Miscanthus and oil seed rape resulted in a fertilizer-induced increase in N2O emission in both crops. Denitrification rates (N2O + N2) were similar for soil under Miscanthus and oilseed rape. Thus, perennial bioenergy crops only emit less GHGs than annual crops when they receive no or very low rates of N fertilizer. [ABSTRACT FROM AUTHOR]

Published
2012
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18. Eddy correlation measurements of energy partition for Amazonian forest.

Author

Shuttleworth, W. James, Gash, John H. C., Lloyd, Colin R., Moore, Christopher J., Roberts, John, Filho, Ari De O. Marques, Fisch, Gilberto, De Paula Silva Filho, Vicente, Ribeiro, Maria De Nazaré Góes, Molion, Luiz C. B., De Abreu Sá, Leonardo D., Nobre, J. Carlos A., Cabral, Osvaldo M. R., Patel, Sukaran R., and Carvalho De Moraes, J.

Published
1984
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19. LETTERS.

Author

Brindle, Ron, Lloyd, Colin R., Fearnley, Barry, Mansfield, Mike, Holden, Warwick, and Parker, Jason

Published
2019

20. LETTERS.

Author

Tanser, Wilf, Salisbury, Jonathan, Lloyd, Colin R., Simpson, Colin, Jepson, Chris, Robinson, Gordon, and Tegan

Published
2019

21. LETTERS.

Author

Deketelaere, Paul, Lloyd, Colin R., Fearnley, Barry, Lewis, Steven, and Walker, Mike

Published
2019

22. LETTERS.

Author

Murray, Robert, Tegan, Scott, Tony 'Bodger', John, Richard, Davy, Phil, Peachey, John, Lloyd, Colin R., and Underwood, Graham

Published
2019

23. LETTERS.

Author

Greaves, Tom, Lloyd, Colin R., Tegan, and Watson, Gordon

Published
2018

24. Letters.

Author

Newman, Jeremy, Durbin, Maurice, Lloyd, Colin R., Peacock, Jennifer, McDaid, Simon, Saunders, Frank, Thorne, Angela, Walton, Eric, Westwood, Ken, and Stannard, Ian

Subjects
MICROSOFT Windows (Operating system), BT Group PLC, FRIENDS Reunited Ltd.
Abstract

Several letters to the editor are presented in response to articles in previous issues, including "Uninstall Windows 10 Apps Now," by Jonathan Parkyn, "Is BT Treating the British Public Like Fools?," and another letter on the closure of the web site Friends Reunited.

Published
2016

25. Letters.

Author

Moulds, Geoff, Nitikin, Igor, Cray, Colin, Scoote, John, Smith, Matthew, McFadyen, Stuart, Cambrill, Harold, Lloyd, Colin R, Davies, Paul, and Mitchell, Chris

Subjects
COMPUTER security, CAMERAS
Abstract

Several letters to the editor are presented in response to articles in previous issues about the view of Beatrice Southall over security services, the "Web scams are bad, but at least we don't live in Russia" by Raymond Daniels and the camera manuals of Nikon Corp.

Published
2014

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