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Title: Phosphorus (P) partitioning among co-occurring plants : competition for P acquisition across different forms of P and through soil microbes
Author: Muddimer, Stephen
ISNI:       0000 0004 5993 2689
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2016
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Soils of low phosphorus (P) availability are found globally, and often have high plant species richness despite co-existing species competing for the same limited P resource. How diverse communities maintain co-existence despite limited access to this resource is poorly understood. This thesis investigated plant P acquisition in P-limited calcareous grasslands and the mechanisms which may sustain species coexistence in these plant communities. For this, a range of calcareous grassland species were used which varied in their methods of P acquisition. Using radiolabelled P-sources, it was shown that interspecific differences in P uptake by plants across a range of chemical P-forms were consistent with contrasting methods of P acquisition. Species with specialist rooting structures and high rates of root exudation acquired the greatest amounts of P from sources which require mobilisation before uptake. This included organic diesters (DNA) and inorganic mineral P (calcium phosphate). However, these species showed consistent reductions in P uptake in response to competition from mycorrhizal species, which maintained or increased P uptake. Comparisons of these competitive interactions in controlled systems showed that this competitive effect was determined by mycorrhizal status. P uptake by soil microbial communities growing under different plant species monocultures and mixed plant communities was measured from radiolabelled calcium phosphate. While there was some variation in microbial P uptake across plant species monocultures, this did not relate to differences in plant uptake. Microbial P uptake increased significantly in mixed plant communities compared to monocultures, highlighting the importance of species richness on mobilisation of P from calcium phosphate through microbial uptake. These findings provide a new perspective on ecological processes which sustain species richness in P-limited plant communities. Given the prevalence of Plimitation throughout terrestrial ecosystems, this could have widespread relevance for improving our understanding of the mechanisms which shape community structure and function.
Supervisor: Phoenix, Gareth ; Cameron, Duncan Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available