Key drivers of pyrogenic carbon redistribution during a simulated rainfall event
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Published:2021-02-15
Issue:3
Volume:18
Page:1105-1126
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ISSN:1726-4189
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Container-title:Biogeosciences
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language:en
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Short-container-title:Biogeosciences
Author:
Bellè Severin-LucaORCID, Berhe Asmeret AsefawORCID, Hagedorn FrankORCID, Santin Cristina, Schiedung MarcusORCID, van Meerveld IljaORCID, Abiven SamuelORCID
Abstract
Abstract. Pyrogenic carbon (PyC) is produced by the incomplete combustion of
vegetation during wildfires and is a major and persistent pool of the global
carbon (C) cycle. However, its redistribution in the landscape after fires
remains largely unknown. Therefore, we conducted rainfall simulation
experiments on 0.25 m2 plots with two distinct Swiss forest soils
(Cambisol (clay loam) and Luvisol (sandy silt)). We applied PyC produced
from wood (Picea abies) labeled under FACE conditions and C4 grass (Miscanthus sinensis) to the soil
surface to study PyC redistribution by runoff and splash and the vertical
mobility of PyC in a 10 cm unsaturated soil column based on the differences
in δ13C of soils and PyC. We assessed the effect of soil
texture, slope angle and PyC characteristics (feedstock and particle size)
on the mobility of PyC during 30 min of intense rainfall
(102 mm h−1). Our results highlight that PyC is highly mobile. Surface
runoff transported between 0.2 % and 36.0 % of the total added PyC. Erosion
by splash further redistributed 10.3 % to 25.3 % of the added PyC. Soil
type had a substantial impact on the redistribution of PyC by both runoff
and splash: on average, we recovered 10.5 % of the added PyC in runoff
and splashed material for the clay-rich Cambisol and 61.3 % of the added
PyC for the sandy silt Luvisol combined. PyC feedstock had a clear but
contrasting effect on PyC redistribution: relocation in the runoff and
splashed material was greater for wood PyC (43.4 % of total added PyC)
than grass PyC (28.4 %). However, more wood PyC (11.5 %; fraction of
organic C derived from the PyC) remained where it was initially applied
compared to grass PyC (7.4 %). The results further suggest that the
effect of PyC characteristics on its mobility can be highly variable and
depend not only on the material from which it was derived, but also on other
factors (e.g., particle size, porosity, density). In particular, the mobility
of PyC was almost twice as large for fine-grained PyC (< 63 µm) than for coarse PyC (63 µm–2 mm). Vertical mobility of PyC up
to 10 cm depth was greater in the clay-rich, well-aggregated Cambisol but
limited in the physically instable Luvisol, likely due to quick aggregate
breakdown and surface sealing. The addition of PyC to the surface of the
studied soils further induced changes in the export of native soil organic
carbon (nSOC) after the 30 min rainfall event. Our study shows that
large quantities of PyC can be redistributed by water erosion over short
timescales and that the mobility of PyC depends to a great extent on the
response of soils to rainfall. Moreover, the addition and redistribution of
PyC affects the export of nSOC and thus the C budget of fire-affected soils
and catchments.
Funder
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
Publisher
Copernicus GmbH
Subject
Earth-Surface Processes,Ecology, Evolution, Behavior and Systematics
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