Mineral soils are an important intermediate storage pool of black carbon in fennoscandian boreal forests

Approximately 40% of earth's carbon (C) stored in land vegetation and soil is within the boreal region. This large C pool is subjected to substantial removals and transformations during periodic wildfire. Fire-altered C, commonly known as pyrogenic carbon (PyC), plays a significant role in fore...

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Bibliographic Details
Published in:Global Biogeochemical Cycles
Main Authors: Eckdahl, Johan A., Rodriguez, Pere Casal, Kristensen, Jeppe A., Metcalfe, Daniel B., Ljung, Karl
Format: Article in Journal/Newspaper
Language:English
Published: Umeå universitet, Institutionen för ekologi, miljö och geovetenskap 2022
Subjects:
black carbon
boreal wildfire
carbon cycle
fire severity
mineral soil
pyrogenic carbon
Soil Science
Markvetenskap
Geochemistry
Geokemi
Ecology
Ekologi
Fennoscandian
Online Access:http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-201580
https://doi.org/10.1029/2022GB007489
Description
Summary:Approximately 40% of earth's carbon (C) stored in land vegetation and soil is within the boreal region. This large C pool is subjected to substantial removals and transformations during periodic wildfire. Fire-altered C, commonly known as pyrogenic carbon (PyC), plays a significant role in forest ecosystem functioning and composes a considerable fraction of C transport to limnic and oceanic sediments. While PyC stores are beginning to be quantified globally, knowledge is lacking regarding the drivers of their production and transport across ecosystems. This study used the chemo-thermal oxidation at 375°C (CTO-375) method to isolate a particularly refractory subset of PyC compounds, here called black carbon (BC), finding an average increase of 11.6 g BC m−2 at 1 year postfire in 50 separate wildfires occurring in Sweden during 2018. These increases could not be linked to proposed drivers, however BC storage in 50 additional nearby unburnt soils related strongly to soil mass while its proportion of the larger C pool related negatively to soil C:N. Fire approximately doubled BC stocks in the mineral layer but had no significant effect on BC in the organic layer where it was likely produced. Suppressed decomposition rates and low heating during fire in mineral subsoil relative to upper layers suggests potential removals of the doubled mineral layer BC are more likely transported out of the soil system than degraded in situ. Therefore, mineral soils are suggested to be an important storage pool for BC that can buffer short-term (production in fire) and long-term (cross-ecosystem transport) BC cycling.

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