Spatial variability in terrestrial and aquatic carbon stocks and fluxes in boreal forested catchments
- 1University of Winnipeg, Winnipeg, Canada
- 2International Institute for Sustainable Development-Experimental Lakes Area, Winnipeg, Canada
- 3University of Peradeniya, Peradeniya, Sri Lanka
Canada’s boreal zone is a complex mosaic of forests, wetlands, streams and lakes. The pool of carbon (C) stored in each of these ecosystem components is vast, and significant to the global C balance. However, C pools and fluxes are heterogeneous in time and space, which contributes to uncertainty in predicting how a changing climate will affect the fate of C in these sensitive ecosystems. The objective of this study was to investigate factors controlling spatial variability in soil C stocks and stream C export and assess the sensitivity of these stocks and fluxes to climatic factors. We conducted a detailed examination of soil C stocks and stream dissolved organic C (DOC) export from a 320 ha boreal forested catchment located in northwestern Ontario, Canada. High-frequency stream chemistry and discharge samples were collected from three inflow streams during snowmelt and rain events from 2016-2017. An intensive soil C sampling campaign resulting in 47 surface (0 – 30 cm) samples were collected during the summer of 2019. Stream hysteresis analysis revealed marked differences in flowpaths among sub-catchments during snowmelt and rain events. In the wetland-dominated catchment, near-stream sources contributed most of the DOC export during both rainstorms and snowmelt events, but in upland-dominated catchments, the sources of DOC depended on antecedent moisture conditions. Rainstorms in these catchments following prolonged droughts resulted in DOC flushing from distal regions of the catchment. Soil C stocks were also highly spatially variable, with much of the variability being explained by local-scale factors (e.g. gravel content, soil depth, distance to the nearest ridge). Taken together, these two findings emphasize the need to consider sub-catchment scale variability when calculating C pools and fluxes in boreal catchments. This is also important when predicting how C dynamics will shift in the future as a result of shorter winters, longer droughts and more intense rainstorms.
How to cite: Casson, N., Ducharme, A., Amarawansha, G., Gunn, G., Higgins, S., Kumaragamage, D., and Vitharana, U.: Spatial variability in terrestrial and aquatic carbon stocks and fluxes in boreal forested catchments, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5558, https://doi.org/10.5194/egusphere-egu2020-5558, 2020