Nitrifier controls on soil NO and N2O emissions in three chaparral ecosystems under contrasting atmospheric N inputs

Nitrogen saturation theory predicts high rates of atmospheric N deposition can increase ecosystem N availability and stimulate ecosystem N losses via soil nitric oxide (NO; an air pollutant at high concentrations) and nitrous oxide (N2O; a strong greenhouse gas) emissions. However, it remains unclear whether theories developed in mesic ecosystems apply to drylands, where plant and soil N availability are not always coupled in dry soils. NO and N2O are often produced in soils during the oxidation of ammonia by ammonia oxidizing archaea (AOA) or ammonia oxidizing bacteria (AOB) during nitrification. AOB are thought to emit more NO and N2O during nitrification than AOA and may be favored in N-rich relative to N-limited environments, suggesting high rates of atmospheric N deposition might produce positive feedback sending more of the N to the atmosphere. To assess how high rates of atmospheric N deposition affect AOB- and AOA-derived N trace gas emissions, we selectively inhibited AOA and A..., Study Site
We collected soils from three sites exposed to a range of atmospheric N deposition rates in southern California: a Low N deposition site and two high N deposition sites (hereafter, High N1 and High N2; Table 1; EPA, 2021). Vegetation in all sites was dominated by chamise (Adenostoma fasciculatum). Soils from the Low N site are fine sandy loams from the Sheephead series and are classified as shallow Entic Haploxerolls. Soils from the High N1 site are coarse loams from the Shepherdsaddle series and are classified as Ultic Haploxeralfs. Finally, soils from the High N2 site are fine sandy loams from the Trigo series and are classified as shallow Typic Xerorthents (Table S1; Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture, 2019). The climate at all sites is Mediterranean with hot, dry summers and cool, wet winters. Annual precipitation ranges from 500 to 670 mm and average monthly temperatures range from 8 to 40°C.
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[https://doi.org/10.5061/dryad.xpnvx0kp0](https://doi.org/10.5061/dryad.xpnvx0kp0)

This dataset includes the data presented in the manuscript: \"Nitrifier controls on soil NO and N2O emissions in three chaparral ecosystems under contrasting atmospheric N inputs\". Briefly, we collected soils from the chaparral ecosystems in southern California and measured NO and N2O emissions from nitrification and denitrification. We treated soils with nitrification inhibitors to assess the relative contribution of ammonia-oxidizing bacteria (AOB) versus ammonia-oxidizing archaea (AOA) to N trace gas emissions. We also measured inorganic N pools to asses net rates of nitrification and net N mineralization. All soils were wet to 100% water holding capacity and were allowed to dry during the 46-hour incubation period. Finally, we present data on the abundance of AOA and AOB n...