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Can Increased Plant Diversity Restore Soil-Associated Ecosystem Services in Agroecosystems Experiencing Variable Rainfall Patterns?

Postgraduate Training

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Dr T George , Dr A Karley , Prof I Dodd No more applications being accepted Competition Funded PhD Project (UK Students Only)

About the Project

Rationale. Agriculture accounts for 72% of UK land area (Defra agriculture statistics, 2019). While agricultural intensification has successfully delivered food and fuel to the UK economy, it has simplified agricultural landscapes thereby reducing biodiversity, depleting natural resources, and threatening ecosystem services (IPBES Global Assessment Report, 2019). This loss of diversity might also reduce resilience to abiotic stress, creating uncertainty about effects of the changing climate on agricultural production and environmental degradation. Increasing agricultural plant diversity could address all these issues and restore agroecosystem functions. Species-rich systems often show increased productivity, improved resource use efficiency and other indirect benefits such as pest and disease suppression1, and greater resilience to abiotic stress (e.g. aridity2). While much research has focused on the direct benefits of increased plant diversity for crop productivity, quantifying the indirect benefits on agroecosystem natural resources has attracted less attention. In particular, the multiple ecosystem services regulated by crop root systems (e.g. limiting soil erosion, building soil carbon stores, reducing pollution from nutrient leaching) have been relatively ignored.
Aims. This project aims to address the significant knowledge gap in potential benefits of increased plant diversity for boosting soil (carbon, nutrient) stocks and soil-associated ecosystem services in agroecosystems. By examining three typologies of crop vegetation systems, ranging from diverse vegetation in undisturbed soil (species-rich pasture) to monocrops in highly disturbed soils (e.g. arable), the studentship will quantify how plant diversity affects ecosystem service delivery and characterise the underpinning mechanisms at different experimental scales. Emphasis will be placed on understanding the regulation of these processes under climate (especially rainfall) variability. By providing scientific evidence for the effects of increased plant diversity on agroecosystem function, the project findings will inform land managers of cropping practices to conserve soil stocks and function and aid in delivering environmental policy targets for agriculture.
Objectives. Our hypothesis is that increased plant diversity optimizes soil function and minimizes system degradation by allowing complementary use of the soil volume and soil resources in time and space. Research across different experimental scales will quantify the effects of increased plant diversity on soil stocks and soil-associated ecosystem services in agroecosystems, to address the following objectives and outline plan:
Obj.1 Survey the literature to identify species combinations suitable for studying the research hypothesis (Y1), comprising vegetation types of different levels of diversity relevant to UK agriculture;
Obj. 2 Determine below-ground mechanisms leading to improved nutrient retention and reduced water flow and erodibility in vegetation of increasing diversity under different precipitation scenarios (Y1-2);
Obj. 3 Quantify soil stocks and ecosystem services under different levels of plant diversity at field scale (Y2-3);
Obj. 4 Knowledge transfer to land managers and other stakeholders (Y2.5-3.5).
Methods and approach. Different research methods will be applied at scales ranging from mesocosms to large-scale field platforms. The literature analysis in Y1 (Obj. 1, month 1-3) will inform experiment design (Obj. 2), including establishing an experimental field platform (Obj. 3). For the experimental work (Obj. 2 and 3), gradients of plant diversity and soil water availability will be imposed, with appropriate control treatments, across three typologies of crop vegetation: i) monocropping (e.g. potato); ii) monocrops with companion plant species (e.g. under-sown legumes); iii) species-rich vegetation (e.g. grass-legume mixtures in established pasture). In Y1 (month 4-12), mesocosm experiments (Obj. 2) will be conducted to quantify soil functions (water relations, soil nutrient/carbon retention) and plant resource capture (water and nutrient uptake) in relation to root placement and architecture under different levels of plant diversity and altered patterns of water availability (imposed by a rainfall simulator). Methods will include stable isotope labelling, nutrient analysis (e.g. by ICP-ES, colorimetric or combustion methods) and environmental monitoring (soil pH, moisture, temperature, humidity). Data analysis will require parametric tests and multivariate methods to explore associations between the measured variables. In Y2-3, a field experiment (Obj. 3) established at Hutton (in Y1) with different levels of plant diversity will be used to quantify processes of erosion, water flow, carbon storage and nutrient leaching, as well as plant productivity and nutrient capture, to confirm findings of mesocosm studies and to measure processes occurring at larger scales. In the later stages of the project, findings about the effects of increasing plant diversity on soil preservation and function will be communicated to farmers, scientists and other stakeholders at appropriate events.

Funding Notes

The studentship is funded under the James Hutton Institute/University Joint PhD programme, in this case with the University of Lancaster for a period of 3.5 years. Applicants should have a first-class honours degree in a relevant subject or a 2.1 honours degree plus Masters (or equivalent).Shortlisted candidates will be interviewed in Jan/Feb 2021. A more detailed plan of the studentship is available to candidates upon application. Funding is available for UK applications only. The James Hutton Institute is an equal opportunity employer. We celebrate diversity and are committed to creating an inclusive environment for all employees and students

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