The effectiveness of policies and management actions in reducing the release of excess nitrogen (N) to the environment is best assessed if N fluxes across air, land, and water are regularly quantified at relevant scales. Here we compiled 2002, 2007, and 2012 inventories of inputs and nonhydrologic N outputs along with fossil fuel emissions, food demand, and terrestrial N surpluses for all subbasins of the contiguous United States using peer‐reviewed, publicly available data sets. We found that at the national scale, total inputs, outputs, and surpluses changed little (±6%) between 2002 and 2012 and remained dominated by agricultural processes, despite efforts to curb N losses. This consistency at the national scale, however, obscured large counteracting shifts at regional levels driven by variable fluxes across regions. Throughout the eastern United States, declines in deposition and fertilizer inputs combined with increased crop yields resulted in a decrease in terrestrial N surpluses, which may explain recent water quality improvements in the region. On the other hand, fertilizer N inputs in the Midwest increased at a greater rate than crop harvest N increased, leading to a larger terrestrial surplus N. A large relative increase (~320%) in N emissions in the West due to an unusual wildfire season in 2012 was also observed. These changes coincided with national policies that decreased N emissions and increased demand for domestic biofuels, potentially highlighting the capacity to change the source and magnitude of N inputs and fluxes across the landscape through market and regulatory actions.

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Wind is a persistent force in arid and semiarid lands. Microphytic crusts have been attributed with the ability to reduce wind erosion because of soil binding qualities. The purpose of this research was to determine if microphytic crusts contribute to soil stability in an arid land setting. Threshold friction velocity is the wind speed necessary for the initiation of soil erosion and, thus, is a measure of soil surface stability. A portable wind tunnel was used to determine threshold friction velocity on soil surfaces consisting of microphytic crusts living and undisturbed (control), chemically killed microphytic crusts but otherwise undisturbed (chemically killed), and microphytic crusts mechanically removed from the soil surface (scalped) to approximate conditions of absence. Significantly lower threshold friction velocities were measured within the scalped treatment than in the control or chemically killed treatments. Threshold friction velocities were not significantly different among control and chemically killed treatments. Significantly more wind-eroded material, entrained in the airstream and trapped by an inline filter, was obtained from the scalped treatment than from chemically killed or control treatments. Additionally, wind erosion occurred at significantly lower wind speeds in the scalped treatment. Microphytic crusts helped contribute to soil stability by binding soil particles, mainly by linked strands of cyanobacteria. Additional designed experiments are warranted to determine how the stabilizing influence of microphytic crusts are affected by type, degree, frequency, and season of disturbance and to answer pragmatic questions of concern to managers, such as determining acceptable levels of crust disruption and the wind speeds associated with erosion.