Preprints
https://doi.org/10.5194/acp-2021-641
https://doi.org/10.5194/acp-2021-641

  19 Oct 2021

19 Oct 2021

Review status: this preprint is currently under review for the journal ACP.

Biogeochemical and biophysical responses to episodes of wildfire smoke from natural ecosystems in southwestern British Columbia, Canada

Sung-Ching Lee1, Sara H. Knox1, Ian McKendry1, and T. Andrew Black2 Sung-Ching Lee et al.
  • 1Department of Geography, University of British Columbia, Vancouver, Canada
  • 2Faculty of Land and Food Systems, University of British Columbia, Vancouver, Canada

Abstract. Area burned, number of fires, seasonal fire severity, and fire season length are all expected to increase in Canada, with largely unquantified ecosystem feedbacks. However, there are few observational studies measuring the ecosystem‐scale biogeochemical and biophysical properties during smoke episodes, and hence accessing productivity effects of changes in incident diffuse photosynthetically active radiation (PAR). In this study, we leverage two long-term eddy covariance measurement sites in forest and wetland to study four smoke episodes, which happened at different times and differed in length, over four different years. We found that the highest decrease of shortwave irradiance due to smoke was about 50 % in July and August but increased to about 90 % when the smoke arrived in September. When the smoke arrived in the later stage of summer, impacts on H and LE were also greatest. Smoke generally increased the diffuse fraction from ~0.30 to ~0.50 and turned both sites into stronger carbon-dioxide (CO2) sinks with increased productivity of ~18 % and ~7 % at the forest and wetland sites, respectively. However, when the diffuse fraction exceeded 0.80 as a result of dense smoke, both ecosystems became CO2 sources as total PAR dropped to low values. The results suggest that this kind of natural experiment is important for validating future predictions of smoke‐productivity feedbacks.

Sung-Ching Lee et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-641', Anonymous Referee #2, 11 Nov 2021
  • RC2: 'Comment on acp-2021-641', Anonymous Referee #1, 13 Nov 2021

Sung-Ching Lee et al.

Sung-Ching Lee et al.

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Short summary
Wildfire smoke alters land-atmosphere exchange. Here, measurements in a forest and a wetland during four smoke episodes over four summers showed that impacts on radiation and heat budget were the greatest when smoke arrived in late summer. Both sites sequestered more CO2 under smoky days partly due to diffuse light, but emitted CO2 when smoke was dense. This kind of field study is important for validating predictions of smoke‐productivity feedbacks and has climate change implications.
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