Carbon monoxide fluxes from natural, managed, or cultivated savannah grasslands

Journal Article · Sat Aug 20 04:00:00 EDT 1994 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/93JD02918· OSTI ID:98833

Sanhueza, E; Donoso, L ^[1]; Scharffe, D; Crutzen, P J ^[2]

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1. Instituto Venezolano de Investigaciones Cientificas, Caracas (Venezuela)
2. Max-Planck-Institut fuer Chemie, Mainz (Germany)

As part of a comprehensive study on tropical land use change and its effect on atmospheric trace gas fluxes, we report the CO fluxes recorded at a natural grassland site and the changes produced when this ecosystem was managed or cultivated. The field site is located in the central part of the savannah climatic region of Venezuela. Fluxes were measured in the dark using the enclosed chamber technique. CO was analyzed with a reduction-gas detector in combination with a molecular sieve 5A column for CO separation. At all sites, CO fluxes exhibited a strong diurnal variation, with net emission during daytime and consumption or no fluxes during nighttime. In unplowed soils no differences were observed between dry and rainy season. A large disparity was observed between unplowed and plowed grassland soils. Plowed soil shows a much smaller emission during daytime and a larger consumption at night. The 24-hour integrated fluxes indicate that the nonperturbed grassland switches from being a net source of CO (3.4 x 10{sup 10} molecules cm{sup {minus}2} s{sup {minus}1}) to being a net sink (-1.6 x 10{sup 10} molecules cm{sup {minus}2} s{sup {minus}1}) after plowing. It is likely that burial of surface litter reduces the production of CO in the top soil and that the diffusion of CO to deeper layers (where CO is consumed by microbiological processes) is promoted in decompacted soils. As the rainy season progressed the plowed soil gradually compacted and CO fluxes changed back, and after 3 months the fluxes from plowed soils and the original unplowed soils were equal. Even though the various cultivated fields (corn, sorghum, and pasture) received differing inorganic fertilization treatments, no significant difference in the CO fluxes resulted. Measurements during the dry season suggest that {open_quotes}degrading dry (dead) vegetation{close_quotes} produces CO under dark conditions. 14 refs., 5 figs., 3 tabs.

• OSTI ID: 98833
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: D8 Vol. 99; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
AEROSOL MONITORING
CARBON MONOXIDE
EARTH ATMOSPHERE
EMISSION
ENVIRONMENTAL TRANSPORT
GREENHOUSE GASES
RANGELANDS
VENEZUELA