Boreal forest soil carbon fluxes one year after a wildfire: Effects of burn severity and management

Julia Kelly, Theresa S. Ibáñez, Cristina Santín, Stefan H. Doerr, Marie Charlotte Nilsson, Thomas Holst, Anders Lindroth, Natascha Kljun

Research output: Contribution to journalArticlepeer-review

Abstract

The extreme 2018 hot drought that affected central and northern Europe led to the worst wildfire season in Sweden in over a century. The Ljusdal fire complex, the largest area burnt that year (8995 ha), offered a rare opportunity to quantify the combined impacts of wildfire and post-fire management on Scandinavian boreal forests. We present chamber measurements of soil CO2 and CH4 fluxes, soil microclimate and nutrient content from five Pinus sylvestris sites for the first growing season after the fire. We analysed the effects of three factors on forest soils: burn severity, salvage-logging and stand age. None of these caused significant differences in soil CH4 uptake. Soil respiration, however, declined significantly after a high-severity fire (complete tree mortality) but not after a low-severity fire (no tree mortality), despite substantial losses of the organic layer. Tree root respiration is thus key in determining post-fire soil CO2 emissions and may benefit, along with heterotrophic respiration, from the nutrient pulse after a low-severity fire. Salvage-logging after a high-severity fire had no significant effects on soil carbon fluxes, microclimate or nutrient content compared with leaving the dead trees standing, although differences are expected to emerge in the long term. In contrast, the impact of stand age was substantial: a young burnt stand experienced more extreme microclimate, lower soil nutrient supply and significantly lower soil respiration than a mature burnt stand, due to a thinner organic layer and the decade-long effects of a previous clear-cut and soil scarification. Disturbance history and burn severity are, therefore, important factors for predicting changes in the boreal forest carbon sink after wildfires. The presented short-term effects and ongoing monitoring will provide essential information for sustainable management strategies in response to the increasing risk of wildfire.

Original languageEnglish
Pages (from-to)4181-4195
JournalGlobal Change Biology
Volume27
Issue number17
Early online date2021 May 24
DOIs
Publication statusPublished - 2021

Bibliographical note

Funding Information:
This project has been funded by Swedish Research Council Formas grants 2018‐02700, 2019‐00836, the strategic research program of the Crafoord Foundation grant 20190763, and the Swedish Strategic Research Area BECC (Biodiversity and Ecosystem Services in a Changing Climate). C.S. also received funding from the Spanish ‘Ramon y Cajal’ programme, Ref. N. RYC2018‐025797‐I. Jukka Kuivaniemi has been integral to the success of the project, and we thank him for facilitating access to the sites and tree‐ring dating. We also thank him and Mårten Sörell for detailed information on the sites and forest management practices. We are grateful to Olle Olmårs for providing access to the HY and SHM sites, to Ellinor Delin for conducting a vegetation survey, to Niklas Båmstedt and Malin Blomberg for their assistance with the fieldwork and to Louise Andresen, for her insightful comments on the soil chemistry analysis.

Publisher Copyright:
© 2021 The Authors. Global Change Biology published by John Wiley & Sons Ltd.

Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.

Subject classification (UKÄ)

  • Soil Science

Keywords

  • 2018 drought
  • boreal forest
  • carbon fluxes
  • climate change
  • compound disturbance
  • forest fire
  • forest floor
  • harvesting
  • salvage-logging

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