Prescribed fire is commonly used to reduce the wildfire risk in Mediterranean forests, but the soil’s hydrological response after fire is contrasting in literature experiences. The mulch treatment can limit the increases in runoff and erosion in the short term after a fire. The use of fern is preferable to straw, due its large availability in forests. However, no experiences of post-fire treatment with fern mulch have been found in the literature and therefore the mulching effectiveness has not been evaluated. This study has measured water infiltration rate (IR) and water repellency (SWR) using a rainfall simulator in three Mediterranean forest stands (pine, oak and chestnut) of Calabria (Southern Italy) after a prescribed fire and mulching treatment with fern in comparison to unburned soil. Prescribed fire reduced water infiltration in all forests in the short term compared to the unburned conditions, and increased SWR in pine and oak forests. These reductions in IR in the time window of disturbance after fire increased the runoff generation capacity in all soils, but had a lower effect on peak flows. However, soil mulching with fern limited the runoff rates and peak flows compared to the burned soils, but this treatment was less effective in pine forest. One year after fire, IR increased in burned soils (treated or not) over time, and SWR disappeared. The effects of mulching have disappeared after some months from fire. The study confirms the usefulness of mulching in broadleaves forest in the short term, in order to control the hydrological effects of prescribed fire in Mediterranean forests. Both post-fire management techniques should be instead adopted with caution in conifer forests.

The use of the Soil Conservation Service-curve number (SCS-CN) model for runoff predictions after rainstorms in fire-affected forests in the Mediterranean climate is quite scarce and limited to the watershed scale. To validate the applicability of this model in this environment, this study has evaluated the runoff prediction capacity of the SCS-CN model after storms at the plot scale in two pine forests of Central-Eastern Spain, affected by wildfire (with or without straw mulching) or prescribed fire and in unburned soils. The model performance has been compared to the predictions of linear regression equations between rainfall depth and runoff volume. The runoff volume was simulated with reliability by the linear regression only for the unburned soil (coefficient of Nash and Sutcliffe E = 0.73–0.89). Conversely, the SCS-CN model was more accurate for burned soils (E = 0.81–0.97), also when mulching was applied (E = 0.96). The performance of this model was very satisfactory in predicting the maximum runoff. Very low values of CNs and initial abstraction were required to predict the particular hydrology of the experimental areas. Moreover, the post-fire hydrological “window-of-disturbance” could be reproduced only by increasing the CN for the storms immediately after the wildfire. This study indicates that, in Mediterranean forests subject to the fire risk, the simple linear equations are feasible to predict runoff after low-intensity storms, while the SCS-CN model is advisable when runoff predictions are needed to control the flooding risk.

The use of check dams is a common strategy to reduce soil erosion in the Mediterranean headwaters. However, the effects of these control works on water flow rates and sediment yields have been scarcely investigated under possible scenarios of climate and land-use changes. On this regard, the use of hydrological models, such as SWAT, provide reliable hydrological predictions under variable environmental conditions. To fill this gap, this study has evaluated the effectiveness of check dams on the hydrological response of a forest headwater in Calabria (Southern Italy) in comparison with an unregulated subcatchment with very similar environmental conditions. In this regard, the effects of different combined scenarios of climate change (through three GCMs and two RCPs applied to a time period of the next 80 years) and land use (forest, pasture, and cropland) on water flow rates and sediment yields in the two headwaters were analysed using the SWAT model. The SWAT model was first calibrated in a third headwater with very similar climatic, soil, and land-use conditions, and this verification showed a satisfactory prediction capacity of water flow rate. The water flow rate prediction capacity of the model was satisfactory (coefficients of determination and efficiency of Nash and Sutcliffe equal to 0.71 and 0.67, respectively, and percent bias of 14.9%). No significant differences were detected for the water flow rates and sediment yields between the two subcatchments (with or without check dams) among the different land-use and climate change scenarios. This was linked to the low hydrological response of both headwaters to the forcing actions, which influenced the low effectiveness of the control works. SWAT estimated higher values of both mean and maximum values of water flow rates and sediment yields under RCP2.6 compared with RCP8.5. Both water flow rates and sediment yields were predicted to be very low under all climate and land-use scenarios. The regulated headwater with check dams was predicted to always produce more runoff and erosion compared with the subcatchment without check dams. The increases were predicted to be up to 60% for the maximum flow rate and 30–35% for the sediment yield in forest land use under RCP2.6. Although there was a limitation in this study due to the lack of validation of the erosion data (due to unavailable records of sediment yield), this study demonstrated how the use of check dams in headwater catchments may be not effective for soil conservation purposes several decades after their installation in Mediterranean semiarid areas, where the water flow and erosion rate are limited.

Several studies have analyzed the changes in individual soil properties and covers and quantified the hydrological response of burned forest soils (with or without post-fire treatment). Less research exists on the influence of these changes on runoff and erosion rates immediately after a prescribed fire and post-fire treatment. Moreover, hydrological modeling of burned areas is based on complex models rather than relying on simple regression equations. This study carries out a combined analysis of the hydrological response of soil and its driving factors in three forests (pine, oak, and chestnut) of Southern Italy that were subjected to prescribed fire and post-fire treatment with mulching. Moreover, simple regression models based on a limited set of soil properties/covers are proposed to predict runoff and erosion. The Principal Component Analysis has shown that the runoff coefficients increase when the water infiltration rate and litter cover decrease and repellency, ash cover, organic carbon content, and bare soil area increase. All the analyzed variables play a secondary role in influencing the sediment concentration. Due to these properties, clear differences in soil properties and covers have been found between unburned and burned soils. The distinctions between the burned soils (mulched or not) are much lower. The proposed regression models use a very low number of soil covers and two dummy variables as input parameters. These models are very accurate in simulating the surface runoff and soil erosion in all soil conditions in the short term.

The hydrological effects of straw mulching and salvage logging have been widely experimented in the Mediterranean forests affected by wildfires. In contrast, knowledge about the impacts of these post-fire management techniques on the physico-chemical properties of burned soils is poor, especially many years after the fire. In particular, no studies have evaluated the soil changes after the combinations of soil mulching and salvage logging after wildfires in Mediterranean forests. To fill this gap, this study explores the effects of straw mulching and salvage logging, applied individually or in combination to a burnt forest of Pinus halepensis Mill. of central-eastern Spain, on the physico-chemical properties of soil six years after a wildfire. Both the post-fire techniques significantly altered the organic matter, phosphorous, and carbonate contents of the burned soils as well as their C/N (carbon/nitrogen) ratio, while the texture and other chemical properties (pH, electrical conductivity, total nitrogen, potassium, cations/anions, and active limestone) of the soils were not significantly affected by these post-fire treatments. Organic matter (OM) and phosphorous (P) contents increased by 57% and 69%, respectively, in mulched soils in comparison to the burned but untreated plots. In logged soils, the OM increased by 27%, while P decreased by 17%. Salvage logging after straw mulching increased OM, albeit less than under the individual soil treatments (+13%), but noticeably reduced P (−39%). The C/N ratio practically underwent the same variation (+15–20%) after the combination of the two treatments. The principal component analysis and the agglomerative hierarchical cluster analysis applied to the soil properties measured in the plots under the individual and combined management show that the effects of salvage logging on soil properties appear to be more impactful compared to straw mulching.

Straw mulching and salvage logging are common management techniques after forest wildfires. However, these post-fire actions may result in an additional disturbance in burned soils, which may hamper the natural regeneration of forest species, especially in Mediterranean areas. The results of the investigations on the impacts of these post-fire management techniques are still insufficient, and especially about post-fire regeneration of Pinus halepensis Mill. This tree species is typical of the western Mediterranean Basin and is hardly threatened by forest wildfires. To fill these literature gaps, this study explores the effects of salvage logging after straw mulching on the regeneration of Pinus halepensis Mill. throughout four years after a wildfire. These effects have been also related to the changes in the main chemical properties of the supporting soils. Compared to the burned but non-treated areas, after four years of fire and post-fire treatments, we found that: (i) mulched and non-logged sites showed a significantly higher number of seedlings (+66%) with larger diameter (+12%) and higher height (+25%); (ii) logging did not significantly increase this number (+74%), but, in mulched and logged sites, the seedlings had significantly lower diameters (−18%) and heights (−9%); (iii) an increase in the seedling number (+29%), and decreases in the plant diameter (−34%) and height (−15%) were observed in the non-mulched and logged areas; (iv) no significant differences in the other morphometric parameters of seedlings were detected among all post-fire treatments; (v) a clear gradient between the organic matter content of soils and the number of plants growing under the four treatments was evident. These results support the task of forest managers in accelerating the recovery of natural vegetation in burned pine forests in the Mediterranean environment.