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Title: The influence of plants, ectomycorrhizal funghi and atmospheric CO₂on weathering of rocks and minerals
Author: Allinson, Kate Emma
ISNI:       0000 0004 2740 3432
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2011
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The weathering of silicate rocks and minerals plays a foundational role in soil formation, provides essential nutrient elements required by terrestrial and marine ecosystems, and regulates atmospheric CO2 concentrations over geological time through transfer of calcium from continental silicates into marine carbonate sediments. Increasing evidence from experimental and modelling studies implicate evolutionary advances in plants and their mycorrhizal fungal symbionts in enhancing weathering rates over the past 400 million years. The rise of angiosperms to ecological dominance over gymnosperms during the Cretaceous (145.5-65.5 Ma) coincided with the first appearance of ectomycorrhizal fungi, which are more aggressive weathering agents than the ancestral arbuscular mycorrhizal fungi. However, the relative importance of the plant and fungal components of biotic weathering to the long-term decline of C02 from the Cretaceous onwards has not been fully resolved. To address these issues, this thesis reports axenic microcosm experiments that are used to investigate for the first time the influences of angiosperm and gymnosperm host type and atmospheric CO2 concentration on ectomycorrhizal fungal colonisation of silicate rock grains. Using a representative gymnosperm species, Pinus sylvestris and angiosperm species, Betula pendula in symbiosis with the common generalist EM fungi Paxillus involutus, carbon fluxes from ectomycorrhizal seedlings to fungal hyphae colonising weathering arenas were quantified. 14C02 pulse labelling studies and biomass quantification techniques elucidate temporal and spatial carbon dynamics of fungal hyphae colonising grains of basalt, apatite, granite and quartz. Fungal alteration of silicate mineral surfaces was investigated by vertical scanning interferometry and the formation of new biogenic minerals studied by scanning electron microscopy. Additional experiments investigated the effects of the generalist fungus Thelephora terrestris and the suilloid group specialists of the pinaceae. EM fungal proliferation and carbon allocation is shown to respond to elevated CO2 growth conditions, and to seedling host type. Furthermore, preferential fungal colonisation of the Ca and Mg rich silicate rock basalt and evidence of accelerated Ca weathering indicates a need to reassess the current paradigm of plant weathering which overlooks the eo-evolution of roots with their mycorrhizal symbionts.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available