EGU23-5745, updated on 10 Jan 2024
EGU General Assembly 2023
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Increased belowground tree carbon allocation in a mature mixed forest in a dry vs. a wet year

Ido Rog1,2, Boaz Hilman3,4, Hagar Fox1, Shifra Avital1, and Tamir Klein1
Ido Rog et al.
  • 1Weizmann Institute of Science, Plant and Environmental Science, Rehovot, Israel (
  • 2Plant–Soil Interactions Group, Agroscope, Zurich 8046, Switzerland (
  • 3Department of Biogeochemical Processes, Max-Planck Institute for Biogeochemistry, Jena, 07745, Germany
  • 4The Institute of Earth Sciences, The Hebrew University of Jerusalem, Givat-Ram, Jerusalem 91904, Israel

Climate change is expected to increase the frequency and severity of droughts in Mediterranean forests. Tree survival and storage of atmospheric CO2 in these forests depend on how individual tree species allocate their carbon (C). Here, we measured a complete set of above- and belowground C pools and fluxes in five coniferous and broadleaf species co-existing in a mature evergreen forest. Our study period included a drought year, followed by an above-average wet year, and the seasonal long dry period characterizes Mediterranean climate. To quantify the exact timing and spatial distribution of belowground C allocation, we additionally applied 13CO2 pulse labelling of one of the tree species (Quercus calliprinos). We found that during the dry versus wet year, photosynthetic C uptake decreased, C use in the C sinks remained unchanged and C allocation to belowground sinks increased. Among the five major C sinks, respiration was the main flux (~64%), while smaller fluxes like exudation (~9%) and reproduction (~1%) were those which increased the most in the dry year. To cope with seasonal drought, most trees relied on starch to maintain the C supply, but between years we found no significant differences in starch and sugars in aboveground tissues. Relative to the C storage dynamics, higher water use efficiency was found in conifers, while species-specific differences between dry and wet years were found among the broadleaves. Interestingly, in the wet season, after pulse labelling, C was allocated from the labeled leaves to the roots in two main time-lags: first after 3-5 days and second after 15-20 days. Labeled C reached fine roots at a distance of 0-6 m from the labeled tree. These detailed tree-level observations expose inter-annual and interspecific differences in C allocation among fluxes and tissues, specifically in response to varying water availability.

How to cite: Rog, I., Hilman, B., Fox, H., Avital, S., and Klein, T.: Increased belowground tree carbon allocation in a mature mixed forest in a dry vs. a wet year, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5745,, 2023.