## 3 Results
### Seasonal Fluxes of Total CO\({}_{2}\)  
There were clear seasonal variations in total monthly SR, HR, and RR values (Figure 5). Distinct differences were observed between total monthly HR and RR. Particularly, impressive growth of total monthly RR has been observed from March to May, in contrast to the smooth increase in HR values during this period. The decline of soil CO\({}_{2}\) fluxes observed during the summer dry periods has led to a reduction in total SR and RR in these months, but has relatively weakly affected HR values. We observed significant correlations between total monthly SR values (n = 24) in both ecosystems (r = 0.84) and between total monthly HR values as well (r = 0.96). For total monthly RR values, the relationship between ecosystems studied was weaker (r = 0.57). For the formal analysis, we divided the year into two seasons: October-March and April-September. Two-way ANOVA indicated a likely interaction between ecosystem type and the seasonal factor for SR (\(p\) = 0.006), along with a formally nonsignificant effect of the ecosystem at the annual scale (\(p\) = 0.06). For HR, the analysis revealed no interaction between the ecosystem and the season (\(p\) = 0.59), while a significant ecosystem effect was observed (\(p\) = 0.0006). All possible combinations of ecosystem and seasonal factors were significant for RR (\(p\) \(<<\) 0.001). Therefore, seasonal differences in total month SR between the two ecosystems are caused mainly by the dynamics of RR flux (Figure 6a,c). The root component of total SR was notably higher in the grassland than in the forest between April and September, whereas it was similar in both ecosystems between October and March (Figure 5c). Alternate HR values were consistently higher in the forest than in the grassland during the entire year (Figure 5b). As with RR, the differences increased during the warm period, reflecting the response of HR to temperature increasing (Figure 6a). Figure 5: Dynamics of total monthly soil (SR), SOM-derived heterotrophs (HR), and root-derived (RR) respiration values (**a**–**c**) and their distribution over two years (**d**–**f**): the median (bar), lower (Q1) and upper (Q3) quartiles (“boxes”); X1 = Q1 – 1.5 IQR (interquartile range, IQR = Q3 – Q1) and X2 = Q3 – 1.5 IQR (“moustaches”); all data are shown as dots. Surprisingly, there were no clear seasonal dynamics of the shares of HR and RR in the total monthly SR in contrast to the differences between ecosystems (Figure 6b). However, a small yet significant relationship was found between the dynamics of HR contributions in the two ecosystems studied (Figure 6d). The annual shares of HR were 57-67% in the forest and 28% in the grassland with minor variation across seasons. In the grassland, the minimum of HR share was in the spring (17-19%) and the maximum in the summer (32-34%), comprising 26-37% during the autumn and winter periods. In the forest ecosystems, the maximum share of HR was registered in the summer (62-76%) and comprised 52-62% during all other seasons. Nevertheless, the changes in HR shares between the two years differed between the two ecosystems. In the grassland, the contribution of HR during the cold season increased from 27% in the first year to 40% in the second year. However, this dynamic did not lead to a change in the annual share of HR. In the forest, the share of HR during the warm season decreased year-to-year from 69% to 57%, which led to a decrease in the annual share of HR from 67% to 57%. The total annual SR flux was 1.3 times higher in the grassland compared to the forest for both years studied (Table 3). These differences were formed during a warm period (1.4-1.5 times higher), and especially during spring (1.6-1.9 times higher) when rapid RR growth was observed in the grassland. During the cold season, the alternate total SR was 1.2-1.3 times higher in the forest compared to grassland, due to the differences in HR values between the ecosystems.