Abstract. For the past decade, observations of carbonyl sulfide (OCS or COS) have been investigated as a proxy for carbon uptake by plants. OCS is destroyed by enzymes that interact with CO2 during photosynthesis, namely carbonic anhydrase (CA) and RuBisCO, where CA is the more important one. The majority of sources of OCS to the atmosphere are geographically separated from this large plant sink, whereas the sources and sinks of CO2 are co-located in ecosystems. The drawdown of OCS can therefore be related to the uptake of CO2 without the added complication of co-located emissions comparable in magnitude. Here we review the state of our understanding of the global OCS cycle and its applications to ecosystem carbon cycle science. OCS uptake is correlated well to plant carbon uptake, especially at the regional scale. OCS can be used in conjunction with other independent measures of ecosystem function, like solar-induced fluorescence and carbon and water isotope studies. More work needs to be done to generate global coverage for OCS observations and to link this powerful atmospheric tracer to systems where fundamental questions concerning the carbon and water cycle remain.

Abstract. For the past decade, observations of carbonyl sulfide (OCS or COS) have been investigated as a proxy for carbon uptake by plants. OCS is destroyed by enzymes that interact with CO 2 during 25 photosynthesis, namely carbonic anhydrase (CA) and RuBisCO, where CA is the more important. The majority of sources of OCS to the atmosphere are geographically separated from this large plant sink, whereas the sources and sinks of CO 2 are co-located in ecosystems. The drawdown of OCS can therefore be related to the uptake of CO 2 without the added complication of co-located emissions comparable in magnitude. Here we review the state of our understanding of the global OCS cycle and 30 its applications to ecosystem carbon cycle science. OCS uptake is correlated well to plant carbon uptake, especially at the regional scale. OCS can be used in conjunction with other independent measures of ecosystem function, like solar-induced fluorescence and carbon and water isotope studies.More work needs to be done to generate global coverage for OCS observations and to link this powerful Biogeosciences Discuss., https://doi

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Agriculture is historically a dominant form of global environmental degradation, and the potential for increased future degradation may be driven by growing demand for food and biofuels. While these impacts have been explored using global gridded maps of croplands, such maps are based on relatively coarse spatial data. Here, we apply high-resolution cropland inventories for the conterminous U.S. with a land-use model to develop historical gridded cropland areas for the years 1850-2000 and year 2000 abandoned cropland maps. While the historical cropland maps are consistent with generally accepted land-use trends, our U.S. abandoned cropland estimates of 68 Mha are as much as 70% larger than previous gridded estimates due to a reduction in aggregation effects. Renewed cultivation on the subset of abandoned croplands that have not become forests or urban lands represents one approach to mitigating the future expansion of agriculture. Potential bioenergy production from these abandoned lands using a wide range of biomass yields and conversion efficiencies has an upper-limit of 5-30% of the current U.S. primary energy demand or 4-30% of the current U.S. liquid fuel demand.

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Local food systems may facilitate agroecological practices that conserve nutrient, energy, and water resources. However, little is known about the potential for local food systems to scale beyond niche markets and meet a substantial fraction of total food demand. Here we estimate the upper potential for all existing US croplands to meet total US food demand through local food networks. Our spatially explicit approach simulates the years 1850 through 2000 and accounts for a wide range of diets, food waste, population distributions, cropland areas, and crop yields. Although we find that local food potential has declined over time, particularly in some coastal cities, our results also demonstrate an unexpectedly large current potential for meeting as much as 90% of the national food demand. This decline in potential is associated with demographic and agronomic trends, resulting in extreme pressures on agroecological systems that, if left unchecked, could severely undermine recent national policies focused on food localization. Nevertheless, these results provide a spatially explicit foundation for exploring the many dimensions of agroecosystem sustainability.

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Carbonyl sulfide (COS or OCS), the most abundant sulfur‐containing gas in the troposphere, has recently emerged as a potentially important atmospheric tracer for the carbon cycle. Atmospheric inverse modeling studies may be able to use existing tower, airborne, and satellite observations of COS to infer information about photosynthesis. However, such analysis relies on gridded anthropogenic COS source estimates that are largely based on industry activity data from over three decades ago. Here we use updated emission factor data and industry activity data to develop a gridded inventory with a 0.1° resolution for the U.S. domain. The inventory includes the primary anthropogenic COS sources including direct emissions from the coal and aluminum industries as well as indirect sources from industrial carbon disulfide emissions. Compared to the previously published inventory, we found that the total anthropogenic source (direct and indirect) is 47% smaller. Using this new gridded inventory to drive the Sulfur Transport and Deposition Model/Weather Research and Forecasting atmospheric transport model, we found that the anthropogenic contribution to COS variation in the troposphere is small relative to the biosphere influence, which is encouraging for carbon cycle applications in this region. Additional anthropogenic sectors with highly uncertain emission factors require further field measurements.