**5. Fire effects on soil water repellency: A laboratory approach with contrasted soils**

#### **5.1 Methods**

Water repellency is a soil property that affects its hydrological response and its erodibility (Cerdà & Doerr, 2008; Jordán et al., 2010). In this chapter, the effect of an experimental fire is studied on the soil water repellency of three different ecosystems. Three experimental soils have been selected in the NE of Spain with different properties (Table 3).

the greatest increase occurring in soil heated to 500°C. Soil aggregate stability (SAS) of both soils was reduced by heating to 250°C with greater reductions at 500°C, likely due to a reduction in organic matter and clay size particle content. Bulk density and particle density increased in both soils when heated to 500°C. Water availability (difference between field capacity and permanent wilting point) increased when soils were heated to the highest temperature, likely due to texture and structural modifications. The addition of ashes increased organic matter content, C/N ratio, and pH in both soils and increased nutrient availability, especially in the calcareous soil where soil addition was higher than

Soil respiration were quickly enhanced in calcareous soil but depleted in gypsiferous soil for intermediate heating treatments (150°C and 250°C). At the highest temperature (500°C), these biological properties were significantly reduced in both soil types and on a long term basis. Black ash addition increased basal respiration in both soils but did not affect other biological properties. These results demonstrate the existence of both labile and permanent effects of soil burning and a differential response to C dynamics as a function of soil

The unburned or control soils (25ºC) have originally contrasting properties (C versus G soil) that are not strongly altered at intermediate temperatures (150ºC, 250ºC). But the highest heat treatment (500ºC) conducted on both soils (C500 vs G500) showed a lot of similarities as

Fig. 7. Dendrogram of experimental calcareous (C) and gypsiferous (G) soils at different temperatures (25ºC, 150ºC, 250ºC, 500ºC) and ash addition (A). Numbers 0 to 25 shows the

Water repellency is a soil property that affects its hydrological response and its erodibility (Cerdà & Doerr, 2008; Jordán et al., 2010). In this chapter, the effect of an experimental fire is studied on the soil water repellency of three different ecosystems. Three experimental soils

**5. Fire effects on soil water repellency: A laboratory approach with** 

have been selected in the NE of Spain with different properties (Table 3).

rescaled distance cluster combine, and 1 to 10 are the case numbers.

in gypsiferous one.

**contrasted soils** 

**5.1 Methods** 

properties (Badía & Martí, 2003b).

result of the degradation of their initial properties (Fig. 7).


Table 3. Some characteristics of the studied soils and their ecosystems.

Non-altered blocks of soil have been obtained in the field in every area. All treatments have been carried out three times. Once in the laboratory, all the soil blocks have been air-dried and they have been burnt with a blowlamp (Llovet et al., 2008) up to reaching a maximum of 250ºC at 1 cm depth (Fig. 8).

Fig. 8. Soil blocks were burned with a blowlamp reaching 250ºC at 1 cm soil depth.

Soil Erosion and Conservations Measures in Semiarid Ecosystems Affected by Wildfires 99

translocation into the soil depth of lipid fractions released from burning organic matter or

Some rehabilitation practices have been implemented as urgent measures to control soil erosion in areas affected by wildfire in thesemiarid Central Ebro Valley (Figure 10): rehabilitation practices include herb seeding, re-mycorrhization and mulching with barley straw and pine woodchip. The effectiveness of these treatments are discussed in this

Fig. 10. Rural depopulation, land abandonment and afforestation with flammable species

In a paired plots design, treatments of seeding, seeding and mycorrhized, seeding and mulching, and control (untreated) erosion plots were established in four different slopes and

Fig. 11. Left: detail of seeding and mulching plots under slow and poor conditions of postfire cover regeneration. Right: planting oak species on hillslopes which have been removed

on calcareous one (*Calcaric Regosols*) and gypsiferous (*Haplic Gipsisols*) soils (Fig. 11).

increased wildifres in Mediterranean semiarid ecosystems: Burned Aleppo pine afforestation in Fraga mountains (left) and abandoned terraces in Sarsa Castle (right).

**6. Rehabilitation practices in areas affected by wildfires** 

biomass (González et al., 2004).

section.

**6.1 Methods** 

because of high fire frequency.

In order to evaluate the soil water repellency, the water drop penetration time (WDPT) test has been used, applying three drops per soil block. In addition, the water repellency variation is assessed in three different levels of depth (at the surface, at 2 cm and 5 cmdepth). The water repellency classification criterion is the one used by Doerr et al., 2009).
