Professor Davey Jones
Professor of Soil and Environmental Science / Associate Pro Vice-Chancellor
![](https://research.bangor.ac.uk/portal/files/55719909/DaveyJones_camera.jpg)
Dolenni cyswllt
Contact info
Address: Environment Centre Wales, Bangor University, Bangor, Gwynedd, LL57 2UW
Email: d.jones@bangor.ac.uk
Tel: 07827 807516 (UK) and 00 44 1248 382579 (International)
Researchgate profile; Google scholar profile; Twitter feed; Web of Science ResearcherID: C-7411-2011
- 2021
- Cyhoeddwyd
Microbial potential for denitrification in the hyperarid Atacama Desert soils
Wu, D., Senbayram, M., Moradi, G., Moerchen, R., Knief, C., Klumpp, E., Jones, D. L., Well, R., Chen, R. & Bol, R., 1 Meh 2021, Yn: Soil Biology and Biochemistry. 157, 108248.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Root hairs and protein addition to soil promote leucine aminopeptidase activity of Hordeum vulgare L
Greenfield, L., Razavi, B., Bilyera, N., Zhang, X. & Jones, D. L., 1 Meh 2021, Yn: Rhizosphere. 18, 100329.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Within-field spatial variability of greenhouse gas fluxes from an extensive and intensive sheep-grazed pasture
Charteris, A. F., Harris, P., Marsden, K. A., Harris, I. M., Guo, Z., Beaumont, D. A., Taylor, H., Sanfratello, G., Jones, D. L., Johnson, S. C. M., Whelan, M. J., Howden, N., Sint, H., Chadwick, D. R. & Cardenas, L. M., 1 Meh 2021, Yn: Agriculture, Ecosystems and Environment. 312, 107355.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Investigating awareness, fear and control associated with norovirus and other pathogens and pollutants using best–worst scaling
Farkas, K., Green, E., Rigby, D., Cross, P., Tyrrel, S., Malham, S. & Jones, D. L., 27 Mai 2021, Yn: Scientific Reports. 11, 1, 11 t., 11194.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Overriding water table control on managed peatland greenhouse gas emissions
Evans, C. D., Peacock, M., Baird, A. J., Artz, R. R. E., Burden, A., Callaghan, N., Chapman, P. J., Cooper, H. M., Coyle, M., Craig, E., Cumming, A., Dixon, S., Gauci, V., Grayson, R. P., Helfter, C., Heppell, C. M., Holden, J., Jones, D. L., Kaduk, J., Levy, P., Matthews, R., McNamara, N. P., Misselbrook, T., Oakley, S., Page, S. E., Rayment, M., Ridley, L., Stanley, K. M., Williamson, J. L., Worrall, F. & Morrison, R., 27 Mai 2021, Yn: Nature. 593, t. 548-552Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Volatile organic compounds (VOCs) allow sensitive differentiation of biological soil quality
Brown, R., Ian D. Bull, Toby Journeaux, Chadwick, D. & Jones, D. L., 1 Mai 2021, Yn: Soil Biology and Biochemistry. 156, 108187.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
The microplastisphere: biodegradable microplastics addition alters soil microbial community structure and function
Zhou, J., Gui, H., Banfield, C., Wen, Y., Dippold, M. A., Charlton, A. & Jones, D. L., Mai 2021, Yn: Soil Biology and Biochemistry. 156, 108211.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Arbuscular mycorrhizal fungi and biochar influence simazine decomposition and leaching
Cheng, H., Wang, J., Tu, C., Lin, S., Xing, D., Hill, P., Chadwick, D. & Jones, D. L., 1 Ebr 2021, Yn: Global Change Biology Bioenergy. 13, 4, t. 708-718Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Organic mulching masks rhizosphere effects on carbon and nitrogen fractions and enzyme activities in urban greening space
Sun, X., Ye, Y., Guan, Q. & Jones, D. L., 1 Ebr 2021, Yn: Journal of Soils and Sediments. 21, 4, t. 1621-1632Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Quantifying citrate-enhanced phosphate root uptake using microdialysis
McKay Fletcher, D. M., Shaw, R., Sanchez-Rodriguez, A. R., Daly, K. R., van Veelen, A., Jones, D. L. & Roose, T., Ebr 2021, Yn: Plant and Soil. 461, 1-2, t. 69-89 21 t.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Reintegration Of Crop-Livestock Systems In Europe : An Overview
Schut, A. G. T., Cooledge, E., Moraine, M., van de Ven, G. W. J., Jones, D. L. & Chadwick, D., Maw 2021, Yn: Frontiers of Agricultural Science and Engineering. 8, 1, t. 111-129 18 t.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Concentration and quantification of SARS-CoV-2 RNA in wastewater using polyethylene glycol-based concentration and qRT-PCR
Farkas, K., Hillary, L., Thorpe, J., Walker, D., Lowther, J. A., McDonald, J., Malham, S. & Jones, D. L., 23 Chwef 2021, Yn: Methods and Protocols. 4, 1, 10 t., 17.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
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Precipitation-optimised targeting of nitrogen fertilisers in a model maize cropping system
McKay Fletcher, D. M., Ruiz, S. A., Dias, T., Chadwick, D. R., Jones, D. L. & Roose, T., 20 Chwef 2021, Yn: Science of the Total Environment. 756, 144051.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
E. coli Is a Poor End-Product Criterion for Assessing the General Microbial Risk Posed From Consuming Norovirus Contaminated Shellfish
Sharp, J. H., Clements, K., Diggens, M., McDonald, J. E., Malham, S. K. & Jones, D. L., 19 Chwef 2021, Yn: Frontiers in Microbiology. 12, t. 608888Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Utilization of low-molecular-weight organic compounds by the filterable fraction of a lotic microbiome
Ghuneim, L. A., Distaso, M., Chernikova, T., Bargiela, R., Lunev, E. A., Korzhenkov, A. A., Toshchakov, S. V., Rojo, D., Barbas, C., Ferrer, M., Golyshina, O., Golyshin, P. & Jones, D. L., 1 Chwef 2021, Yn: Fems Microbiology Ecology. 97, 2Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Abiotic and biotic controls of soil dissolved organic nitrogen along a precipitation gradient on the Tibetan plateau
Jiang, L., Wang, S., Pang, Z., Wang, C., Meng, F., Lan, Z., Zhou, X., Li, Y., Zhang, Z., Luo, C., Jones, D. L., Rui, Y. & Wang, Y., Chwef 2021, Yn: Plant and Soil. 459, 1-2, t. 65-78Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Land use effects on soil phosphorus behavior characteristics in the eutrophic aquatic-terrestrial ecotone of Dianchi Lake, China
Fu, D., Xu, Z., Wu, X., Zhao, L., Zhu, A., Duan, C., Chadwick, D. R. & Jones, D. L., 31 Ion 2021, Yn: Soil & Tillage Research. 205, 104793.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Field test on the biodegradation of poly(butylene adipate-co-terephthalate) based mulch films in soil
Qi, R., Jones, D. L., Liu, Q., Liu, Q., Li, Z. & Yan, C., Ion 2021, Yn: Polymer testing . 93, 107009.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Spatial co‐localisation of extreme weather events: a clear and present danger
Dodd, R., Chadwick, D., Harris, I., Hines, A., Hollis, D., Economou, T., Gwynn-Jones, D., Scullion, J., Robinson, D. & Jones, D. L., Ion 2021, Yn: Ecology Letters. 24, 1, t. 60-72 13 t.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Innovations in soil science to address global grand challenges
Haygarth, P. M., Kirk, G. J. D. & Jones, D. L., 2021, Yn: European Journal of Soil Science. 72, 6, t. 2317-2319 3 t.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Golygyddiad › adolygiad gan gymheiriaid
- 2020
- Cyhoeddwyd
Combining Seed Dressing and Foliar Applications of Phosphorus Fertilizer Can Give Similar Crop Growth and Yield Benefits to Soil Applications Together With Greater Recovery Rates
Talboys, P., Healey, J., Withers, P., Roose, T., Edwards, A., Pavinato, P. S. & Jones, D. L., 4 Rhag 2020, Yn: Frontiers in Agronomy. 2, 10.3389/fagro.2020.605655 .Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Acidification and anaerobic digestion change the phosphorus forms and distribution in particle fractions of cattle slurry and phosphorus dynamics in soil after application
Li, Y., Chen, Q., Ge, T., Chadwick, D. R. & Jones, D. L., 1 Rhag 2020, Yn: Biosystems Engineering. 200, t. 101-111Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
High representation of archaea across all depths in oxic and low-pH sediment layers underlying an acidic stream
Distaso, M., Bargiela, R., Brailsford, F., Williams, G., Wright, S., Lunev, E. A., Toshchakov, S. V., Yakimov, M. M., Jones, D. L., Golyshin, P. & Golyshina, O., 17 Tach 2020, Yn: Frontiers in Microbiology. 11, t. 576520Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Polyphenolic Profiling of Forestry Waste by UPLC-HDMSE
Potter, C. M. & Jones, D. L., 4 Tach 2020, Yn: Processes. 8Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Carbon and sulphur tracing from soil organic sulphur in plants and soil microorganisms
Ma, Q., Luo, Y., Wen, Y., Hill, P. W., Chadwick, D. R., Wu, L. & Jones, D. L., 1 Tach 2020, Yn: Soil Biology and Biochemistry. 150, 107971.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Is soluble protein mineralisation and protease activity in soil regulated by supply or demand?
Greenfield, L. M., Hill, P. W., Seaton, F. M., Paterson, E., Baggs, E. M. & Jones, D. L., 1 Tach 2020, Yn: Soil Biology and Biochemistry. 150, 108007.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Making waves: Wastewater-based epidemiology for COVID-19-approaches and challenges for surveillance and prediction
Polo, D., Quintela-Baluja, M., Corbishley, A., Jones, D. L., Singer, A. C., Graham, D. W. & Romalde, J. L., 1 Tach 2020, Yn: Water Research. 186, 116404.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Do plants use root-derived proteases to promote the uptake of soil organic nitrogen?
Greenfield, L. M., Hill, P. W., Paterson, E., Baggs, E. M. & Jones, D. L., Tach 2020, Yn: Plant and Soil. 456, 1-2, t. 355-367Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Impact of Sediment Concentration on the Survival of Wastewater-Derived blaCTX-M-15-Producing E. coli, and the Implications for Dispersal into Estuarine Waters
Bashawri, Y. M. A., Robins, P., Jones, D. L., McDonald, J., Cooper, D. & Williams, P., 19 Hyd 2020, Yn: International Journal of Environmental Research and Public Health. 17, 20, 15 t., 7608.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Sheep urination frequency, volume, N excretion and chemical composition: Implications for subsequent agricultural N losses
Marsden, K. A., Lush, L., Holmberg, J. A., Whelan, M. J., King, A. J., Wilson, R. P., Charteris, A. F., Cardenas, L. M., Jones, D. L. & Chadwick, D. R., 15 Hyd 2020, Yn: Agriculture, Ecosystems and Environment. 302, 107073.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Synthesis and characterization of struvite derived from poultry manure as a mineral fertilizer
Rech, I., Kamogawa, M. Y., Jones, D. L. & Pavinato, P. S., 15 Hyd 2020, Yn: Journal of Environmental Management. 272, 111072.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Long-term farmyard manure application affects soil organic phosphorus cycling: A combined metagenomic and P-33/C-14 labelling study
Ma, Q., Wen, Y., Ma, J., Macdonald, A., Hill, P. W., Chadwick, D. R., Wu, L. & Jones, D. L., 1 Hyd 2020, Yn: Soil Biology and Biochemistry. 149, 107959.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Response of soil phosphorus fractions and fluxes to different vegetation restoration types in a subtropical mountain ecosystem
Fu, D., Wu, X., Duan, C., Chadwick, D. R. & Jones, D. L., 1 Hyd 2020, Yn: Catena. 193, 104663.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Soil carbon, nitrogen, and sulphur status affects the metabolism of organic S but not its uptake by microorganisms
Ma, Q., Wen, Y., Pan, W., Macdonald, A., Hill, P. W., Chadwick, D. R., Wu, L. & Jones, D. L., 1 Hyd 2020, Yn: Soil Biology and Biochemistry. 149, 107943.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Seasonality is more important than forest type in regulating the pool size and composition of soil soluble N in temperate forests
Gao, L., Hill, P. W., Jones, D. L., Guo, Y., Gao, F. & Cui, X., Hyd 2020, Yn: Biogeochemistry. 150, 3, t. 279-295Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Wastewater and public health: the potential of wastewater surveillance for monitoring COVID-19
Farkas, K., Hillary, L., Malham, S., McDonald, J. & Jones, D. L., Hyd 2020, Yn: Current Opinion in Environmental Science & Health. 17, t. 14-20 7 t.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Revealing soil legacy phosphorus to promote sustainable agriculture in Brazil
Pavinato, P. S., Cherubin, M. R., Soltangheisi, A., Rocha, G. C., Chadwick, D. R. & Jones, D. L., 28 Medi 2020, Yn: Scientific Reports. 10, 15615, 15615.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Impact of a single freeze-thaw and dry-wet event on soil solutes and microbial metabolites
Miura, M., Hill, P. W. & Jones, D. L., 1 Medi 2020, Yn: Applied Soil Ecology. 153, 103636.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Microplastics in the agroecosystem: Are they an emerging threat to the plant-soil system?
Zang, H., Zhou, J., Marshall, M. R., Chadwick, D. R., Wen, Y. & Jones, D. L., 1 Medi 2020, Yn: Soil Biology and Biochemistry. 148, 107926.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Seasonal variations in soil microbial communities under different land restoration types in a subtropical mountains region, Southwest China
Fu, D., Wu, X., Qiu, Q., Duan, C. & Jones, D. L., 1 Medi 2020, Yn: Applied Soil Ecology. 153, 103634.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Suppression of amino acid and oligopeptide mineralization by organic manure addition in a semiarid environment
Iqbal, S., Jones, D. L., Arif, M. S., Yasmeen, T., Xu, J., Khan, S. & Nadir, S., Medi 2020, Yn: Land Degradation and Development. 31, 15, t. 1915-1925 11 t.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Soil microbes of an urban remnant riparian zone have greater potential for N removal than a degraded riparian zone
Middleton, J. A., de Sosa, L. L., Martin, B. C., Jones, D. L. & Gleeson, D. B., 31 Awst 2020, Yn: Environmental Microbiology. 22, 8, t. 3302-3314Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Viral indicators for tracking domestic wastewater contamination in the aquatic environment
Farkas, K., Walker, D., Adriaenssens, E., McDonald, J., Hillary, L., Malham, S. & Jones, D. L., 15 Awst 2020, Yn: Water Research. 181, 115926.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Crop residue carbon-to-nitrogen ratio regulates denitrifier N2O production post flooding
Zhou, W., Jones, D. L., Hu, R., Clark, I. M. & Chadwick, D. R., Awst 2020, Yn: Biology and Fertility of Soils. 56, 6, t. 825-838Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Effects ofAgeratina adenophoraInvasion on the Understory Community and Soil Phosphorus Characteristics of Different Forest Types in Southwest China
Wu, X., Duan, C., Fu, D., Peng, P., Zhao, L. & Jones, D. L., 25 Gorff 2020, Yn: Forests. 11, 8Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Image-based quanti fication of soil microbial dead zones induced by nitrogen fertilization
Ruiz, S. A., Fletcher, D. M. M., Boghi, A., Williams, K. A., Duncan, S. J., Scotson, C. P., Petroselli, C., Dias, T. G. S., Chadwick, D. R., Jones, D. L. & Roose, T., 20 Gorff 2020, Yn: Science of the Total Environment. 727, 138197.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Raising the groundwater table in the non -growing season can reduce greenhouse gas emissions and maintain crop productivity in cultivated fen peats
Wen, Y., Freeman, B., Ma, Q., Evans, C. D., Chadwick, D. R., Zang, H. & Jones, D. L., 20 Gorff 2020, Yn: Journal of Cleaner Production. 262, 121179.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Wastewater-Based Epidemiology: Global Collaborative to Maximize Contributions in the Fight Against COVID-19
Bivins, A., North, D., Ahmad, A., Ahmed, W., Alm, E., Been, F., Bhattacharya, P., Bijlsma, L., Boehm, A. B., Brown, J., Buttiglieri, G., Calabro, V., Carducci, A., Castiglioni, S., Gurol, Z. C., Chakraborty, S., Costa, F., Curcio, S., de los Reyes, F. L. . III., Vela, J. D., Farkas, K., Fernandez-Casi, X., Gerba, C., Gerrity, D., Girones, R., Gonzalez, R., Haramoto, E., Harris, A., Holden, P. A., Islam, M. T., Jones, D. L., Kasprzyk-Hordern, B., Kitajima, M., Kotlarz, N., Kumar, M., Kuroda, K., La Rosa, G., Malpei, F., Mautus, M., McLellan, S. L., Medema, G., Meschke, J. S., Mueller, J., Newton, R. J., Nilsson, D., Noble, R. T., van Nuijs, A., Peccia, J., Perkins, T. A., Pickering, A. J., Rose, J., Sanchez, G., Smith, A., Stadler, L., Stauber, C., Thomas, K., van der Voorn, T., Wigginton, K., Zhu, K. & Bibby, K., 7 Gorff 2020, Yn: Environmental Science and Technology. 54, 13, t. 7754-7757Allbwn ymchwil: Cyfraniad at gyfnodolyn › Golygyddiad › adolygiad gan gymheiriaid
- Cyhoeddwyd
Ocean warming increases the nitrogen demand and the uptake of organic nitrogen of the globally distributed seagrass Zostera marina
Alexandre, A., Quinta, R., Hill, P., Jones, D. L. & Santos, R., Gorff 2020, Yn: Functional Ecology. 34, 7, t. 1325-1335 11 t.Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid
- Cyhoeddwyd
Traits of dominant species and soil properties co -regulate soil microbial communities across land restoration types in a subtropical plateau region of Southwest China
University, Y., China, K., Duan, C., Smith, A. R. & Jones, D. L., 15 Meh 2020, Yn: Ecological Engineering. 153Allbwn ymchwil: Cyfraniad at gyfnodolyn › Erthygl › adolygiad gan gymheiriaid