Low-severity fire as a mechanism of organic matter protection in global peatlands: Thermal alteration slows decomposition.
Abstract
Worldwide, regularly recurring wildfires shape many peatland ecosystems to the extent
that fire-adapted species often dominate plant communities, suggesting that wildfire
is an integral part of peatland ecology rather than an anomaly. The most destructive
blazes are smoldering fires that are usually initiated in periods of drought and can
combust entire peatland carbon stores. However, peatland wildfires more typically
occur as low-severity surface burns that arise in the dormant season when vegetation
is desiccated, and soil moisture is high. In such low-severity fires, surface layers
experience flash heating, but there is little loss of underlying peat to combustion.
This study examines the potential importance of such processes in several peatlands
that span a gradient from hemiboreal to tropical ecozones and experience a wide range
of fire return intervals. We show that low-severity fires can increase the pool of
stable soil carbon by thermally altering the chemistry of soil organic matter (SOM),
thereby reducing rates of microbial respiration. Using X-ray photoelectron spectroscopy
and Fourier transform infrared, we demonstrate that low-severity fires significantly
increase the degree of carbon condensation and aromatization of SOM functional groups,
particularly on the surface of peat aggregates. Laboratory incubations show lower
CO2 emissions from peat subjected to low-severity fire and predict lower cumulative
CO2 emissions from burned peat after 1-3 years. Also, low-severity fires reduce the
temperature sensitivity (Q10 ) of peat, indicating that these fires can inhibit microbial
access to SOM. The increased stability of thermally altered SOM may allow a greater
proportion of organic matter to survive vertical migration into saturated and anaerobic
zones of peatlands where environmental conditions physiochemically protect carbon
stores from decomposition for thousands of years. Thus, across latitudes, low-severity
fire is an overlooked factor influencing carbon cycling in peatlands, which is relevant
to global carbon budgets as climate change alters fire regimes worldwide.
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https://hdl.handle.net/10161/24515Published Version (Please cite this version)
10.1111/gcb.15102Publication Info
Flanagan, Neal E; Wang, Hongjun; Winton, Scott; & Richardson, Curtis J (2020). Low-severity fire as a mechanism of organic matter protection in global peatlands:
Thermal alteration slows decomposition. Global change biology, 26(7). pp. 3930-3946. 10.1111/gcb.15102. Retrieved from https://hdl.handle.net/10161/24515.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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Neal Flanagan
Visiting Assistant Professor
Curtis J. Richardson
Research Professor of Resource Ecology in the Division of Environmental Science and
Policy
Curtis J. Richardson is Professor of Resource Ecology and founding Director of the
Duke University Wetland Center in the Nicholas School of the Environment. Dr. Richardson
earned his degrees from the State University of New York and the University of Tennessee.
His research interests in applied ecology focus on long-term ecosystem response to
large-scale perturbations such as climate change, toxic materials, trace metals, flooding,
or nutrient additions. He has specific interests in phosphor
Hongjun Wang
Research Scientist, Senior
My research focuses on C,N,P biogeochemical cycles and the related ecological processes
in wetlands, how these key elements dynamically respond to climate change, and how
we can use the biogeochemical features to improve the ecological resilience and resistance
to climate change and human disturbance, thus mitigating environmental challenges.
I also expand my basic research in peatlands to degraded farms and put the resilient
mechanism in practice to improve sustainable food, water and agri
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