## 4 Discussion  
In the Mediterranean environment, where the frequency of wildfires is high, it is useful to understand the impact of fires on soil microbial properties in order to prevent them and to put into practice strategies aiming to recover burnt areas. By now, it is known that fire effects on soils depend on fire intensity and frequency, but also on vegetation type, climate, fuel load, and topographic characteristics [37; 38; 39]; fire's effects on soil activities have been investigated to a lesser extent and the results of these studies are still controversial. In the present research, the enzymatic activities mainly varied according to the vegetation covers, the seasons, and to a lesser extent according to the fire, as well as depending on the variations of soil abiotic properties [40; 41]. In particular, in soils under the same vegetation cover the enzymatic activities were controlled by different soil properties according to seasons and fire occurrence, as shown by the multiple linear regressions. In fact, for all the vegetation covers, HA, DHA, and \(\beta\)-GLU activities over the seasons were controlled only by nutrient availabilities; whereas, in burnt soils they were also controlled by pH, contents of water, and organic matter, C and N, and by Al, Cu, and Pb availabilities. Seasonality exerted a strong effect on nutrient availabilities [42]; whereas, fire occurrence, besides its influence on nutrient and metal availabilities [14], also caused variations in soil pH, organic matter, and C and N contents [43]. These profound changes in soil abiotic properties, due to seasonality and fire effects, affected soil microbial and enzymatic activities [44]. However, some differences in properties affecting the enzymatic activities occurred among soils under the different investigated vegetation covers. More specifically, the availability of different macro- and micro-nutrients (i.e., Ca, Fe, K, Mg, Mn, and Na) regulated the temporal variation of each enzymatic activity in soils under different vegetation covers. This could be due to the heterogeneity of nutrient availability over the seasons under the same vegetation cover. For instance, Mg and Na significantly varied over the seasons in soils under all the investigated vegetation covers even if the highest values were frequently detected in fall. The high values of macronutrients found in fall could be due to the reduction in the plant uptake and nutrient requirements, and to the high litter accumulation that enhance the decomposition process [42]. Soils under pine showed differences in temporal variation of nutrient availability, as compared with the other vegetation covers, as the lowest values of Ca was detected in winter and those of Mn in summer, suggesting that, for this species, a temporal shift related to request of these elements occurred [45]. As observed for macro- and micro-nutrients, metals (i.e., Al, Cu, and Pb) also significantly varied over the seasons in soils under all the investigated vegetation covers, with the exception of Pb,which did not significantly vary under herbs. Despite of nutrients, metals showed similar temporal trends with the highest values in winter and the lowest in summer, suggesting that their mobility is more affected by microclimatic conditions rather than plants and uptake [32]. In addition, the pollution effect that is marked in winter when the anthropic activity is greater cannot be excluded [46]. The temporal variations in each enzymatic activity showed significant variations only for HA in soils under HO and BL, and for DHA in soils under P. It is most likely that these variations for HA were due to C and N concentrations and to nutrient availability, especially Ca, K, and Mg, and for DHA were due to Ca and K availability. Hydrolytic enzymes are a reliable index of soil bioactivity and fertility due to the association of humus and C and N contents [47].