Understanding the input of carbon from tree roots to soils in drier forests (RadiCs)

• Applicant: Dr. Emily Solly
• Subject Area: Soil Sciences ; Forestry
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 566603670

Forests cover nearly a third of the Earth’s land surface, provide many services to society and store a significant amount of carbon. With ongoing climate change, forests are facing an intensification of environmental disturbances related to warming and changing precipitation patterns such as more frequent and intense periods of drought. While important advances have been made to improve our understanding of forest productivity and tree physiological responses to drier environmental conditions, effects on belowground processes remain elusive, despite their importance for shaping forest functioning and the cycling of carbon. In particular, there are still substantial uncertainties about how drier conditions affect i) root lifespans, distributions and tissue quality across soil profiles, ii) the transit times of carbon from trees to soils, and iii) the formation of soil organic carbon through a potentially altered belowground biological activity, at different soil depths. To fill these research gaps, the main objective of the proposed project is to unravel how drier conditions affect the input of root carbon to forest soils. To reach this objective, regional field-based studies in mature forest stands dominated by European beech along a precipitation gradient will be conducted and combined with a mechanistic study with European beech-forest soil mesocosms under controlled conditions. Fine root lifespans, distributions and tissue quality will be determined across soil profiles in hydrologically-distinct forests in Germany using root anatomy techniques to record the chronological ages of fine roots, assessments of root growth and root biomass, and analytical measurements to quantify the chemical composition of fine roots. At the same forest stands, radiocarbon measurements of soluble and structural carbon in roots collected from individual trees will provide fundamental insights on how long carbon taken up via photosynthesis resides in trees before it is transferred to the soil through fine root systems. In the mesocosm study, tree structural and physiological responses will be measured in parallel to changes in fungal mycelia production, root associated and soil fungal communities, and soil physicochemical properties, to quantify the influence of an altered biological activity in response to drier environmental conditions on the formation of soil organic carbon at different soil depths. The proposed research will lead to key insights on how belowground processes in forests respond to a drier environment and will thus ultimately contribute to a better understanding of the cycling of carbon at the tree-soil interface under changing precipitation patterns.

• DFG Programme: Research Grants