Carbon dioxide concentration and flux in a large agricultural region of the great plains of North America

Abstract

Results of observations of CO2 concentration [CO2] and flux in an area of typical agricultural land use in the east central Great Plains of North America (Mead, Nebraska) are reported. The observations were made at sufficient heights to represent an integration of CO2 fixation and release due to all types of land use in the region (pasture, alfalfa, annual crops). Minimum daytime [CO2] ranges from about 295–300 ppm in late July to early August (the time of apparent maximum photosynthetic activity) to 328–332 ppm in winter. The shape of the annual CO2 concentration cycle at Mead is described and compared with those for Mauna Loa, Hawaii, and Barrow, Alaska. Peak daytime flux of CO2 (in g×10−7 cm−2 s−1) from the atmosphere to the ground varied from about 0.5 in early June to 1.5–2.0 in late July to early August and 0.5 in late September. The net daily CO2 flux (in grams per square meter), calculated from the downward daytime and upward nocturnal fluxes, is about 10–12 in early June, 18–20 in early August (maximum), 6–10 in September, and 1–5 in early October.