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Contemporary carbon balance and late Holocene carbon accumulation in a northern peatland
Author(s) -
ROULET NIGEL T.,
LAFLEUR PETER M.,
RICHARD PIERRE J. H.,
MOORE TIM R.,
HUMPHREYS ELYN R.,
BUBIER JILL
Publication year - 2007
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1111/j.1365-2486.2006.01292.x
Subject(s) - ombrotrophic , peat , bog , environmental science , carbon cycle , dissolved organic carbon , holocene , ecosystem , carbon fibers , atmosphere (unit) , atmospheric sciences , hydrology (agriculture) , physical geography , climatology , chemistry , environmental chemistry , ecology , geography , geology , oceanography , biology , materials science , geotechnical engineering , composite number , meteorology , composite material
Northern peatlands contain up to 25% of the world's soil carbon (C) and have an estimated annual exchange of CO 2 ‐C with the atmosphere of 0.1–0.5 Pg yr −1 and of CH 4 ‐C of 10–25 Tg yr −1 . Despite this overall importance to the global C cycle, there have been few, if any, complete multiyear annual C balances for these ecosystems. We report a 6‐year balance computed from continuous net ecosystem CO 2 exchange (NEE), regular instantaneous measurements of methane (CH 4 ) emissions, and export of dissolved organic C (DOC) from a northern ombrotrophic bog. From these observations, we have constructed complete seasonal and annual C balances, examined their seasonal and interannual variability, and compared the mean 6‐year contemporary C exchange with the apparent C accumulation for the last 3000 years obtained from C density and age‐depth profiles from two peat cores. The 6‐year mean NEE‐C and CH 4 ‐C exchange, and net DOC loss are −40.2±40.5 (±1 SD), 3.7±0.5, and 14.9±3.1 g m −2 yr −1 , giving a 6‐year mean balance of −21.5±39.0 g m −2 yr −1 (where positive exchange is a loss of C from the ecosystem). NEE had the largest magnitude and variability of the components of the C balance, but DOC and CH 4 had similar proportional variabilities and their inclusion is essential to resolve the C balance. There are large interseasonal and interannual ranges to the exchanges due to variations in climatic conditions. We estimate from the largest and smallest seasonal exchanges, quasi‐maximum limits of the annual C balance between 50 and −105 g m −2 yr −1 . The net C accumulation rate obtained from the two peatland cores for the interval 400–3000 bp (samples from the anoxic layer only) were 21.9±2.8 and 14.0±37.6 g m −2 yr −1 , which are not significantly different from the 6‐year mean contemporary exchange.