Air pollution from industrial and transportation sources declined across much of the United States during the COVID-19 pandemic. This provided an opportunity to examine whether brief reductions in nitrogen pollution to terrestrial ecosystems could alter carbon and nitrogen cycling in soils.  Scientists from USGS, state agencies, and multiple universities collected soils from forests, grasslands, and residential yards across 14 regions of the contiguous United States, and quantified soil carbon, nitrogen, and microbial properties in relation to atmospheric nitrogen deposition.  Soil carbon strongly influenced soil nitrogen cycling and microbial activity.  However, these relationships differed for sites with historically high nitrogen deposition, and this difference persisted even when nitrogen pollution declined during the 2020 COVID-19 pandemic. These findings indicate that long-term nitrogen pollution has caused persistent changes in soil microbial nitrogen cycling that are not readily reversed by temporary reductions in nitrogen pollution.   

Nieland, M.A., Lacy, P., Allison, S.D., Bhatnagar, J.M., Doroski, D.A., Frey, S.D., Greaney, K., Hobbie, S.E., Kuebbing, S.E., Lewis, D.B., McDaniel, M.D., Perakis, S.S., Raciti, S.M., Templer, P.H., Shaw, A.N., Sprunger, C.D., Strickland, M.S., Vietorisz, C., Ward, E.B., and Keiser, A.D., 2024, Nitrogen deposition weakens soil carbon control of nitrogen dynamics across the contiguous United States: Global Change Biology, v. 30, no. 12, e70016. https://doi.org/10.1111/gcb.70016