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Mr JA SUBKE, Dr K Dinsmore
No more applications being accepted
Competition Funded PhD Project (UK Students Only)
About the Project
IMPORTANT: Whilst the deadline has been set as the 20th January 2017 for all the studentships as part of a Doctoral Training Programme, serious candidates for this particular PhD should apply by 14th December 2016 (midnight). Interviews will be held in January.
TO APPLY: Please send a CV and cover letter outlining your suitability for this studentship to Jens-Arne Subke ([Email Address Removed]).
BACKGROUND
Current policy aims to increase forestry throughout Scotland, with a target of planting 10,000 hectares (~25 Million trees) per annum for over 10 years. Forests have a high potential for carbon sequestration, particularly in young rapidly growing forest stands. However to understand the full benefit of tree planting for long-term sequestration of CO2 from the atmosphere, we need to also account for changes in the underlying soil carbon (C) stock. Soils under grassland vegetation can store substantial amounts of carbon in labile and humic forms, and the impact of transitions from pasture to forestry is ambiguous in the scientific literature; both decreases in soil C stores (Guo and Gifford, 2002), and increased overall C stock have been reported, e.g. due to reallocation of C within the soil profile. Concurrent with the significant change in vegetation is an important shift in soil microbial communities. For example, whilst roots of grasses have associations with specific fungi to form arbuscular mycorrhizal (AM), temperate trees (and coniferous trees in particular) have specific associations with different groups of fungi to form ectomycorrhizal (ECM) symbioses. The fungi involved in the two contrasting mycorrhizal forms have fundamentally different growth forms and biochemical capabilities; AM commonly show a more limited spatial reach into the soil, and produce comparatively few forms of enzymes for breaking up soil organic matter, whereas ECM often support extensive fungal networks throughout soil layers below the litter layer, and are capable of a wider variety of decomposing enzymes (Read and Perez-Moreno, 2003).
AIM
The aim of this studentship is to investigate the development of soil C stocks following a transition from pasture to forestry. Specifically, the studentship will address:
1. What are long-term impacts on C stocks of afforestation on grassland?
2. Are changes in C turnover and/or pool sizes related to plant species used in afforestations?
3. Are mycorrhizal associations (ECM or AM) critical for the stabilisation and/or decomposition of soil organic matter?
METHODS
By selecting plantations on land previously used for pasture, the aim is to establish a data set of chronosequences for which soil C stock can be established. Where possible, control sites where pasture has been continuously grazed will be used to verify potential changes in C stock and other soil parameters (e.g. pH or bulk density changes).
The role of ECM fungi in decomposing soil C stocks will be addressed by transplanting soil cores between pasture and forest sites. Nylon netting of different mesh size will be used to selectively allow or block access to transplanted soils by roots and/or mycorrhiza (Subke et al., 2011). Measurement of CO2 flux from these transplanted soils will identify increased or decreased decomposition, whilst addition of common substrates (e.g. wood or plant litter) can be used to focus on specific forms of organic matter affected by root and mycorrhizal priming.
Water samples obtained from soil solution profiles as well as stream flow in plantation and control areas will be collected over a period spanning pre-plantation and up to 1 year after planting operations end. Samples will be analysed to determine content of particulate and dissolved concentrations of C (POC and DOC, respectively) as well as organic and inorganic N and P. Measurements of water surface-atmosphere CO2 flux (evasion) will complete the total C balance for the transition period.
TRAINING
1) General field work methods, including gas flux measurements and soil transplant/mycorrhizal in-growth experiments as well as aqueous carbon sampling; critical laboratory skills include elemental analysis and stable isotope methods (13C and 15N).
2) Numeracy, data analysis, ecological modelling & informatics. These skills will be gained through targeted training courses within the IAPETUS consortium and available at Stirling or Newcastle (e.g. Programming and Analysis of Environmental Data in R, GIS & Remote Sensing for Environmental Managers).
3) Land-use policy and management (e.g. stakeholder engagement at an early stage; dialogue and advice from project partners).
4) Complementary training in transferable skills. Training in core scientific skills (data management, analysis, presentations, paper writing).
TO APPLY: Please send a CV and cover letter outlining your suitability for this studentship to Jens-Arne Subke ([Email Address Removed]).
BACKGROUND
Current policy aims to increase forestry throughout Scotland, with a target of planting 10,000 hectares (~25 Million trees) per annum for over 10 years. Forests have a high potential for carbon sequestration, particularly in young rapidly growing forest stands. However to understand the full benefit of tree planting for long-term sequestration of CO2 from the atmosphere, we need to also account for changes in the underlying soil carbon (C) stock. Soils under grassland vegetation can store substantial amounts of carbon in labile and humic forms, and the impact of transitions from pasture to forestry is ambiguous in the scientific literature; both decreases in soil C stores (Guo and Gifford, 2002), and increased overall C stock have been reported, e.g. due to reallocation of C within the soil profile. Concurrent with the significant change in vegetation is an important shift in soil microbial communities. For example, whilst roots of grasses have associations with specific fungi to form arbuscular mycorrhizal (AM), temperate trees (and coniferous trees in particular) have specific associations with different groups of fungi to form ectomycorrhizal (ECM) symbioses. The fungi involved in the two contrasting mycorrhizal forms have fundamentally different growth forms and biochemical capabilities; AM commonly show a more limited spatial reach into the soil, and produce comparatively few forms of enzymes for breaking up soil organic matter, whereas ECM often support extensive fungal networks throughout soil layers below the litter layer, and are capable of a wider variety of decomposing enzymes (Read and Perez-Moreno, 2003).
AIM
The aim of this studentship is to investigate the development of soil C stocks following a transition from pasture to forestry. Specifically, the studentship will address:
1. What are long-term impacts on C stocks of afforestation on grassland?
2. Are changes in C turnover and/or pool sizes related to plant species used in afforestations?
3. Are mycorrhizal associations (ECM or AM) critical for the stabilisation and/or decomposition of soil organic matter?
METHODS
By selecting plantations on land previously used for pasture, the aim is to establish a data set of chronosequences for which soil C stock can be established. Where possible, control sites where pasture has been continuously grazed will be used to verify potential changes in C stock and other soil parameters (e.g. pH or bulk density changes).
The role of ECM fungi in decomposing soil C stocks will be addressed by transplanting soil cores between pasture and forest sites. Nylon netting of different mesh size will be used to selectively allow or block access to transplanted soils by roots and/or mycorrhiza (Subke et al., 2011). Measurement of CO2 flux from these transplanted soils will identify increased or decreased decomposition, whilst addition of common substrates (e.g. wood or plant litter) can be used to focus on specific forms of organic matter affected by root and mycorrhizal priming.
Water samples obtained from soil solution profiles as well as stream flow in plantation and control areas will be collected over a period spanning pre-plantation and up to 1 year after planting operations end. Samples will be analysed to determine content of particulate and dissolved concentrations of C (POC and DOC, respectively) as well as organic and inorganic N and P. Measurements of water surface-atmosphere CO2 flux (evasion) will complete the total C balance for the transition period.
TRAINING
1) General field work methods, including gas flux measurements and soil transplant/mycorrhizal in-growth experiments as well as aqueous carbon sampling; critical laboratory skills include elemental analysis and stable isotope methods (13C and 15N).
2) Numeracy, data analysis, ecological modelling & informatics. These skills will be gained through targeted training courses within the IAPETUS consortium and available at Stirling or Newcastle (e.g. Programming and Analysis of Environmental Data in R, GIS & Remote Sensing for Environmental Managers).
3) Land-use policy and management (e.g. stakeholder engagement at an early stage; dialogue and advice from project partners).
4) Complementary training in transferable skills. Training in core scientific skills (data management, analysis, presentations, paper writing).
Funding Notes
This PhD is part of IAPETUS (http://www.iapetus.ac.uk/), a Doctoral Training Programme. Supervision will be provided by Dr Jens-Arne Subke (University of Stirling), and Dr Kerry Dinsmore (CEH Edinburgh).
This is a 3.5 year PhD studentship with a stipend set at the RCUK national rate (forecast to be £14,296) with an anticipated start date of October 2017.
To be eligible for a full award a student must be a UK citizen or have been resident in the UK for a period of 3 years or more. http://www.rcuk.ac.uk/documents/documents/termsconditionstraininggrants-pdf/
This is a 3.5 year PhD studentship with a stipend set at the RCUK national rate (forecast to be £14,296) with an anticipated start date of October 2017.
To be eligible for a full award a student must be a UK citizen or have been resident in the UK for a period of 3 years or more. http://www.rcuk.ac.uk/documents/documents/termsconditionstraininggrants-pdf/
References
Guo, L., Gifford, R., 2002. Soil carbon stocks and land use change: A meta analysis. Global Change Biology 8, 345-360.
Read, D.J., Perez-Moreno, J., 2003. Mycorrhizas and nutrient cycling in ecosystems - a journey towards relevance? New Phytologist 157, 475-492.
Subke, J.A., Voke, N.R., Leronni, V., Garnett, M.H., Ineson, P., 2011. Dynamics and pathways of autotrophic and heterotrophic soil CO2 efflux revealed by forest girdling. Journal of Ecology 99, 186-193.
Talbot, J.M., Allison, S.D., Treseder, K.K., 2008. Decomposers in disguise: Mycorrhizal fungi as regulators of soil C dynamics in ecosystems under global change. Functional Ecology 22, 955-963.
Read, D.J., Perez-Moreno, J., 2003. Mycorrhizas and nutrient cycling in ecosystems - a journey towards relevance? New Phytologist 157, 475-492.
Subke, J.A., Voke, N.R., Leronni, V., Garnett, M.H., Ineson, P., 2011. Dynamics and pathways of autotrophic and heterotrophic soil CO2 efflux revealed by forest girdling. Journal of Ecology 99, 186-193.
Talbot, J.M., Allison, S.D., Treseder, K.K., 2008. Decomposers in disguise: Mycorrhizal fungi as regulators of soil C dynamics in ecosystems under global change. Functional Ecology 22, 955-963.