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Title: Links between above and belowground communities : tree-driven impacts on food webs and ecosystem processes
Author: Keith, Aidan Marischal
ISNI:       0000 0001 3596 4297
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2007
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Examining mechanistic links between above and belowground communities IS important to understand how land-use change may influence belowground food webs and ecosystem processes. Native woodland expansion is encouraged by conservation policy in the United Kingdom, but consequences of tree regeneration for belowground communities are poorly understood. This thesis examined mechanisms by which the plant community may control nematode community structure, and decomposition. In a correlative field study, changes in plant community structure were related to changes in nematode abundance, trophiq''structure and diversity, indicating treedriven impacts on litter inputs may determine belowground community structure. Increased nematode abundance and prevalence of higher trophic levels (Le. predators) were associated with more productive plant communities, and nematode diversity was positively related to plant diversity. A manipulative field experiment established that plant litter diversity generally had limited effects on the decomposer system, while plant litter identity had strong effects on decomposition, microbial biomas~ and the abundance of different nematode trophic groups. Collectively, these data demonstrate that plant species composition is more important than plant species diversity in determining belowground community structure and ecosystem processes. A mesocosm experiment tested the relative importance of above and belowground tree inputs on belowground community structure and decomposition. Litter addition, even at unnaturally high levels, had limited effects on the soil nematode community, whereas the presence of tree roots markedly altered nematode abundance and trophic structure, and microbial biomass. Changes in nematode community structure, particularly increases in predatory nematode abundance, in the presence of roots, indicate that belowground tree inputs may be more important than aboveground litter inputs in determining soil food web structure and complexity. This thesis established that trees can have a considerable impact on belowground community structure and ecosystem processes by controlling detrital inputs, both directly, and indirectly via changes in plant community composition. Consequently, it has demonstrated how land-use change may influence the belowground system, and thus improved our understanding of mechanisms by which above and belowground communities are linked.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available