## 3 Results and Discussion  
### Choice of the \(R_{0}\)  
One of the key parameters of all the empirical models described above is \(R_{0}\)--the soil respiration at 0 \({}^{\circ}\)C. It significantly affects the modeling quality because it defines the low boundary of the modeling data (winter periods) and the intercept with the ordinate axis of the linear model (lm), comparing modeling and measured data. In the ideal model, the intercept of lm should lay in the origin of the coordinate system and the slope of lm should be equal to 1. However, as a rule for the real models, the slope \(<\) 1 and intercept \(>\) 0 due to an insufficient magnitude of the modeled data in comparison with the measurements--the extreme values are not represented well by the modeling [20; 31; 42]. In our research, \(R_{0}\) was estimated from modeling by the T-TPP-TPC-TPPC models in the following way: \(R_{0}\) is directly interconnected with the intercept of lm and by controlling and lowing \(R_{0}\), the intercept of lm is being readjusted to become positive and closer to zero and at the same time, the slope of lm increases and becomes closer to unity. With the negative intercept of lm, there will be an underestimation of the soil respiration in the winter periods. The obtained \(R_{0}\) values (colored lines, Figure 3) are two-three times smaller than the earlier obtained values by [PERSON] (1995)[PERSON] (1995) and [PERSON] et al. (2020)[PERSON] et al. (2020) for the Entic Podzol. They can be directly compared with the SR measurements at \(0\leq T_{soll}<1\)\({}^{\circ}\)C in the autumn-winter period (colored dots with labels, Figure 3) when there is not any freezing of the top-soil level, and by the selection of the temperature interval, they should be located closer to the lower SR observed at the lower temperatures (\(T_{soll}\approx 0\)). Figure 3: Parameter \(R_{0}\)—soil respiration in autumn–winter period, \(T_{soll}\approx 0\)\({}^{\circ}\)C—values (colored horizontal lines) obtained during modeling by T–TP–TP–TPC–TPPC models (intercept \(\rightarrow\) 0+) with the parameterization by the soil temperature (**top**) and the air temperature (**bottom**, monitoring station) in the normal (green line), wet (blue line), and dry (brown line) years; colored dots with labels—individual SR measurements, where the labels are the measurement-month numbers and the dot colors for the monthly-precipitation amount are red (\(11<P<34\) mm), brown (\(34<P<57\) mm), yellow (\(57<P<80\) mm), green (\(80<P<103\) mm), and blue (\(103<P<126\) mm). As the result of such a selection (intercept \(\rightarrow\) 0+), the \(R_{0}\) values obtained for the different set of years--normal (n), wet (w), and dry (d)--demonstrate a weak linear dependency from the soil moisture (colored lines, Figure 3) with the minimal \(R_{0}\) values corresponding mainly with the dry period (brown lines). These \(R_{0}\) maximize the slope of lm (see Tables 1-4 in the Appendix A) as well. It should be noted that the \(R_{0}\) values obtained from the models parameterized by \(T_{air}\) are about 15% higher than the values obtained from the models parameterized by \(T_{soil}\). This observation can be explained from the differences between \(T_{air}\) and \(T_{soil}\) for these conditions: the average soil temperature (\(T_{soil}\approx\) 2 \({}^{\circ}\)C, brown vertical line, Figure 4) is about two degrees higher than the simultaneously observed air temperature (\(T_{air}\) = 0 \({}^{\circ}\)C, blue horizontal line, Figure 4), which is associated with the more intensive SR for \(T_{air}\) = 0 \({}^{\circ}\)C than for \(T_{soil}\) = 0 \({}^{\circ}\)C.  
The \(R_{0}\) values obtained for different conditions (colored horizontal lines, Figure 3) are close to each other when the parameterization with \(T_{soil}\) was done.