Releases of the greenhouse gases carbon dioxide (CO2) and methane (CH4) from thawing permafrost are expected to be among the largest feedbacks to climate from arctic ecosystems. However, the current net carbon (C) balance of terrestrial arctic ecosystems is unknown. Recent studies suggest that these ecosystems are sources, sinks, or approximately in balance at present…. More
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
Discrepancies in closure of the surface energy balance is often an issue for many land surface types. The role of canopy storage terms from canopy water content and photosynthesis is usually neglected in the surface energy balance of crops. Data from a research flux tower in central Illinois were used to evaluate these storage terms… More
Continuous measurements of carbon flux from 1997 to 2002 by eddy-covariance were used to evaluate the carbon budget for a maize (Zea mays L.) and soybean (Glycine max (L.) Merr.) rotation agricultural ecosystem that has been in no-till cultivation for over 14 years. These measurements were used to determine the net ecosystem exchange of carbon… More
Mitigating or slowing an increase in atmospheric carbon dioxide concentration ([CO2]) has been the focus of international efforts, most apparent with the development of the Kyoto Protocol. Sequestration of carbon (C) in agricultural soils is being advocated as a method to assist in meeting the demands of an international C credit system. The conversion of… More
Vegetation light use efficiency is a key physiological parameter at the canopy scale, and at the daily time step is a component of remote sensing algorithms for scaling gross primary production (GPP) and net primary production (NPP) over regional to global domains. For the purposes of calibrating and validating the light use efficiency (εg) algorithms,… More
This paper discusses the advantages and disadvantages of the different methods that separate net ecosystem exchange (NEE) into its major components, gross ecosystem carbon uptake (GEP) and ecosystem respiration (Reco). In particular, we analyse the effect of the extrapolation of night-time values of ecosystem respiration into the daytime; this is usually done with a temperature… More