Gill, A. L.; Grinder, R. M.; See, C. R.; Chapin, F. S.; DeLancey, L. C.; Fisk, M. C.; Groffman, P. M.; Harms, T.; Hobbie, S. E.; Knoepp, J. D.; Knops, J. M. H.; Mack, M.; Reich, P. B.; Keiser, A. D. 2023. Soil carbon availability decouples net nitrogen mineralization and net nitrification across United States Long Term Ecological Research sites. Biogeochemistry. 162(1): 13-24. doi:https://doi.org/10.1007/s10533-022-01011-w
Autotrophic and heterotrophic organisms require resources in stoichiometrically balanced ratios of carbon (C) to nutrients, the demand for which links organismal and ecosystem-level biogeochemical cycles. In soils, the relative availability of C and nitrogen (N) also defines the strength of competition for ammonium between autotrophic nitrifiers and heterotrophic decomposers, which may influence the coupled dynamics between N mineralization and nitrification. Here, we use data from the publicly available US National Science Foundation funded Long Term Ecological Research (LTER) network to evaluate the influence of soil C concentration on the relationship between net nitrification and net N mineralization. We found that soil C availability constrains the fraction of mineralized N that is ultimately nitrified across the continental gradient, contributing to reduced rates of nitrification in soils with high C concentrations. Nitrate, which is produced by nitrification, is a highly mobile ion that easily leaches to aquatic ecosystems or denitrifies into the greenhouse gas nitrous oxide (N2O). Understanding the connection between soil C concentration and soil N transformations is thus important for managing potential ecosystem N losses, understanding the biogeochemical constraints of these losses, and accurately representing coupled C-N dynamics in ecosystem models.