- 1School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, UK
- 2Birmingham Institute of Forest Research, University of Birmingham, Birmingham, UK
- 3Institute of Ecology and Environmental Sciences (IEES), CNRS, INRAE, Sorbonne Université, Paris, France
- 4Priestley Centre for Climate Futures, University of Leeds, Leeds, UK
- 5Lancaster Environment Centre, Lancaster University, Lancaster, UK
Tree roots adapt their morphological, physiological and biochemical functional traits to optimise nutrient acquisition, notably in response to global changes. Therefore, it is hypothesized that, to increase nutrient acquisition under elevated CO2 (eCO2) to sustain productivity, trees will allocate more carbon assimilates into their root systems. As fine roots are thought to represent ~1/3 of global NPP, understanding how much of the additional carbon (C) introduced into the forest ecosystem by increased photosynthesis is allocated belowground, will improve the accuracy of coupled biosphere-atmosphere models and our understanding of future global C budgets.
We assess the effect of eCO2 on the biomass, morphology, depth distribution and turnover of fine roots of 180-year-old English Oak trees in years 4-7 of an ongoing study (2017-2031) at the Birmingham Institute of Forest Research free air carbon dioxide enrichment (BIFoR FACE) experiment. BIFoR FACE is currently the only experiment in a mature temperate forest simulating the CO2 concentrations predicted to be the 2050 planetary norm (+150ppm above ambient). For ambient and eCO2 treatments, 1-metre soil cores were used to assess fine root standing stock, morphology (length, diameter and specific root length (SRL)) and depth distribution. A minirhizotron camera was used to assess fine root production, mortality and turnover across 2 years.
There was >40% more fine root biomass under eCO2 in all depth profiles down to 50cm, driven by an increase in fine root length. This displays how more carbon assimilates were allocated to the fine root systems of this mature, temperate forest under eCO2. Below 50cm the roots were longer and thinner under eCO2, showing how an increase in the available surface area of the root system for nutrient uptake is achieved through a shift in morphology alongside an increase in standing stock. Contrary to our expectation, the distribution of fine root biomass did not shift to greater depths under eCO2. Long-term minirhizotron data shows strong seasonal cycles in fine root production and mortality, modulated by eCO2.
How to cite: Handy, G., Arnaud, M., Esquivel-Muelbert, A., Carter, I., Kourmouli, A., Mayoral, C., and Mackenzie, A. R.: Changed Root Dynamics in a Mature Temperate Forest Under Elevated CO2, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17161, https://doi.org/10.5194/egusphere-egu25-17161, 2025.
