NSFDEB-NERC:Mycorrhizal drivers of SOM formation and decomposition

Lead Research Organisation: University of Stirling
Department Name: Biological and Environmental Sciences


Soils in natural temperate ecosystems store substantial amounts of carbon in the form of soil organic matter. This represents a vital service by these ecosystems (including forest, grasslands as well as wetlands), as these organic matter reservoirs have been built up from decaying vegetation that previously fixed carbon in its biomass from atmospheric CO2. There is significant uncertainty regarding the persistence of this reservoir of carbon in soils, both from climatic influences and changes in land use.

The influence of temperature on the formation of plant biomass as well as decay processes are well researched, but have so far been largely considered separately. More recently, it has emerged that fundamental differences in the way in which vegetation interacts with microbial organisms in the soil have significant impact on the storage of carbon in soil organic matter. The symbiotic relationship of plants with particular forms of fungi (mycorrhizas) is of particular interest. The role of these fungi in the supply of nutrients to plants is well established, but recent findings highlight important influences of these organisms also on the formation and decomposition of organic matter. Changes in vegetation form can drastically influence the type of fungal (i.e. mycorrhizal) diversity in the soil, with direct implications for organic matter formation and decay. However, the interaction between vegetation form, fungal association and soil organic matter storage has not been investigated systematically.

This research addresses the way in which changes in vegetation that also alter the type of mycorrhizal fungal association results in changes in organic matter storage. Specifically, we will investigate a switch from grasslands to coniferous forests. This kind of vegetation change is relatively common in temperate regions due to an encroachment of trees near treelines, following a warming climate, and managed land use changes where upland pasture may be planted with commercial forestry or for 'rewilding' efforts. Our methodology combines experimental decomposition studies with ecosystem model development to enable a new generation of predictive models (based on existing modelling tools) able to incorporate plant-microbial interactions. Land managers and policy makers alike require a full understanding of the consequences of this kind of vegetation change on soil carbon storage, as apparent benefits in carbon uptake by vegetation may be annulled by corresponding losses in storage within the soil.

Planned Impact

This is a 'Discovery Science' proposal, addressing a fundamental aspect of the terrestrial C cycle. As such, it has important implications in global change science, for ecosystem management, and for broader society. The focus of experiments and modelling efforts are on the understanding of feedbacks between vegetation and the soil biota with regards to the formation and decomposition of soil organic matter. We hypothesise significant shifts in the processing and ultimately longevity of soil organic matter in soils in response to vegetation change, which has profound implications to carbon storage and climate feedbacks for natural and managed ecosystems.

Results of this research are of immediate interest to the global change biology and climate sciences research communities, as well as to national and international policy makers. The aim of current modelling efforts in the atmospheric and ecosystem communities is to understand future CO2 burdens based on on-going and projected environmental conditions resulting from climatic change and human land use. The novel soil module developed here to reflect vegetation change will be integrated into ecosystem models currently used to assess carbon storage and release in ecosystems.

The result will further benefit statutory agencies and land managers concerned with carbon sequestration and storage in relation to land use. The Forestry Commission (and more specifically its research branch Forest Research) as well as commercial forestry operators and nature charities involved in tree plantation under current 'rewilding' schemes require more knowledge of the impact of vegetation change. National and regional land use policies will have to reflect all ecosystem services associated with land management decisions, and the proposed research would fill a gap in our knowledge regarding vegetation feedbacks on long term carbon storage.

Ultimately, these insights are for the benefit of society in general. Whether land cover change occurs as a consequence of global changes, or as a result of deliberate management, the consequences for belowground carbon storage have to be understood. Communities living and working in areas where changes occur (often areas of low agricultural productivity, such as UK uplands) are aware of the on-going and changing land-use demands, potential conflicts, and the challenges of earning a viable living. It is important that society has a robust science base upon which to develop rational policies for upland land-use, and that the ecosystem services provided in these areas can be sustainably managed. Furthermore, through their effects on biodiversity and landscape quality, 're-wilding' and forest regeneration will have significant implications for quality of life, health and aesthetic value.
Description Our data show a clear reduction in mineral soil carbon storage following afforestation, challenging assumptions regarding carbon sequestration potential of forests. For forests up to 60 years, and planted on former pasture soils, this means that the total amount of c sequestered from the atmosphere is about half that of what is stored in tree biomass only.
Exploitation Route Once published, we intend to expand on the novel results showing reduction in soil C stocks associated with greater tree biomass to investigate the role of specific vegetation, and specifically the role of associated mycorrhizal associations.
Sectors Environment,Government, Democracy and Justice

Description What drives the quality and decay of soil detritivore faeces: the ingested litter quality, or the animal identity?
Amount £4,431 (GBP)
Organisation British Ecological Society 
Sector Charity/Non Profit
Country United Kingdom
Start 05/2018 
End 05/2019
Title Radiocarbon dating of soil organic matter average ages of soil organic matter (bulk and fractions) from the 0-5cm layer, collected in contrasting vegetation types in the Scottish lowlands 
Description Radiocarbon dating of soil organic matter: this dataset contains average ages of soil organic matter (bulk and fractions) from the 0-5cm layer, collected in contrasting vegetation types in the Scottish lowlands (Scots pine forests vs. grasslands), estimated using radiocarbon dating 
Type Of Material Database/Collection of data 
Year Produced 2019 
Provided To Others? No  
Impact Validation dataset to be used for evaluation of turnover times modelled using MEMS. 
Description Dr Carsten Mueller 
Organisation University of Copenhagen
Country Denmark 
Sector Academic/University 
PI Contribution Research visit by PDRA to Dr Mueller's lab (whilst employed at TU Muenchen),and continued collaboration of lab members.
Collaborator Contribution Dr Carsten Mueller is research group leader in the Geography Department and collaborates on this grant in his personal expertise in 13C-NMR and nanoSIMS to identify soil organic matter properties
Impact NMR and nanoSIMS evaluation planned for 2021, with publications forthcoming either late 2021 or in 2022.
Start Year 2020
Description Forest Research 
Organisation Forest Research
Country United Kingdom 
Sector Public 
PI Contribution Scientific leadership of belowground C dynamics in forest sites.
Collaborator Contribution Guidance in selection of suitable sites; Soil profile sampling.
Impact None to date
Start Year 2017
Description Francesca Cotrufo and group 
Organisation Colorado State University
Country United States 
Sector Academic/University 
PI Contribution Field work on grant; expertise in mycorrhizal manipulations and CO2 flux measurements; incubation of isotopicallylabelled materials
Collaborator Contribution Training of PDRA in soil fractionation techniques; growing of isotopically labelled biomass; modelling of C dynamics at our filed sites
Impact None to date
Start Year 2017
Description Technische Universitaet Muenchen 
Organisation Technical University of Munich
Country Germany 
Sector Academic/University 
PI Contribution Scientific leadership on current grant; collaboration in Special Issue of Frontiers in Plant Science (initiated by partner)
Collaborator Contribution Analyses of soil samples (nanoSIMS); invitation to join editorial group of Special Issue of Frontiers in Plant Science
Impact Special Issue of Frontiers in Plant Science (in progress)
Start Year 2017
Description From plant input to soil organic matter: the role of mycorrhizal fungi 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Thematic session at the Annual Meeting of the British Ecological Society in December 2019 (Belfast). The session was proposed and co-chaired by Dr. Francois-Xavier Joly, and brought together experts on soil organic matter formation and decomposition from across Europe and the US.
Year(s) Of Engagement Activity 2019
URL https://www.britishecologicalsociety.org/events/annual-meeting-2019/call-thematic-sessions/
Description Pint of Science 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Public/other audiences
Results and Impact Pint of Science presentation on: "Where has all the carbon gone?"
Year(s) Of Engagement Activity 2019
Description UK soil organic carbon data and modelling; 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact the aim of the workshop was to share future thinking with respect to soil protection policies across Scotland, Wales, England and Northern Ireland. It explored how our current research activities can support these initiatives going forward to ensure national policies are met whilst maintaining a UK-wide perspective and connection.
Year(s) Of Engagement Activity 2019