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A large proportion of N orth A merican net ecosystem production is offset by emissions from harvested products, river/stream evasion, and biomass burning
Author(s) -
Turner David P.,
Jacobson Andrew R.,
Ritts William D.,
Wang Weile L.,
Nemani Ramakrishna
Publication year - 2013
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/gcb.12313
Subject(s) - environmental science , primary production , eddy covariance , ecosystem , carbon cycle , ecosystem respiration , carbon sink , atmospheric sciences , hydrology (agriculture) , sink (geography) , biomass (ecology) , ecology , geology , geography , geotechnical engineering , cartography , biology
Diagnostic carbon cycle models produce estimates of net ecosystem production ( NEP , the balance of net primary production and heterotrophic respiration) by integrating information from (i) satellite‐based observations of land surface vegetation characteristics; (ii) distributed meteorological data; and (iii) eddy covariance flux tower observations of net ecosystem exchange ( NEE ) (used in model parameterization). However, a full bottom‐up accounting of NEE (the vertical carbon flux) that is suitable for integration with atmosphere‐based inversion modeling also includes emissions from decomposition/respiration of harvested forest and agricultural products, CO 2 evasion from streams and rivers, and biomass burning. Here, we produce a daily time step NEE for North America for the year 2004 that includes NEP as well as the additional emissions. This NEE product was run in the forward mode through the CarbonTracker inversion setup to evaluate its consistency with CO 2 concentration observations. The year 2004 was climatologically favorable for NEP over N orth A merica and the continental total was estimated at 1730 ± 370 TgC yr −1 (a carbon sink). Harvested product emissions (316 ± 80 TgC yr −1 ), river/stream evasion (158 ± 50 TgC yr −1 ), and fire emissions (142 ± 45 TgC yr −1 ) counteracted a large proportion (35%) of the NEP sink. Geographic areas with strong carbon sinks included Midwest US croplands, and forested regions of the N ortheast, S outheast, and P acific N orthwest. The forward mode run with CarbonTracker produced good agreement between observed and simulated wintertime CO 2 concentrations aggregated over eight measurement sites around N orth A merica, but overestimates of summertime concentrations that suggested an underestimation of summertime carbon uptake. As terrestrial NEP is the dominant offset to fossil fuel emission over N orth A merica, a good understanding of its spatial and temporal variation – as well as the fate of the carbon it sequesters ─ is needed for a comprehensive view of the carbon cycle.