## 3 Results  
The annual trends in the mean basal area increment (BAI) for the three treatments in the mixed and pure stand were similar (Figure 2). However, tree growth was lower in the spring burned plots in the mixed stand than in the unburned and autumn burned plots (Figure 2a). Hence, the BAI was standardized and shown in box plots per type of stand (mixed or pure) for the comparison of tree growth (Figures 3 and 4). In both stands, tree growth was lower after spring burning (Figures 3 and 4). The same trend of slight reduction on tree growth was observed in the pure stand one year after autumn burning (Figure 4). Conversely, in the mixed stand, a scarce impact on tree growth was shown in the year following autumn burning (Figure 3). The type of stand (mixed or pure) did not have an influence on tree growth (Table 5). The tree variables, percentage of live crown height and diameter at breast height, were significant factors in the three models (although the percentage of live crown height in Model NB was not significant; \(p<0.1\)) (Table 5). Regarding the fire severity variables at the tree and stand level (maximum scorch height, time during which temperature in the cambium area was higher than 60 \({}^{\circ}\)C, time during which temperature in the bark surface was higher than 300 \({}^{\circ}\)C and litterfall biomass), the maximum scorch height was a significant factor (Model SB and AB). A higher scorch height is related to a greater fire severity, which may negatively influence tree growth. The time during which the temperature in the bark surface was higher than 300 \({}^{\circ}\)C was only significant in Model SB, as well as t60, which was significant in the same model. In this sense, the spring burning appeared to have a greater effect on tree growth than the autumn burning. The values of the variables related with the residence time above lethal temperatures did not have an impact on the autumn burning due to the low intensity of the fire. Litterfall was not a significant factor in any of the models. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**S** & **PT** & **H** & **Hc** & **DBH** & **SMx** & **t60** & **t300** & **L16** & **L17** \\ \hline
**–** & **–** & **m** & **\%** & **cm** & **cm** & **s** & **s** & **kg ha\({}^{-1}\)** & **kg ha\({}^{-1}\)** \\ \hline Mixed & No & 12.2 & 50.3 & 19.5 & – & – & – & 3171 & 3532 \\ stand & burning & (5.0) & (16.2) & (10.3) & – & – & (649) & (585) \\ \hline Mixed & Spring & 11.9 & 48.0 & 18.1 & 54 & 31 & 10 & 3257 & – \\ stand & burning & (5.0) & (15.2) & (10.0) & (50) & (82) & (26) & (599) & – \\ \hline Mixed & Autumn & 12.2 & 50.1 & 19.4 & 46 & 16 & 6 & – & 2732 \\ stand & burning & (5.2) & (15.8) & (10.4) & (45) & (59) & (20) & (325) \\ \hline Pure & No & 13.1 & 39.4 & 19.6 & – & – & – & 1989 & 2393 \\ stand & burning & (4.9) & (14.4) & (10.1) & – & – & – & (519) & (739) \\ \hline Pure & Spring & 13.9 & 37.9 & 19.5 & 167 & 23 & 44 & 3482 & – \\ stand & burning & (4.4) & (15.1) & (9.4) & (201) & (93) & (167) & (129) & – \\ \hline Pure & Autumn & 14.5 & 36.2 & 21.7 & 132 & 16 & 33 & – & 3629 \\ stand & burning & (5.3) & (12.5) & (11.3) & (169) & (81) & (149) & – & (527) \\ \hline \hline \end{tabular}  
\(\mathbb{S}\): type of stand; PT: plot treatment; H: tree height; Hc: percentage of live crown height; DBH: diameter at breast height; SMx: maximum scorch height; t60: time during which the temperature in the cambium area was higher than 60 \({}^{\circ}\)C; t300: time during which the temperature in the bark surface was higher than 300 \({}^{\circ}\)C; L16: litterfall biomass from May 2016 to April 2017; L17: litterfall biomass from November 2016 to October 2017. Standard deviation in brackets.  
\end{table} 
Table 4: Main variables used to model the impact of prescribed burning on tree growth. Figure 2: Comparison of annual trends in mean basal area increment (BAI) in (**a**) the mixed stand and in (**b**) the pure stand. Unburned plots (solid line), spring-burned plots (dashed line) and autumn-burned plots (dotted line).