Selected abundance ratios (indicated on top of each panel) as a function of time in simulations S1 to S3, labeled in the top right panel. Solid lines correspond to simulations where the N+C exchange reactions presented in Table 2 are excluded from the chemical network, while dashed lines show the corresponding results in the fiducial simulations that include all exchange reactions (reproducing data from Fig. 3). The dashed black line in each panel indicates either the assumed elemental ¹²C/¹³C or ¹⁴N/¹⁵N ratio, depending on the quantity being plotted.