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dc.contributor.advisorGriffiths, Bryan
dc.contributor.advisorDaniell, Tim
dc.contributor.advisorNeilson, Roy
dc.contributor.advisorO'Flaherty, Vincent
dc.contributor.authorChen, Xiaoyun
dc.description.abstractAlthough nematode community analysis is considered to be a useful environmental indicator, a major impediment to its wider adoption is the need for detailed morphological identification. Molecular techniques offer an alternative to this time-consuming traditional way. With both directed molecular T-RFLP approach and traditional microscopy for nematode analysis, this study characterized the responses of belowground nematode diversity and other associated soil processes to P fertilization in a long-term grassland trial and to inorganic N and cattle slurry application in short-term grassland plot. P fertilization (> 40 years) increased the proportion of bacterial-feeding nematodes, while decreased that of fungal-feeding nematodes, indicating a shift from fungal to bacterial pathways in more intensively managed systems. In addition, the microbial PLFA profiles confirmed fungal biomass and fungal-bacterial ratio decreased, but soil microbial biomass C, N and P increased, with P fertilization. Over the short-term period trial (< 2 years), nematode abundance increased significantly with slurry application, but not with inorganic N application. Inorganic N significantly increased bacterial-feeding nematodes, and decreased omnivorous ones, while slurry had no effects. Compared with slurry, higher inorganic N increased the herbage production and enhanced N uptake, indicating a faster N flux following inorganic N fertilization. The traditional and molecular techniques yielded comparable results on profiling nematode community. The rapid, easy and replicable T-RFLP approach was suitable for the routine monitoring of the soil nematode community, which helped to advance the characterization of soil biodiversity and monitoring the soil quality. Further, real-time PCR assessment was used to determine the correlation between SSU rDNA copy number and body size of four free-living nematode species. No correlation was found for Caenorhabditis elegans, showing it is eutelic. The three other species (Panagrolaimus detritophagus, Anatonchus tridentatus and Aporcelaimellus obtusicaudatu, however, are non-eutelic, showing that rDNA copy number increased significantly with body size.en_US
dc.subjectSoil nematodeen_US
dc.subjectSoil indicatoren_US
dc.subjectNematode morphologyen_US
dc.subjectMolecular methodsen_US
dc.subjectNatural Scienceen_US
dc.titleNematode response to nitrogen and phosphorus in grasslands, assessed by microscopy and molecular methodsen_US
dc.contributor.funderChen was supported by a Teagasc Walsh Fellowship (2008023)en_US
dc.local.noteThis thesis focused on the effects of grassland management on the soil nematode community and used soil nematodes as an indicator. The aim was to improve the understanding of soil biodiversity and led to a better management of grassland. The study also evaluated a high-throughput method for nematode community analysis, directed T-RFLP, for use as a potential bioindicator.en_US

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