EGU22-9256
https://doi.org/10.5194/egusphere-egu22-9256
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Carbon dioxide dynamics in a boreal forest ditch affected by clear-cut forestry

Alberto Zannella1, Karin Eklöf1, Hjalmar Laudon2, Eliza Maher Hasselquist2, and Marcus Wallin1
Alberto Zannella et al.
  • 1Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
  • 2Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden

Boreal water courses are large emitters of carbon dioxide (CO2) to the atmosphere. In Sweden, a high share of these water courses are man-made ditches, created to improve drainage and increase forest productivity. Previous studies from boreal regions have mainly suggested that terrestrial sources sustain the CO2 in these ditches and with variability in hydrology as the main temporal control. However, few studies have quantified ditch CO2 dynamics in harvested catchments. An altered hydrology, increased nutrient export and light availability upon forest harvest are all factors that potentially can change the main source control. Thus, there is a strong need to better understand how clear-cut forestry affects the ditch CO2 dynamics in boreal regions.

Here, high-frequency (30 min) CO2 concentration dynamics together with other hydro-chemical variables were studied in a forest ditch draining a fully harvested catchment in the Trollberget Experimental Area, northern Sweden. Data were collected during the snow-free season from May to October. Ditch CO2 concentrations displayed a clear seasonal pattern with higher CO2 during summer than in spring and autumn. Concentrations were ranging from 0.41 to 3.99 mg C L-1 (median: 1.69 mg C L-1, corresponding to partial pressures (pCO2) of 2553 μatm, IQR = 1.08 mg C L-1). Strong diel cycles in CO2 were developed during early summer, with daily amplitudes in the CO2 reaching up to 2.1 mg C L-1. These daily cycles in CO2 were likely driven by aquatic primary production consuming CO2 during daytime. In addition, individual high-flow events in response to rainfall had a major influence on the ditch CO2 dynamics with generally a diluting effect, but the strength in the CO2-discharge relationship varied among seasons and between events. It was evident from the study that growing season CO2 dynamics in forest ditches affected by clear-cut forestry are high and controlled by a combination of hydrological and biological factors. These high dynamics and the associated controls need to be considered when scaling ditch CO2 emissions across boreal landscapes affected by clear-cut forestry.

How to cite: Zannella, A., Eklöf, K., Laudon, H., Maher Hasselquist, E., and Wallin, M.: Carbon dioxide dynamics in a boreal forest ditch affected by clear-cut forestry, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9256, https://doi.org/10.5194/egusphere-egu22-9256, 2022.