Mediterranean forests are frequently subject to wildfires, inducing risks of high runoff and loss of nutrient-rich topsoil. The mechanisms influencing these post-fire effects are spatially variable due to differences in vegetation density, litter composition, soil texture and structure, and fire intensity, and therefore difficult to separate. The characteristics of the soil surface in the immediate post-fire period are of critical importance to the hydrological response and erosion susceptibility of the burnt hillslope and catchment. In laboratory experiments, uniform soil, controlled temperature and rain regimes were used to create a controlled environment to isolate the impact of certain influencing parameters. In this study, for a Rendzina soil, we investigated the post-fire impacts of laboratory fire and two successive rainfall (rotating disktype) simulation experiments to evaluate short-term effects of fire on soil hydrological and erodibility parameters by examining (i) soil water repellency (WR) levels and distribution, (ii) surface cover features, and (iii) infiltration, runoff and erosion responses to simulated rain on control (bare and pineneedle covered) and burnt (with and without ash cover) samples. Fire-induced surface WR tested in the laboratory by grid-wise Water Drop Penetration Time tests (WDPT), revealed moderate WR, which decreased for all treatments after rainfall. The response to rain (33 mm h-1) differed for the two simulation runs. The rates of drainage and runoff of the burnt samples in the first run varied between the values of cover (low runoff, high infiltration) and bare (high runoff, low infiltration). Drainage in the ash-covered samples was twice as high as ashremoved samples. In the second run, both samples showed a similar response compared to bare conditions. These laboratory observations suggest that WR and protection by ash are factors to consider in assessing the erosion susceptibility of a burnt forest soil. Furthermore, possible management implications based upon this research are that: 1) ash can have several important roles immediately after a forest fire by protecting the forest soil from rain splash erosion, and with its high water holding capacity, absorbs rainfall, thereby reducing runoff; and 2) ash has no negative influence upon soil infiltration demonstrating the important benefits of ensuring the longer term maintenance of post-fire ash within the burnt landscape. Finally, management actions including mulching further enhance soil stability and minimize soil erosion.
Bibliographical notePublisher Copyright:
© Universidad de La Rioja.
- Mediterranean soils
- Post-fire management
- Water repellency
ASJC Scopus subject areas
- Geography, Planning and Development
- Environmental Science (miscellaneous)
- Earth and Planetary Sciences (miscellaneous)