EGU23-15468
https://doi.org/10.5194/egusphere-egu23-15468
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Some forests like it cold

Albin Hammerle1, Felix Spielmann1, Katharina Scholz1, Walter Oberhuber2, and Georg Wohlfahrt1
Albin Hammerle et al.
  • 1Ecology, University of Innsbruck, Innsbruck, Austria
  • 2Botany, University of Innsbruck, Innsbruck, Austria

Forests cover roughly one third of the global land area and currently remove around one quarter of anthropogenic CO2 emissions, thus slowing down the increase in atmospheric CO2 concentrations. Forests account for approximately 90% of all terrestrial biomass, which corresponds to about 400 Gt C.

However, the ratio of carbon uptake to release is a very fragile one and is determined by many factors such as water and nutrient availability, the amount and quality of light or stand age. In addition to the factors mentioned above, temperature is one of the most important factors that determine this ratio. Both fluxes determining the net ecosystem exchange (NEE), the gross uptake of CO2 by photosynthesis (GPP) and ecosystem respiration (Reco) are sensitive to temperature. Thus, we investigated the temperature sensitivity of NEE at a newly established pine forest field site in Austria at 960 m a.s.l. Applying an understory and an ecosystem scale eddy covariance system we were able to disentangle temperature effects on understory and tree crown CO2 exchange.

We found a clear temperature optimum for CO2 uptake on ecosystem scale at around 20°C and a decrease in uptake on higher temperatures. This decrease was caused by (i) the understory turning from a slight sink for CO2 into a source of CO2 at higher temperatures, and (ii) a reduction of CO2 uptake in the tree canopy layer. Furthermore, we compared carbon flux data with continuous tree growth data from dendrometer measurements.

How to cite: Hammerle, A., Spielmann, F., Scholz, K., Oberhuber, W., and Wohlfahrt, G.: Some forests like it cold, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15468, https://doi.org/10.5194/egusphere-egu23-15468, 2023.