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dc.contributor.advisorSubke, Jens-Arne-
dc.contributor.advisorQuilliam, Richard S-
dc.contributor.authorJackson, Oyindamola Ibitola-
dc.description.abstractRising atmospheric CO2 concentration may increase plant productivity through the “CO2 fertilization effect”, which may in turn increase the input of carbon (C) to soils through rhizodeposition or plant residues. However, whether this increase in C input to soils results in greater soil C storage is not clear, as the decomposition of different forms of organic matter and the role of the rhizosphere in the decomposition process remain poorly understood. In this thesis, I investigated the interactions between plant C dynamics and soil microbial processes, and how these interactions control C and nutrient cycling in forest soils. I manipulated soil carbon supply from trees to the rhizosphere both in mesocosms and in the field through either canopy shading or soil trenching. This allowed me to investigate the effect of assimilate C supply on the decomposition of 13C-labelled substrates of varying chemical compositions and structural complexities (glucose, straw, fungal necromass or biochar), and their combined effect on soil organic matter (SOM) decomposition. I found that plant C supply to the rhizosphere had no significant effect on the decomposition of substrates. Similarly, the presence of roots and their associated mycorrhizal fungi had no significant effect on litter mass loss. However, it was found that supply of C from plant to the rhizosphere promoted SOM decomposition by up to two-fold in soils amended with substrates. Although, the addition of both simple and complex substrates stimulated the activities of C, N and P- degrading enzymes, I observed that the activities of these enzymes were significantly greater in soils where a labile substrate (glucose) had been added. The increased activities of C-degrading enzymes suggest that microorganisms were C limited, and the input of labile C substrate alleviated C and energy limitation of enzyme production, allowing microbial communities to mobilize nutrients from decomposition of native SOM. This thesis demonstrates that substrate quality influences SOM decomposition, and that increased availability of labile substrates to the rhizosphere may have implications on forest soil C stocks.en_GB
dc.publisherUniversity of Stirlingen_GB
dc.subjectSoil organic matteren_GB
dc.subjectStable Isotopeen_GB
dc.subjectPriming effecten_GB
dc.subjectPlant-soil interactionen_GB
dc.subject.lcshSoil microbiologyen_GB
dc.subject.lcshSoil and the environmenten_GB
dc.subject.lcshPlant-soil relationships.en_GB
dc.subject.lcshPlant physiologyen_GB
dc.subject.lcshForest soilsen_GB
dc.titleInvestigating Rhizosphere Controls of Soil Organic Matter Dynamics in Forest Soils using a 13C Labelling Approachen_GB
dc.typeThesis or Dissertationen_GB
dc.type.qualificationnameDoctor of Philosophyen_GB
dc.rights.embargoreasonI am in the process of publishing one of the chapters in a journal.en_GB
Appears in Collections:Biological and Environmental Sciences eTheses

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