Water infiltration is a basic parameter to understand the hydrological response of semi-arid or arid soilswhere runoff generation is dominated by infiltration-excesssubjected to wildfire. To evaluate the hydrological effects of straw application on a sandy loam soil after wildfire, the unsaturated hydraulic conductivity, water content and temperature of mulched and nonmulched (considered as control) soils were monitored throughout eight months. Compared to untreated soils, straw maintained higher temperatures and water contents in mulched plots, but reduced their unsaturated hydraulic conductivity, particularly in the drier season. These results suggest that straw release may lead to a decrease of water infiltration capacity of soils subjected to wildfire, with particular evidence in summer in the case of heavy storm occurrence.

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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.

This study evaluates soil hydraulic conductivity (SHC) and water repellency (SWR) in three mixed forest stands in relation to site plant and soil characteristics. The studied forest stands were (i) Pinus nigra Arn. ssp salzmannii and Quercus ilex; (ii) P. nigra Arn. ssp salzmannii and Juniperus Thurifera; (iii) P. nigra Arn. ssp salzmannii, Q. ilex and Juniperus Thurifera. A 100‐ to 120‐year‐old unmanaged P. nigra Arn. ssp salzmannii stand was also chosen as control. The hydrological variables, physico‐chemical properties and surface characteristics of soils were surveyed. Soil water infiltration was higher in Pinus + Juniper mixed forest and Pinus + Quercus + Juniper mixed forests compared to unmanaged Pinus stands. None of the studied forest stands shows a high level of repellency. Only a slight repellency (in unmanaged stands dominated by pines) or moderate repellency (in soils with Pinus and Juniper) were evident, while soils with Pinus and Quercus were not repellent. Differences in SHC among the forest species were driven primarily by the soil texture and associated structure and secondarily by soil organic matter and associated SWR. The latter was mainly due to organic matter content of the soils, but others of the soil physico‐chemical properties and covers analysed were found as influencing parameters to discriminate SWR among mono‐specific and mixed forest stands. While SHC at the studied forest stands could be predicted using organic matter as well as sand and clay contents of the soil, SWR is the result of several hydrological and physico‐chemical parameters.

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 prescribed fire and mulching were dependent on the time elapsed from their application and forest species. In general, mulching was not effective in limiting the changes in the monitored soil properties compared to the pre-fire values. Each forest species showed different temporal trends in changes of soil properties.

Given the intrinsic hydrological cycle made of large input of water vapour and intense precipitation producing large volumes of water and sediment, modelling runoff and water losses in humid tropical watersheds is important for forest and water resources management. For instance, reliable simulations of the water cycle in such environments are a prerequisite for predictions of water quality, soil erosion and the climate change effects on water resources. The distributed parameter, physically based, continuous simulation, daily time step AnnAGNPS model, was implemented in almost completely forested (98% of its area, 0.56 km) Cunha watershed (Brazil) to assess its capability to simulate hydrological processes under tropical conditions. The simulated surface runoff was compared to 4-year observations with statistical indices on several time scales. The model, running with default CN of forest, showed poor predictions of runoff. After increasing CN from 63 to 72 by calibration, the runoff prediction capability of AnnAGNPS was satisfactory on annual, seasonal and monthly scales, while daily runoff predictions were less accurate. Modelling water losses at event scale showed that the effect of forest vegetation on water retention during a single precipitation was more limited than for longer periods (months, seasons and years), since evapo-transpiration and interception account for small shares (>20%) of total precipitation. This study demonstrated that the AnnAGNPS model has reliable runoff prediction capacity in tropical forest watersheds at the annual and seasonal scales (E > 0.73), whereas daily runoff simulations are less accurate (E = 0.44). The use of this model may prove an important tool for water resource and territory management in tropical rainforests.

Check dams are widely used for soil conservation at the watershed scale. When structurally sound, these engineering control works retain sediment as planned. However, there is limited information describing the influence of site characteristics on post-construction condition including structural stability and sediment retention capacity. More specifically, the effects of channel morphology, check dam geometry and vegetation characteristics as potentially influencing factors on sediment retention capacity at the watershed level are poorly understood. Thus, an investigation applying field and remotely sensed measurements, multi-regression models, redundancy and sensitivity analysis, and correlation analysis was conducted in a Mexican watershed where the characteristics of 273 check dams were evaluated 3-5 years after construction. Vegetation cover and dimensions of the channel were found to be the most important factors influencing check dam fate. Taller structures experienced the greatest failure risk, in contrast to lower and wider structures and associated vegetation cover that retained long and wide sediment wedges, which helped to stabilise the check dams. The potential sediment storage capacity of the check dams mainly depends on the downstream height of the structure, but also on the vegetation cover near the structure walls; check dams constructed across a range of channel dimensions are able to effectively store sediment. Overall, this study provides a quantitative evaluation of the dominant factors influencing the post-construction conditions of check dams and their ability to store sediment, and thus provides land managers insights into the best strategies for soil conservation at the watershed scale using check dams.