## 3 Results
### Co\({}_{2}\) and \({}^{13}\)Co\({}_{2}\) Fluxes and Cumulative Emissions  
CO\({}_{2}\) fluxes from all litter treatments increased after onset of incubation compared to Control (Figure 1a,b, Supplementary Figure S3). Total CO\({}_{2}\) fluxes were highest in Leaf reaching 5.1 mg C kg\({}^{-1}\) h\({}^{-1}\) on 2 DAO. In Root, CO\({}_{2}\) flux peaked on 2 DAO (2.57 mg C kg\({}^{-1}\) h\({}^{-1}\)) and then decreased throughout the incubation period. In Straw, the highest CO\({}_{2}\) fluxes were measured directly after onset of incubation (2.8 mg C kg\({}^{-1}\) h\({}^{-1}\)), and continuously decreased afterwards. Litter-derived and SOM-derived CO\({}_{2}\) followed a similar pattern as total CO\({}_{2}\) fluxes and were highly correlated (adj. R\({}^{2}\) = 0.88, \(p\) < 0.001, Table 3). Highest litter-derived CO\({}_{2}\) fluxes were measured in Leaf on 3 DAO (3.0 mg C kg\({}^{-1}\) h\({}^{-1}\)), in Straw on 1 DAO (1.2 mg C kg\({}^{-1}\) h\({}^{-1}\)), and in Root on 2 DAO (1.7 mg C kg\({}^{-1}\) h\({}^{-1}\)) (Figure 1a). SOM-derived CO\({}_{2}\) was highest in Leaf and higher in all litter treatments compared to Control for the first week after onset of incubation (Figure 1b). Accordingly, the cumulative priming effect increased most strongly in all litter treatments during the first days of incubation (Figure 1c) with highest values in Leaf.  
Cumulative CO\({}_{2}\) emissions from all litter treatments were significantly higher than from Control without litter (\(p\) < 0.05, Table 4). The highest cumulative and litter-derived CO\({}_{2}\) emissions were measured after addition of maize leaves, followed by maize straw and maize roots; however, cumulative SOM-derived CO\({}_{2}\) emissions were higher than litter-derived CO\({}_{2}\) emissions in all treatments (Table 4). Total cumulative CO\({}_{2}\) emissions were significantly positively correlated with total C and water-soluble C input from maize litter (adj. R\({}^{2}\) = 0.80 and adj. R\({}^{2}\) = 0.90, respectively, \(p\) < 0.001, Table 3). When total cumulative CO\({}_{2}\) emissions were standardized against C input from litter, no differences were found (Supplementary Table S2).  
\begin{table}
\begin{tabular}{c c c c} \hline  & **Adjusted R\({}^{2}\)** & \(p\)**-Value** & **n** \\ \hline _Oxic incubation period_ & & & \\ Cumulative NO+N\({}_{2}\)O emissions \(\sim\) water-soluble litter C input & 0.4401 & 0.001172 & 19 \\ Cumulative N\({}_{2}\)O emissions \(\sim\) litter C:N ratio & 0.247 & 0.03428 & 15 \\ Cumulative NO emissions \(\sim\) water-soluble litter C:N ratio & 0.8703 & \(2.427\times 10^{-7}\) & 15 \\ Cumulative NO emission \(\sim\) net N mineralization & 0.5671 & 0.0001197 & 19 \\ NO+N\({}_{2}\)O flux \(\sim\) CO\({}_{2}\) flux & 0.08023 & \(<\)2.2 \(\times\)\(10^{-16}\) & 1715 \\ \hline _Anoxic incubation period_ & & & \\ Cumulative N\({}_{2}\) emissions \(\sim\) water-soluble litter C:N ratio & 0.2553 & 0.03158 & 15 \\ Cumulative NO+N\({}_{2}\)O+N\({}_{2}\) emissions \(\sim\) total litter C input & 0.5087 & 0.0003655 & 19 \\ N\({}_{2}\)O/(N\({}_{2}\)O+N\({}_{2}\)) ratio \(\sim\) water-soluble litter C:N ratio & 0.5061 & 1.886 \(\times\)\(10^{-6}\) & 19 \\ N\({}_{2}\)O/(N\({}_{2}\)O+N\({}_{2}\)) ratio \(\sim\) WEOC: NO\({}_{3}\)\({}^{-}\) ratio & 0.4127 & 0.0018 & 19 \\ NO+N\({}_{2}\)O+N\({}_{2}\) flux \(\sim\) CO\({}_{2}\) flux & 0.864 & \(<\)2.2 \(\times\)\(10^{-16}\) & 176 \\ \hline _Total incubation period_ & & & \\ Cumulative CO\({}_{2}\) emissions \(\sim\) total litter C input & 0.8974 & \(4.84\times 10^{-10}\) & 19 \\ Cumulative CO\({}_{2}\) emissions \(\sim\) water-soluble litter C input & 0.798 & \(1.606\times 10^{-7}\) & 19 \\ Litter-derived CO\({}_{2}\) flux \(\sim\) SOM-derived CO\({}_{2}\) flux & 0.8838 & \(<\)2.2 \(\times\)\(10^{-16}\) & 495 \\ \(\delta^{15}\)N\({}_{\rm NO3}\) of soil NO\({}_{3}\)\({}^{-}\)\(\sim\) net N mineralization (52 DAO) & 0.729 & \(<\)2.024 \(\times\)\(10^{-6}\) & 19 \\ \hline \end{tabular}
\end{table}
Table 3: Coefficients of determination and \(p\)-values for simple linear regressions.