The wettability of ash from burned vegetation and its relationship to Mediterranean plant species type, burn severity and total organic carbon content
Abstract Immediately following a wildfire, a layer of ash and charred material typically covers the ground. This layer will gradually be reduced, being redistributed by rainfall, wind or animals, by partial dissolution and by incorporation into the soil. Ash can increase or decrease the post-fire runoff and erosion response, depending upon the soil and ash properties and the ash thickness. One aspect of ash that has remained unknown and which may affect the variability in the hydrological response of the burned soil is its wettability. This study examines the wettability of ash using the Water Drop Penetration Time (WDPT) test, its relationship with total organic carbon (TOC) content and co…
Hydrological effects of a layer of vegetation ash on underlying wettable and water repellent soil
Abstract Hydrological processes after a wildfire may take place under soil conditions altered by heat and by the presence of ash. Soil and ash interact as a two-layer system with poorly understood hydrological properties, especially when ash covers water repellent soil. Here we quantify the effect of an ash layer (0, 5, 15 and 30 mm depth) covering wettable and water repellent soil on (i) the hydrological response and the mechanism of runoff generation and (ii) the water repellency dynamics, for a rainfall event followed by different drying periods and a second rainfall event. Laboratory rainfall simulation experiments (82.5 mm h − 1 during 40 min) at small plot-scale (0.09 m 2 ) were perfo…
The effect of ash and needle cover on surface runoff and erosion in the immediate post-fire period
Abstract Hillslopes are thought to be most susceptible to enhanced surface runoff and erosion immediately following wildfire due to removal of protective vegetation and litter cover, and in many cases a fire-induced reduction in soil wettability. This enhanced susceptibility declines as vegetation and litter layer recover. For logistical reasons, however, few studies have been able to examine the responses of burnt terrain immediately following burning and little is therefore known about the effect of the wettable ash layer that often covers the ground until it is redistributed or removed by wind or water erosion. Here we quantify the effects of ash and needle cast ground cover on surface r…
Organic matter and wettability characteristics of wildfire ash from Mediterranean conifer forests
Abstract Thermogravimetric analysis (TGA) and water repellency (wettability) determination of ash samples collected following wildfires at four different Mediterranean conifer forest sites in eastern Spain were conducted to provide insights into variations in key chemical and physical characteristics of ash. TGA allowed the evaluation of organic matter (OM) and inorganic carbonate (IC) characteristics and their role in ash wettability. Thermogravimetric profiles were recorded for 40 ash samples (ten from each site). The persistence of water repellency of all ash samples was assessed by the Water Drop Penetration Time (WDPT) test. OM contents decreased, whilst OM stability indices and IC con…
Repelencia al agua en suelos forestales afectados por incendios y en suelos agrícolas bajo distintos manejos y abandono
Soil water repellency determines the water available in the soil system, the runoff generation and the geomorphologic processes. This study examines the soil wettability during the summer of 2008 and 2009 in forest soils with different fire history, and in agricultural soils with different managements. Water repellency was assessed using the Water Drop Penetration Time test (WDPT). Results indicate that water repellency is more frequent and persistent in forest soils than in agricultural ones. In the former, water repellency is reduced a year after a fire and is not recovered during at least 12 years. In agricultural soils, it is found under no till treatment, whereas sites treated with her…
Influence of vegetation recovery on soil hydrology and erodibility following fire: an 11-year investigation
The present study investigates long-term changes in soil hydrological properties and erodibility during the regrowth of different types and densities of vegetation following a severe wildfire in the Serra Grossa Range, eastern Spain. Twelve plots of similar slope and soil characteristics, naturally recolonized by four different plant species (trees, herbs, shrubs and dwarf shrubs) were examined using rainfall simulations during an 11-year period. The mean erosion rate was 80 g m−2 h−1, 6 months after the fire under wet-winter conditions, declining to 30 g m−2 h−1 in the following summer and reaching <10 g m−2 h−1 after 2 years. Considerable variation under the different vegetation types …
The effect of ant mounds on overland flow and soil erodibility following a wildfire in eastern Spain
This study examines the soil hydrological and erosional effects of ant mounds during summer and winter conditions following a wildfire in scrub terrain in eastern Spain. Forty rainfall simulations (1 m2 plots, 1 h duration, 78 mm h−1 intensity) were carried out over plots with mounds (n = 20) and mound-free control plots (n = 20) in August 2002, and repeated in December. By winter, some of the mound material had been removed and some vegetation regrowth occurred. Overall, mound presence increased soil erodibility in summer and winter due to the availability of highly erodible mound material. However, mound plots showed higher mean overland flow rates in summer (10·1 vs 6·9% for control plot…
FT-IR spectroscopy reveals that ash water repellency is highly dependent on ash chemical composition
Abstract After a fire, an ash layer is commonly present, which influences soil properties and hillslope hydrology. The wettability of ash, which can vary from highly absorbent to water repellent, is an important characteristic in this context. Recent work has suggested that ash wettability is related to its degree of combustion, which in turn, can be expected to determine ash chemical composition. In this paper we therefore examine the relationship between ash water repellency and ash chemical composition. Ten ash samples with different wettability were each taken from four burned Mediterranean forest sites located at Albaida (A), Lliber (L), Navalon (N), and Pinoso (P), in the east of Spai…
Current Wildland Fire Patterns and Challenges in Europe: A Synthesis of National Perspectives
Changes in climate, land use, and land management impact the occurrence and severity of wildland fires in many parts of the world. This is particularly evident in Europe, where ongoing changes in land use have strongly modified fire patterns over the last decades. Although satellite data by the European Forest Fire Information System provide large-scale wildland fire statistics across European countries, there is still a crucial need to collect and summarize in-depth local analysis and understanding of the wildland fire condition and associated challenges across Europe. This article aims to provide a general overview of the current wildland fire patterns and challenges as perceived by natio…
Corrigendum to “Wildland fire ash: Production, composition and eco-hydro-geomorphic effects”, Earth Sci. Rev. 130 (2014) [103–127]
Corrigendum to “Wildland fire ash: Production, composition and eco-hydro-geomorphic effects”, Earth Sci. Rev. 130 (2014) [103–127] Merche B. Bodi⁎, Deborah A. Martin, Victoria N. Balfour, Cristina Santin, Stefan H. Doerr, Paulo Pereira, Artemi Cerda, Jorge Mataix-Solera a ECOBE (Ecosystem Management Research Group), Department of Biology, University of Antwerp, Belgium b SEDER (Soil Erosion and Degradation Research Group), Departamento de Geografia, Universitat de Valencia, Valencia, Spain c National Research Program, U.S. Geological Survey, Boulder, CO, USA d Department of Ecosystem and Conservation Sciences, College of Forestry and Conservation, University of Montana, Missoula, USA e Depa…
Influence of Initial Water Content on the Wettability of Autoclaved Soils
Autoclaving is a commonly used practice to destroy microbial activity in soils but is thought to have a limited effect on other soil properties. Small changes in chemical composition have been reported, but there have been no previous reports of any alteration of physical properties. This study, however, showed that autoclaving can cause a major change in soil hydraulic properties. For samples with intermediate water contents (10-35% v/v), it caused severe or extreme water repellency in three of four soil types tested, although no effect for initially low or high water contents was found. These findings have important implications for any experimental work involving soil autoclaving as a pr…
Soil wettability, runoff and erodibility of major dry-Mediterranean land use types on calcareous soils
This study examines six land uses (pine woodland, long unburnt scrubland, recently burnt scrubland, orange grove, olive grove and cereal crop), typical for calcareous soils in a dry-Mediterranean region such as eastern Spain, with regard to soil surface water repellency occurrence, hydrological response and erodibility. For each land use, we performed water drop penetration time (WDPT) tests and rainfall simulations respectively on in situ soils at ten replicate plots for extremely dry antecedent conditions in summer 2002 and for wet winter conditions, in early 2003 in the Canyoles river valley. In contrasts to what might have been expected, water repellency was absent or subcritical (WDPT …
Wildland fire ash: Production, composition and eco-hydro-geomorphic effects
Abstract: Fire transforms fuels (i.e. biomass, necromass, soil organic matter) into materials with different chemical and physical properties. One of these materials is ash, which is the particulate residue remaining or deposited on the ground that consists of mineral materials and charred organic components. The quantity and characteristics of ash produced during a wildland fire depend mainly on (1) the total burned fuel (i.e. fuel load), (2) fuel type and (3) its combustion completeness. For a given fuel load and type, a higher combustion completeness will reduce the ash organic carbon content, increasing the relative mineral content, and hence reducing total mass of ash produced. The hom…
Spatial and temporal variations of water repellency and probability of its occurrence in calcareous Mediterranean rangeland soils affected by fires
Abstract Water repellency (WR) is a common soil property in many fire-affected ecosystems, but it also occurs in long-unburned terrain. It can vary in space at different scales (between point and pedon or slope and catchment) and time (during the same day, between seasons or years, or with a post-fire recovery period). This paper: i) reports on the occurrence and persistence of WR in fire-affected calcareous forest soils under Mediterranean climatic conditions, examining its spatial variability at macro-, meso- and micro-scales, and monthly changes with soil moisture content; and ii) develops exploratory models to estimate the probability of the natural background (not fire-induced) WR to o…