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Deep Unsaturated Zone Contributions to Carbon Cycling in Semiarid Environments

Journal Article · · Journal of Geophysical Research. Biogeosciences
DOI:https://doi.org/10.1029/2018JG004669· OSTI ID:1479368
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  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth and Environment Sciences Area
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Understanding terrestrial carbon cycling has relied primarily on studies of topsoils that are typically characterized to depths shallower than 0.5 m. At a semiarid site instrumented down to 7 m, here we measured seasonal- and depth-resolved carbon inventories and fluxes and groundwater and unsaturated zone flow rates. Measurements showed that ~30% of the CO2 efflux to the atmosphere (60% in winter) originates from below 1 m, contrary to predictions of less than 1% by Earth System Model land modules. Respiration from deeper roots and deeper microbial communities is supported by favorable subsurface temperatures, moisture, and oxygen availability. Below 1 m, dissolved organic carbon fluxes from the overlying soil and C from deep roots and exudates are expected to be important in sustaining microbial respiration. Finally, because these conditions are characteristic of semiarid climate regions, we contend that Earth System Model land modules should incorporate such deeper soil processes to improve CO2 flux predictions.
Research Organization:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE; USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Grant/Contract Number:
AC02-05CH11231
OSTI ID:
1479368
Alternate ID(s):
OSTI ID: 1472185
Journal Information:
Journal of Geophysical Research. Biogeosciences, Journal Name: Journal of Geophysical Research. Biogeosciences Journal Issue: 9 Vol. 123; ISSN 2169-8953
Publisher:
American Geophysical UnionCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (2)

Microbial communities across a hillslope‐riparian transect shaped by proximity to the stream, groundwater table, and weathered bedrock journal May 2019
Depth‐ and Time‐Resolved Distributions of Snowmelt‐Driven Hillslope Subsurface Flow and Transport and Their Contributions to Surface Waters journal November 2019

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Related Subjects

54 ENVIRONMENTAL SCIENCES
DOC flux
ESM land modules
carbon cycling
carbon fluxes
deep unsaturated zone
semiarid environments