Forest fire effects on soil chemical and physicochemical properties, infiltration, runoff, and erosion in a semiarid Mediterranean region Assaf Inbar a,b , Marcos Lado c , Marcelo Sternberg d , Haim Tenau a , Meni Ben-Hur a, ⁎ a Institute of Soil, Water and Environmental Sciences, the Volcani Center, ARO, P.O. Box 6, Bet-Dagan 50250, Israel b Porter School of Environmental Studies, Tel-Aviv University, Ramat Aviv 69978, Israel c Area of Soil Science, Faculty of Sciences, University of A Coruna, A Zapateira s/n, 15071 A Coruna, Spain d Department of Molecular Biology and Ecology of Plants, The George S. Wise Faculty of Life Sciences, Tel-Aviv University, Ramat Aviv 69978, Israel abstract article info Article history: Received 21 July 2013 Received in revised form 14 January 2014 Accepted 17 January 2014 Available online xxxx Keywords: Wildfire Soil properties Infiltration Soil erosion Aggregate stability Forest fires are a major environmental concern, especially in the semiarid Mediterranean regions, where the long dry and hot summers and mild winters favor outbreaks of wildfires. The objective of this work was to study the effects of different fire treatments on physical, chemical, and physicochemical properties of Pale rendzina, and their impact on infiltration rate (IR), runoff and soil loss under consecutive rainstorms. After a wildfire in a forest located in northern Israel, soil samples were taken from an area that was directly exposed to fire (direct fire treat- ment) and from adjacent unburned (unburned soil treatment). Part of the unburned soil was heated in a muffle at 300 °C (heated soil treatment). Runoff, soil loss and IR values were measured for the various samples using a laboratory rainfall simulator, and aggregate stability was determined using slaking and dispersion values. The or- ganic matter, clay, and sand content, and cation exchange capacity were significantly lower in the heated soil than in the unburned soil. The CaCO 3 content in the heated soil was significantly higher than in the unburned and direct fire soils. In general, the IR values were highest, intermediate, and lowest and the runoff and soil loss amounts were lowest, intermediate, and highest in the heated, direct fire, and unburned soils, respectively. However, these differences decreased with progression of the consecutive rainstorms. Heating the soil to 300 °C enhanced soil-structure stability, most likely due to increased dehydration of 2:1 clay minerals and transforma- tion of iron and aluminum oxides which acted as cementing agents. In addition, soil heating increased the elec- trical conductivity (EC) and decreased the sodium adsorption ratio in the heated soil solution in the first rainstorm. These processes limited clay dispersion and seal formation in the heated soil, leading to high IR values and low runoff and soil loss. In the second and third rainstorms, EC of the soil solution decreased, which in turn increased clay dispersion. This lessened the differences in the IR values and runoff and soil loss amounts between the fire treatments in these rainstorms compared to the first rainstorm. © 2014 Published by Elsevier B.V. 1. Introduction Semiarid Mediterranean regions are characterized by long, dry and hot summers and short, wet, mild winters (Hötzl, 2008). These condi- tions are favorable for wildfires and indeed, there has been an increase in the number of wildfires and total burnt area in the Mediterranean re- gion since the 1960s (Kliot, 1996; Pausas and Vallejo, 1999; Wittenberg and Malkinson, 2009). The rise in the number of wildfires is ascribed mainly to the accumulation of combustible fuels in abandoned areas (Pausas and Fernández-Muñoz, 2012; Shakesby, 2011), afforestation of mono-specific flammable tree species (Shakesby, 2011), and climate change (Pausas, 2004; Pausas and Fernández-Muñoz, 2012). Possible harmful effects of forest fire include total or partial loss of vegetation and litter cover in the forest (e.g., Ben-Hur et al., 2011; Shakesby, 2011; Soto et al., 1997), increases in surface runoff, soil erosion, and downstream flooding (Ben-Hur et al., 2011; Wagenbrenner et al., 2006), and export of sediments, organic matter, nutrients, and pollut- ants that can endanger downstream aquatic and flood-zone habitats and associated human infrastructures (Ferreira et al., 2008; Shakesby and Doerr, 2006). Reduction of infiltration rates (IRs) and an increase in surface runoff and soil erosion following forest fires have been widely reported (e.g., Benavides-Solorio and MacDonald, 2001, 2005; Inbar et al., 1997, 1998; Martin and Moody, 2001; Mayor et al., 2007; Moody and Martin, 2001; Shakesby, 2011; Wittenberg and Inbar, 2009). The increase in runoff and soil erosion has been attributed mainly to: (i) increasing soil water repellency that can decrease the IR (DeBano, 2000; DeBano et al., 1998; Letey, 2001; Neary et al., 1999); (ii) a decrease in transpira- tion as a result of vegetation losses in the forest which, in turn, alters the soil–water relationships (Ben-Hur et al., 2011); (iii) amplification of soil proofing by transport and accumulation of ash particles (Cerdà and Doerr, 2008; Etiégni and Campbell, 1991; Larsen et al., 2009; Mallik Geoderma xxx (2014) xxx–xxx ⁎ Corresponding author at: Institute of Soil, Water and Environmental Sciences, ARO, Volcani Center, P.O. Box 6 Bet-Dagan, Israel, 50-250. Tel.: +972 39683634. E-mail address: meni@volcani.agri.gov.il (M. Ben-Hur). GEODER-11571; No of Pages 8 0016-7061/$ – see front matter © 2014 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.geoderma.2014.01.015 Contents lists available at ScienceDirect Geoderma journal homepage: www.elsevier.com/locate/geoderma Please cite this article as: Inbar, A., et al., Forest fire effects on soil chemical and physicochemical properties, infiltration, runoff, and erosion in a semiarid Mediterranean..., Geoderma (2014), http://dx.doi.org/10.1016/j.geoderma.2014.01.015