EGU General Assembly 2020
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Spatial variability in terrestrial and aquatic carbon stocks and fluxes in boreal forested catchments

Nora Casson1, Adrienne Ducharme1, Geethani Amarawansha1, Geoff Gunn2, Scott Higgins2, Darshani Kumaragamage1, and Udayakantha Vitharana3
Nora Casson et al.
  • 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,, 2020

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