Science challenge

We aim to better understand the biotic and abiotic controls on the dynamics of soil organic carbon, to determine where UK soil carbon stocks are most at risk of loss, and to identify opportunities to increase soil carbon storage through land management policies and practices.

Soils underpin many important aspects of a functioning society including agriculture, food security, climate change mitigation, flood risk management and urban development. Soil organic carbon (SOC) content is a critical soil property contributing to these functions.

The dynamics of SOC are complex and highly variable depending on geology, climate, vegetation and land-use. Changes in SOC can be gradual in response to chronic pressures (such as climate change) or rapid when acute disturbances occur (for example, land use change and/or pollutant contamination).

There are critical uncertainties in our understanding of SOC dynamics which limit our ability to forecast the likely rate and extent of soil carbon change in response to the complex interacting set of local and global drivers.

“Healthy soils (both urban and rural) are important for food production and human wellbeing. Soil health cannot be measured directly, so indicators (physical, chemical, and biological properties, processes, or characteristics) are generally used. These measurable properties of soil or plants provide clues about how well the soil can function.”

House of Commons Environmental Audit Committee Report on Soil Health 2016-17

Project summary

Recent reviews and initiatives such as the NERC Soil Security Programme highlight a paradigm shift in our understanding of critical controls on SOC from strictly chemical to biological and structural processes. The SOC-D project tested the evidence base for these critical controls in all key UK land use-soil combinations. The project also identified potential causal links between soil biota, soil structure and soil function using UKCEH’s 40 year national soil monitoring programme, and long term experimental and monitoring sites maintained by UKCEH and our partners. SOC-D exploited a range of technologies to capture new knowledge and build a flexible, modular, process-based model of SOC dynamics which can also be embedded within other community soils models.

Science Questions

• What is the sensitivity of SOC to local or global changes in climate and land management?
• What critical feedbacks link SOC with soil structure, chemistry and functional biota?
• What soil metrics and modelling approaches best reflect the new understanding of SOC dynamics?
• What areas in the UK are most at risk of losing SOC, and where can SOC be protected or increased?

Objectives

We aim to better understand the physical, chemical and biological factors affecting soil organic carbon (SOC), to determine where carbon stocks are most at risk in UK soils, and to identify ways to increase soil carbon storage through improved land management policy and practice.

Overarching question

How do biotic and abiotic controls and feedbacks affect SOC stability?

Innovative solution

We integrate novel data streams and traditional soil metrics to produce new process understanding, sharing this knowledge through an open-access SOC-D Model and Data Framework.

Field approach: co-located soil and vegetation studies

The SOC-D field programme is a national scale effort focused on poorly understood processes affecting SOC (such as effective net primary production to soils, below-ground carbon allocation, soil community impacts). The field programme is an open community effort exploiting the unique resources of UKCEH and external partners and includes:

• Sites covering all major UK soil-land use combinations:
  • Long-term national soil survey locations with known land use change and soil properties
  • Network of land-use transition sites and long-term experiments
• Measurements of soil samples to 1m depth:
  • Covering a range of soil biological, physical and chemical measurements
  • Linked vegetation characteristics above and below ground (for example, net primary production and rooting traits)
• Next generation of experiments and tools:
  • Isotopes, drones and earth observation.

Modelling approach - 'living dynamic soil'

Central to the SOC-D modelling programme is the creation of a modelling framework that can be used to evaluate SOC models against large-scale monitoring networks and research platforms. The modelling programme uses modular, open-source development, building on existing resources of UKCEH and external partners to benefit the wider community. Modelling activities focus on two primary dynamics of SOC:

• SOC formation and distribution:
  • Spatial patterns of plant primary production in the UK
  • Role of plant roots relative to leaf litter in contributing to SOC formation
  • Relative importance of mineral-associated vs particulate processes
• SOC persistence:
  • Dynamic zones of influence from upper plant zone to lower mineral-matrix zone
  • Nationally relevant soil microbial taxa and genes affecting SOC formation and persistence
  • Interactions of soil microbes, animals and mycorrhiza on SOC turnover rates, distribution and feedback on water hydraulic properties.

Resources

Project outputs

• A national network of co-located soil and vegetation plots combining biodiversity, physical, chemical and carbon process measurements
• A national-scale modelling and data framework for SOC dynamics with national datasets identifying risks and opportunities for UK soils
• Community access to datasets and models through the UK-SCAPE Data Science Framework
• New policy and decision support tools for sustainably managing UK soils.

Interactions

Science and policy impacts

• Step change in our understanding of soil carbon dynamics
• More robust representation of soil processes in Integrated Modelling Frameworks
• Improved decision support for informing strategies to meet targets such as:
  1. Defra 25 year plan
  2. UN Framework Convention on Climate Change
  3. UN Sustainable Development Goals (e.g., 15.3)
  4. Natural Capital accounting.

• Support for development of national policies to protect soil health (see the report from the SOC-D sponsored National Soil Health Policy Workshop).

Opportunities for the wider community

• Potential for shared, co-located soil-vegetation studies to improve understanding in areas with poor consensus (e.g. below-ground carbon allocation, soil community impacts)
• Open access to SOC-D data and models through UKSCAPE Data Science Framework
• Access to UKCEH Soil Bank, UKCEH’s National ‘Living’ Soil Archive of frozen and air-dried soil samples
• SOC-D research, in collaboration with our community partners, has led to the development of new research projects to investigate large-scale removal of greenhouse gases (funded by the Government’s Strategic Priorities Fund; SPF)
• SOC-D community engagement has contributed to the development of UKSoils (uksoils.org), a new online community hub to inspire action to protect our soils.