## 1 Introduction
These changes could affect the fire regimes by increasing the dry, decomposed fuel accumulation leading to a larger number of smouldering fires and re-ignitions. At the local level, the annual temperature trend (1950-2015) in the study area is + 0.24 \({}^{\circ}\)C/decade, winter + 0.17 \({}^{\circ}\)C/decade, spring + 0.25 \({}^{\circ}\)C/decade, summer + 0.35 \({}^{\circ}\)C/decade and autumn + 0.19 \({}^{\circ}\)C/decade. The indicator of duration of the warm spell (IDWS) and the indicator of duration of the season of growth (IDSG) present a statistically significant positive trend, with an increase of 2.9 days/decade [18]. These changes in temperature extremes in the two seasons when the risk of fires is highest (spring and summer) may, in the future, result in an increase in the number of fires and changes in the fire regime [19]. The increase in drought conditions and the water deficit in spring and summer are likely to cause greater risks of forest fires [19]. According to forecasts made by [PERSON] et al. [20] and [PERSON] et al. [21] and described by [PERSON] et al. [14] for the Mediterranean-continental climate zone, the mean annual temperature will increase by + 0.7 [+ 0.5 / + 1] \({}^{\circ}\)C in 2021. This increase would be greater in summer (+ 0.9 [+ 0.5 / + 1.5] \({}^{\circ}\)C) than in the other seasons. Annual precipitation would vary significantly, with a possible increase of + 0.7 [- 14.1 / + 8] %, but it could vary seasonally, with an increase in winter, but with losses in the other seasons of the year. All these projected changes would have a major impact on the already scarce water resources of the zone. The duff's bulk density, porosity and organic composition are other important properties that have a direct impact on the ignition and propagation of smouldering fires [4]. The bulk density directly influences the fire ignition and extinction properties of organic matter, the critical moisture for extinction is higher than the critical moisture for ignition [22]. In addition, the bulk density influences the depth of combustion and the critical moisture threshold for extinction, since it regulates the oxygen supply, permeability and thermal inertia [22; 23]. The use of models that analysed combustion characteristics have been used in different ecosystems but in few cases for the Mediterranean ecosystem [1; 3; 7; 9]. Soil characteristics and its changes and effects in these combustion characteristics have been analysed inn various manuscripts [6; 8; 22; 23] but in any of them the soil analysed properties are in none of them was the number of soil variables analysed so high, giving this study a very high value and representativeness. In the Mediterranean region, smouldering combustion has been little studied as in general the region's soils have low levels of organic matter accumulation. However, in the Mediterranean soils that do accumulate organic layers, the relevant impacts of smouldering include the break-out of new flaming fires, the release of carbon from the soil into the atmosphere and the release of C stored in the soil's organic matter [7]. The particular case study of the Rocallaura Fires, also bring to light the need to bridge the gap between science and management. During the fire season in the Mediterranean region, the emergency response system is highly stress attending the several fires that break out continuously. Every fire emergency needs to be dealt efficiently with the minimum resources and time, especially if there is risk of simultaneous fire events that could stress the system even more [24]. The fact, that the Rocallaura fires had organic soils smouldering, required extra efforts from the Catalan Fire and Rescue Service forest fire units to control the smouldering fire that finally reignited a flammable fire jeopardising the organisation's efficiency and finally impacting on population at risk. Better understanding the behaviour of smouldering fires in Mediterranean organic soils, contributes towards better informed science-based decisions in fire management.