Abstract Solar-induced fluorescence (SIF) has shown great promise for probing spatiotemporal variations in terrestrial gross primary production (GPP), the largest component flux of the global carbon cycle. However, scale mismatches between SIF and ground-based GPP have posed challenges toward fully exploiting thesedata. We used SIF obtained at high spatial sampling rates and resolution by NASAˈs… More

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Ecosystem-atmosphere fluxes of 12CO2 and 13CO2 are needed to better understand the impacts of climate and land use change on ecosystem respiration (FR), net ecosystem CO2 exchange (FN), and canopy-scale photosynthetic discrimination (Δ). We combined micrometeorological and stable isotope techniques to quantify isotopic fluxes of 12CO2and 13CO2 over a corn–soybean rotation ecosystem in the Upper… More

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Quantifying isotopic CO2 exchange between the biosphere and atmosphere presents a significant measurement challenge, but has the potential to provide important constraints on local, regional, and global carbon cycling. Past approaches have indirectly estimated isotopic CO2 exchange using relaxed eddy accumulation, the flask-based isoflux method, and flux-gradient techniques. Eddy covariance (EC) is an attractive method… More

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The oxygen isotope of water (18O-H2O) and carbon dioxide (18O-CO2) is an important signal of global change and can provide constraints on the coupled carbon-water cycle. Here, simultaneous observations of 18O-H2O (liquid and vapor phases) and 18O-CO2 were used to investigate the relation between canopy leaf water 18O enrichment, 18O-CO2 photosynthetic discrimination (18Δ), isotope disequilibrium… More

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The oxygen isotope composition of evapotranspiration (δF) represents an important tracer in the study of biosphere–atmosphere interactions, hydrology, paleoclimate, and carbon cycling. Here, we demonstrate direct measurement of δF based on the eddy-covariance and tunable diode laser spectroscopy (EC-TDL) techniques. Results are presented from laboratory experiments and field measurements in agricultural ecosystems. The field measurements… More

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Agricultural crops with a C4 photosynthetic pathway rapidly expanded across North America as early as 800 A.D. Their distribution continues to expand globally as demands for food and biofuel production increase. These systems are highly productive, having a significant impact on carbon and water exchange between the land and atmosphere. Here, we investigate the relative… More

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Agricultural ecosystems have been viewed with the potential to sequester atmospheric carbon dioxide (CO2) by increasing soil organic carbon (SOC) through reduced tillage and cover cropping practices. There remains considerable uncertainty, however, regarding the carbon (C) sink/source potential of these systems and few studies have examined C dynamics in conjunction with other important greenhouse gases…. More

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The stable carbon isotope ratio, , is a valuable tracer for studying the processes controlling the autotrophic (FRa) and heterotrophic (FRh) contributions to ecosystem respiration (FR) and the influence of photosynthesis on FR. There is increasing interest in quantifying the temporal variability of the carbon isotope composition of ecosystem respiration (δR) because it contains information… More

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There is much interest in the role that agricultural practices might play in sequestering carbon to help offset rising atmospheric CO2 concentrations. A number of management methods that might increase soil C levels have been suggested, but there are scant available data to properly support recommendations or policy changes. We have used eddy covariance measurements… More

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