Abstract
AbstractNorthern peatlands are a large source of atmospheric methane (CH4) and both a source and a sink of atmospheric carbon dioxide (CO2). The rate and temporal variability in gas exchanges with peat soils is directly related to the spatial distribution of these free‐phase gases within the peat column. In this paper, we present results from surface and borehole ground‐penetrating radar surveys – constrained with direct soil and gas sampling – that compare the spatial distribution of gas accumulations in two raised bogs: one in Wales (UK), the other in Maine (USA). Although the two peatlands have similar average thickness, physical properties of the peat matrix differ, particularly in terms of peat type and degree of humification. We hypothesize that these variations in physical properties are responsible for the differences in gas distribution between the two peatlands characterized by (1) gas content up to 10.8% associated with woody peat and presence of wood layers in Caribou Bog (Maine) and (2) a more homogenous distribution with gas content up to 5.7% at the surface (i.e. <0.5 m deep) in Cors Fochno (Wales). Our results highlight the variability in biogenic gas accumulation and distribution across peatlands and suggest that the nature of the peat matrix has a key role in defining how biogenic gas accumulates within and is released to the atmosphere from peat soils. © 2015 The Authors. Hydrological Processes published by John Wiley & Sons Ltd.
Highlights
Peatlands are a critical component of the global carbon (C) cycle accounting for 30% of all global soil C and containing the equivalent of 75% of the atmospheric C store (Parish et al, 2008)
Two major differences exist between the sites: (1) average gas contents range between 2.5% and 5.7% within Cors Fochno and between 5.5% and 10.8% in Caribou Bog, with the average gas content in Caribou Bog (7.8%) being more than twice that in Cors Fochno (3.8%); and (2) maximum variability of all gas contents along the peat column is only 3.1% in Cors Fochno relative to 5.3% in Caribou Bog
This paper highlights differences in vertical biogenic gas distribution in two raised bogs characterized by very similar thickness of the peat column but different peat types
Summary
Peatlands are a critical component of the global carbon (C) cycle accounting for 30% of all global soil C and containing the equivalent of 75% of the atmospheric C store (Parish et al, 2008). Release of biogenic gases in peatlands occurs by diffusion, transport through vascular plants or ebullition (either episodic or steady). The role of ebullition as a pathway for C loss from peat soils has been the focus of several recent studies that consider ebullition an underestimated source of atmospheric C (Rosenberry et al, 2006). Uncertainty exists regarding whether ebullition events are primarily sustained by deep or shallow biogenic gas sources within the peat column (Coulthard et al, 2009)
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