Legacy effects of increased temperature on both nitrogen (N) transformation rates and nitrous oxide (N2
O) emissions from permanent temperate grassland soil were evaluated. A new source-partitioning model showed the importance of oxidation of organic N as a source of N2
O. Gross organic (and not inorganic) N transformation rates decreased in response to the prior soil warming treatment. This was also reflected in reduced N2
O emissions associated with organic N oxidation and denitrification.