## 3 Results
### Percentage Fuel Consumption in the Duff Layer  
Less than 50% by volume of all the duff layer samples from the control zone (C 0-5) were consumed. At moisture levels between 0% and 5%, in two samples from F 0-5 more than 60% by volume were consumed. The samples corresponded to D\({}_{24}\) from T5 with 63.4% and 60.67% consumption for 0% and 5% MC, respectively; and sample D\({}_{40}\) from T6 with 93.06% and 90.32% for 0% and 5% MC, respectively. At a moisture level between 10% and 25%, only in sample D\({}_{40}\) from T6 was more than 60% of the material consumed. At a moisture content between 5% and 10%, samples from the duff layer combust in 100% of the cases, with a mean consumption of each sample of 90.76 \(\pm\) 10%, 88.51 \(\pm\) 10% and 86.10 \(\pm\) 11%, respectively (Figure 8). \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \(B\) & \(SE\) & \(t\) & \(p\)**-Value** \\ \hline (Constant) & 1.499 & 0.122 & 12.312 & 0.000 \\ IM (\%) & –0.010 & 0.003 & \(-\)3.264 & 0.002 \\ BD (kg/m\({}^{3}\)) & –0.001 & 0.000 & \(-\)2.899 & 0.006 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Results of the linear regression analysis between the maximum P50 moisture limit, with the bulk density (BD) and the inorganic content (IM): \(R^{2}\) = 0.763, \(N\) = 20. Figure 7: (a) Linear regression (Table 6) between the moisture content (MC) at a 50% probability of ignition (P\({}_{50}\)), the bulk density (BD) and inorganic matter (IM). \(R^{2}\) = 0.763, \(et\) = 0.24, \(N\) = 20. (b) Relationship between moisture content at P\({}_{50}\), bulk density and organic matter (OM). The triangles represent density and the points represent IM or OM, \(N\) = 20. At 25% MC, the mean rate of consumption is 78.20 \(\pm\) 12%. At 50% MC, 73.33% of the samples continue to combust more than 60% of their organic content. For samples that can maintain combustion (\(<\)60%), the mean consumption is 76.05 \(\pm\) 12% of the sample. At 100% MC, all the samples do not exceed 60% consumption and they are unable to sustain smouldering combustion. The mean at this humidity results in a consumption of 37.16 \(\pm\) 12% of each sample (Figure 9). As for the percentage consumption of the duff horizon in relation to the mean transect slope, it can be seen that it is directly proportional over the first 24 m (\(D_{24}\)). From \(D_{0}\) (0 m) to \(D_{24}\) (24 m), the percentage of consumption decreases as the altitude gradient falls. Between \(D_{24}\) and \(D_{32}\), percentage consumption rises again. Figure 10a and Table 8a show the regression line that expresses the percentage of samples consumed at 90-100% according to their percentage humidity. The regression has a very high coefficient of determination (\(R^{2}\) = 0.919) and a high magnitude (\(F\) = 34.09, \(p\) \(<\) 0.01). The regression line can be expressed as:  
\[Cons_{90}=49.28-1.21\times MC\ (\%) \tag{4}\]  
Figure 8: Relationship between the % of the sample consumed with distance along the transect to different percentages of humidity, \(N\) = 48. (**a**) MC = 0%; (**b**) MC = 5%. Blue: duff or organic stratum (Oe + Oa); green: control area 0–5 cm; and grey: post-fire zone at 0–5 cm. Figure 9: Relationship between the % of the sample consumed with distance along the transect to different moisture levels, \(N\) = 15. (**a**) MC = 25%; (**b**) MC = 50% and (**c**) MC = 100%. where \(Cons_{90}\) is the percentage of samples of which more than 90% is consumed and \(MC\) (%) is the respective soil moisture content. This line seeks to provide an estimate of the maximum humidity limit so between 90% and 100% of each sample is consumed, which means that smouldering combustion can propagate easily. At rates of soil moisture between 5% and 15%, it is estimated that between 35% and 40% of the samples will be consumed more than 90% of their organic content. At 25% MC, the number of samples falls to 20%. Figure 10b and Table 8b show the linear regression models of the percentage of samples consumed \(>60\%\) according to humidity.