**6.1 Methods**

98 Soil Erosion Studies

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).

Fire affect soil water repellency in a different way according to soil type and soil depth (Table 4). Fire decreased significantly the presence of water repellency on the surface of all experimental soils: Phaeozems, Calcisols and Cambisols. The fire reduced water repellency even in depth in Phaeozems (to 5 cm depth) and Calcisols (to 2 cm depth). Unlike, fire increased water repellency in Cambisols at 5 cm depth, from hydrophilic (unburned soil

**Soil Group Soil depth (cm) Unburned Soil Burned Soil** *P*  Phaeozem 0 833.6656.0 0.690.14 0.003 2 1100.6479.3 12.8022.0 <0.001 5 835.3438.6 13.011.3 <0.001 Calcisol 0 666.0333.2 8.020.2 0.001 2 382.2412.9 16.639.9 0.029 5 79.087.4 40.067.4 0.305 Cambisol 0 14.26.9 0.810.1 <0.001 2 1.40.9 107.9207.3 0.162 5 3.71.3 273.9293.7 0.025 Table 4. Effect of fire on water repellency (WDPT, s) of Phaeozems, Calcisols and Cambisols

Effect of fire on water repellency of a **Calcisol**

012345

Waxes and similar lipid materials could be mostly responsible for the original soil water repellency, which can be enhanced or reduced according to soil properties (Fig. 9). The increase in water-repellent conditions at 5 cm depth in Cambisol could be attributed to the

Control Burned 0

2

Soil depth (cm)

5

Effect of fire on water repellency of a **Cambisol**

012345

Control Burned

WDPT Class

WDPT Class

**5.2 Results and discussion** 

Fire effect on water repellency of a **Phaeozem**

012345

WDPT class

0

2

Soil depth (cm)

5

samples) to strongly hydrophobic (burned soil samples).

at different soil depths (mean values and standard deviation; n=9).

0

2

Soil depth (cm)

5

Fig. 9. Fire effect on water repellency (WDPT classes) in the studied soils.

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

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 because of high fire frequency.

Soil Erosion and Conservations Measures in Semiarid Ecosystems Affected by Wildfires 101

**Treatments C S SM SMS C S SM SMS Mg ha-1 year-1** 3,63a 1,24c 1,21c 1,11cd 1,78b 0,97cd 0,98cd 0,67d **Control / treatment** - 2,9 3,0 3,3 - 1,8 1,8 2,7 Table 5. Average erosion rate (n=4) in Gerlach collectors under different soil treatments: burned control plots (C), seeded plots (S), seeded and mycorrhized plots (SM), and seeded and mulched with straw (SMS). The plots were monitorized during two years after wildfire in Fraga hillslopes (NE-Spain). Different letters between treatments and soils indicates

The parallel contour seeeding treatment increases soil cover and acts as a sucessive microbarriers to the maximal slope to reduce flow velocity and runnoff coefficient while increasing infiltration and trapping sediments. This was verified in experiments with rainfall simulator (Badía et al., 2008). The runoff coefficient was significantly lower for seeding plots (13 to 38%) than for control soils (45 and 58% for calcareous and gypsiferous soils respectively). The lower calcareous soils runoff is associated with better physical and chemical properties than gypsiferous soils, differences in soil characteristics which are also reflected in the vegetation cover (Fig. 9). Because of the heterogeneity of rainfall in the region, the erosion is generated in the most rainy months of the study on both the gypsiferous and calcareous soils, and then is when there are significant differences between seeding and control plots. The Figure 13 note these differences on gypsiferous burned soils,

Fig. 13. Sediment yield (g m-2) under different treatments (control and seeding) on gypsiferous burned soils (n=4) and monthly rainfall (mm) along the period of study. Asterisks indicate the significant differences between seeding and control plots in the

Cumulative soil loss was higher in gypsiferous soils than in calcareous soils for control plots (untreated). Although the application of any of the treatments reduced these rates and the

significant differences (LSD test, P<0,05).

and is representative also for calcareous soils.

reporting month. From Badía & Martí, 2000.

**Gypsiferous Soil Calcareous Soil** 

All sites were north-facing with a slope of around 20º. The seeding treatment consisted of the addiction of legumes and grass seed mixture, either native or established through cultivation in the region: *Medicago sativa* L.*, Medicago truncatula* Gaertn.*, Onobrychis viciifolia* Scop.*, Vicia villosa* Roth*, Agropyron cristatum* (L.) Gaertn.*, Dactylis glomerata* L.*, Lolium rigidum* Gaud. and *Phalaris canariensis* (L.). Planting was done manually in rows, perpendicularly to the maximal slope (parallel contour seeding). The sowing rate for the whole mixture was 30 g m-2, with an equivalent weight for each species. Mulching consisted of barley (*Hordeum vulgare* L.) straw covering the soil surface at a 100 g m-2 rate (Badía & Martí, 2000). And mycorrhization has consisted of contribution of vesicular-arbuscular mycorrhizae (*Glomus mossae*) to increase the nutrient and water potential of sown plants (Mataix et al., 2007; Vallejo, 1996).

## **6.2 Results and discussion**

Plant cover (native and sown plants) in both soils (calcareaous and gypsiferous) after four months of seeding treatments are shown (Fig. 12).

Fig. 12. Soil cover (%) in seeded plots (S) and seeded+mycorrhized plots (MS) on calcareous (C) and gypsiferous (G) soils after four months of treatments application.

Native plant coverage in calcareous soils (40%) is greater than in gypsiferous soils (10%) where physical, chemical and biological properties are relatively worse. Moreover, in calcareous soils the resprouters are higher than in gypsiferous one. In gypsiferous plots the principal native species was *Helianthemum syriacum* while *Brachypodium retusum* was dominant in calcareous plots, in some cases reaching 50% of total plant cover.

It is important to remark that plant cover of seeded plants is similar in both soils (~30%). Among the introduced species *Lolium rigidum* covered about 12% of soil surface. The other seeded species had a similar importance, 5% of the total for *Onobrychis vicifolia* and about 2- 4% for each of the other six species.

Regarding the effectiveness of applied measures on soil erosion, we found differences between soils because bare soil after treatments was about 45% in gypsiferous soils and only 15% in calcareous one (Fig. 9). The soil loss in gypsiferous soils twice that one in calcareous soils (Table 4). The cumulative annual erosion rate measured in Gerlach boxes was about 4 Mg ha-1 year-1 for gypsiferous soils, 3 times more than treated soil. And in calcareous soils, soil losses was about 2 Mg ha-1 year in control plots were about 2 times higher than treated plots (Table 5).

All sites were north-facing with a slope of around 20º. The seeding treatment consisted of the addiction of legumes and grass seed mixture, either native or established through cultivation in the region: *Medicago sativa* L.*, Medicago truncatula* Gaertn.*, Onobrychis viciifolia* Scop.*, Vicia villosa* Roth*, Agropyron cristatum* (L.) Gaertn.*, Dactylis glomerata* L.*, Lolium rigidum* Gaud. and *Phalaris canariensis* (L.). Planting was done manually in rows, perpendicularly to the maximal slope (parallel contour seeding). The sowing rate for the whole mixture was 30 g m-2, with an equivalent weight for each species. Mulching consisted of barley (*Hordeum vulgare* L.) straw covering the soil surface at a 100 g m-2 rate (Badía & Martí, 2000). And mycorrhization has consisted of contribution of vesicular-arbuscular mycorrhizae (*Glomus mossae*) to increase the

Plant cover (native and sown plants) in both soils (calcareaous and gypsiferous) after four

Fig. 12. Soil cover (%) in seeded plots (S) and seeded+mycorrhized plots (MS) on calcareous

Native plant coverage in calcareous soils (40%) is greater than in gypsiferous soils (10%) where physical, chemical and biological properties are relatively worse. Moreover, in calcareous soils the resprouters are higher than in gypsiferous one. In gypsiferous plots the principal native species was *Helianthemum syriacum* while *Brachypodium retusum* was

It is important to remark that plant cover of seeded plants is similar in both soils (~30%). Among the introduced species *Lolium rigidum* covered about 12% of soil surface. The other seeded species had a similar importance, 5% of the total for *Onobrychis vicifolia* and about 2-

Regarding the effectiveness of applied measures on soil erosion, we found differences between soils because bare soil after treatments was about 45% in gypsiferous soils and only 15% in calcareous one (Fig. 9). The soil loss in gypsiferous soils twice that one in calcareous soils (Table 4). The cumulative annual erosion rate measured in Gerlach boxes was about 4 Mg ha-1 year-1 for gypsiferous soils, 3 times more than treated soil. And in calcareous soils, soil losses was about 2 Mg ha-1 year in control plots were about 2 times higher than treated

(C) and gypsiferous (G) soils after four months of treatments application.

dominant in calcareous plots, in some cases reaching 50% of total plant cover.

nutrient and water potential of sown plants (Mataix et al., 2007; Vallejo, 1996).

**6.2 Results and discussion** 

4% for each of the other six species.

plots (Table 5).

months of seeding treatments are shown (Fig. 12).


Table 5. Average erosion rate (n=4) in Gerlach collectors under different soil treatments: burned control plots (C), seeded plots (S), seeded and mycorrhized plots (SM), and seeded and mulched with straw (SMS). The plots were monitorized during two years after wildfire in Fraga hillslopes (NE-Spain). Different letters between treatments and soils indicates significant differences (LSD test, P<0,05).

The parallel contour seeeding treatment increases soil cover and acts as a sucessive microbarriers to the maximal slope to reduce flow velocity and runnoff coefficient while increasing infiltration and trapping sediments. This was verified in experiments with rainfall simulator (Badía et al., 2008). The runoff coefficient was significantly lower for seeding plots (13 to 38%) than for control soils (45 and 58% for calcareous and gypsiferous soils respectively). The lower calcareous soils runoff is associated with better physical and chemical properties than gypsiferous soils, differences in soil characteristics which are also reflected in the vegetation cover (Fig. 9). Because of the heterogeneity of rainfall in the region, the erosion is generated in the most rainy months of the study on both the gypsiferous and calcareous soils, and then is when there are significant differences between seeding and control plots. The Figure 13 note these differences on gypsiferous burned soils, and is representative also for calcareous soils.

Fig. 13. Sediment yield (g m-2) under different treatments (control and seeding) on gypsiferous burned soils (n=4) and monthly rainfall (mm) along the period of study. Asterisks indicate the significant differences between seeding and control plots in the reporting month. From Badía & Martí, 2000.

Cumulative soil loss was higher in gypsiferous soils than in calcareous soils for control plots (untreated). Although the application of any of the treatments reduced these rates and the

Soil Erosion and Conservations Measures in Semiarid Ecosystems Affected by Wildfires 103

**/Rainfall Years Author** 

391 mm 10 Badía et al., 2007

200 mm 6 Oliet et al., 2000

400 mm <sup>1</sup>Carrera et al.,

Málaga, 400 mm <sup>1</sup>Navarro et al.,

Agost, 301 mm <sup>4</sup>Baeza et al., 1991a

277 mm <sup>6</sup>Cortina et al.,

414 mm 40 Olarieta et al.,

350 mm 0,4 Martí and Badía,

277 mm 1 Maestre and

400 mm 1 Alloza and

500 mm 1 www.creaf.uab.es

420 mm 28-46 www.creaf.uab.es

1000 mm 1 Espelta et al.,

391 mm 10 Badía et al., 2007

Málaga, 400 mm <sup>1</sup>Navarro et al.,

400 mm 1 Carrera et al.,

Agost, 301 mm 4 Baeza et al., 1991a

1-3 Peñuelas et al., 1997

1997

1997

and 1991b

2004

2000

1995

Cortina, 2004

Vallejo, 1999

/iefc

/iefc

1993

1997

1997

and 1991b

<sup>1</sup>Ducry and Toth, 1992

<sup>1</sup>Viñuales and Badía, 1995

Alloza, Teruel

Paracuellos del Jarama, 430 mm

Aspe, 306 mm;

Alicante,

Murallot de Fraga, 345 mm

Sant Simó, Fraga

Garraf

Almatret

Alloza, Teruel

Aspe, 306 mm;

Puechbon (Francia), 807 mm

**Species Survival and/or growth Location** 

S: 94,5% (90,7-97,5). HGR=35,8cm/year (30,7-42,3). DGR=9,7mm/year(8,7-11,6)

*P. halepensis* S < 50% Almería,

HGR: 15-52 cm/year

*P. halepensis* S: 13-56 % Sierra Estancias

*P. halepensis* S: 60 % Montes de

HGR: 11, 8 to 18,5 cm/year

DGR: 1,6-2,4 mm/year

S:88%(S)100%(N).HGR:14,7cm/yea r(S)-23,2(N).DGR: 1,9(S) to 3.3mm/year(N)

*P. halepensis* HGR: 0,85 -2,73 cm/year Castillonroy,

DGR=3,8-4,8 mm/year

*P. halepensis* S: 80% Alicante

*P. halepensis* S: 68-71% Valencia

DGR: 0,29-0,37 cm/year

DGR: 1,52-2,59 cm/year

S: 40,7%(27,5-64,2%).HGR=7,5 cm/year (4,8-11,3%). DGR=2,0 mm/year(1,0-2,1)

*P. halepensis* S: 8-59% Montseny

*Q. ilex* S: < 40 % Montes de

HGR:2,4 cm/year - 1,3 cm/year

*Q. ilex* S: 2-51 % Sierra Estancias

*P. halepensis* S (1-2-3 years): 56-43-36%

*P. halepensis* S: 20-48 %. HGR: 6,1-9,4 cm/year.

*P. halepensis* HGR=4,1-6,5 cm/year

*P. halepensis* HGR: 8,9-11.2 cm/year

*P. halepensis* HGR: 17,7-26,1 cm/year

*Q. ilex* S: 35-49%.

*Q. ilex* DGR: 1.05 mm/year

*P. halepensis* S: 73-95%

*P. halepensis* 

*P. halepensis* 

*Q. ilex* 

benefits are clearly apparent, the erosion levels of post-fire degradation with no treatment cannot be classified as severe. These facts are consistent with other studies where wildfires are considered as a perturbation with a relatively severe temporary impact (Cerdá & Doerr, 2005). Analyzing the vegetal cover from the point of view of the pastoral value (Badía et al., 1994), fresh and dry plant matter increased with sowing as well as non-nitrogenous products. Straw mulching is the most effective treatment against soil erosion, inducing some improvement both in quantity and quality of plant matter in both types of soils. Remycorrhization did not affect these parameters. Endomycorrhizae recovery after the fire has been rapid (Table 4), hence the low response of a mycorrhizal inoculum allochthonous (Badía & Martí, 1994a and 1994b).

Although at intermediate temperatures soil microbial activity is quickly enhanced, for specific organisms, such as endomycorrhizal fungi, linked to the recovery of vegetation, this recovery is slower (Table 6).


Table 6. Characterization of endomycorrhizal state (x sd) in burned soils (n=4) one year after wildfire in NE-Spain (Barceló et al., 1994).

#### **6.3 Other treatment: planting of shrubs and trees**

In this case the treatment was applied only on young soils developed on calcareous marls (*Xeric Torriorthent*) in Fraga (Fig. 14). Five plant species were transplanted in man-made holes: two woody species (*Pinus halepensis, Quercus ilex*) and three shrub species (*Juniperus phoenicea, Pistacia lentiscus, Retama sphaerocarpa*); all of them ectomycorrhizae and with only one sap. After a year of monitoring, the portentaje of survival is almost null for *Quercus ilex* while for the other species is between 94 and 100%. Height growth rate is significantly different between the five species (average of the different slopes in which were transplanted): *Pinus halepensis* (16,4±5,8 mm/year), *Pistacia lentiscus* (10,3±3,9 mm/year), *Retama sphaerocarpa* (5,0±1,6 mm/year), *Juniperus phoenicea* (2,5±1,1 mm/year) and *Quercus ilex* (0,5±0,4 mm/year). In a similar way, diameter growth rate maintains the following order: *Pinus halepensis* (2,3±0,08 mm/year), *Retama sphaerocarpa* (1,4±0,09 mm/year), *Pistacia lentiscus* (1,1±0,06 mm/year), *Juniperus phoenicea,* (0,04±0,03 mm/year) and *Quercus ilex* (0,03±0,02 mm/year). These latter species show a relative diameter growth rate not statistically differentiated (0,4-0,6 mm mm-1 year-1), whereas the relative height growth rate follows the order: *Pinus halepensis* and *Pistacia lentiscus* (0,5 mm mm-1 year-1), *Retama sphaerocarpa* (0,4 mm mm-1 year-1), *Juniperus phoenicea* (0,25 mm mm-1 year-1). All the species studied show a clear sensitivity to soil water content, showing growth increments in spring and autumn, as well as greater increments in north slopes than in the southern slopes (Viñuales & Badía, 1995).

Table 7 summarizes the growth parameters (survival, height growth rate and diameter growth rate) of the species mentioned, used for reforestation in areas degraded by fire and other disturbances, and studied for different authors.

benefits are clearly apparent, the erosion levels of post-fire degradation with no treatment cannot be classified as severe. These facts are consistent with other studies where wildfires are considered as a perturbation with a relatively severe temporary impact (Cerdá & Doerr, 2005). Analyzing the vegetal cover from the point of view of the pastoral value (Badía et al., 1994), fresh and dry plant matter increased with sowing as well as non-nitrogenous products. Straw mulching is the most effective treatment against soil erosion, inducing some improvement both in quantity and quality of plant matter in both types of soils. Remycorrhization did not affect these parameters. Endomycorrhizae recovery after the fire has been rapid (Table 4), hence the low response of a mycorrhizal inoculum allochthonous

Although at intermediate temperatures soil microbial activity is quickly enhanced, for specific organisms, such as endomycorrhizal fungi, linked to the recovery of vegetation, this

**soil** 50.016.9 33.6014.3 48.222.1 37.811.8 **Diversity index** 1.2660.19 0.9800.12 1.5860.2 1.0250.35

Table 6. Characterization of endomycorrhizal state (x sd) in burned soils (n=4) one year

In this case the treatment was applied only on young soils developed on calcareous marls (*Xeric Torriorthent*) in Fraga (Fig. 14). Five plant species were transplanted in man-made holes: two woody species (*Pinus halepensis, Quercus ilex*) and three shrub species (*Juniperus phoenicea, Pistacia lentiscus, Retama sphaerocarpa*); all of them ectomycorrhizae and with only one sap. After a year of monitoring, the portentaje of survival is almost null for *Quercus ilex* while for the other species is between 94 and 100%. Height growth rate is significantly different between the five species (average of the different slopes in which were transplanted): *Pinus halepensis* (16,4±5,8 mm/year), *Pistacia lentiscus* (10,3±3,9 mm/year), *Retama sphaerocarpa* (5,0±1,6 mm/year), *Juniperus phoenicea* (2,5±1,1 mm/year) and *Quercus ilex* (0,5±0,4 mm/year). In a similar way, diameter growth rate maintains the following order: *Pinus halepensis* (2,3±0,08 mm/year), *Retama sphaerocarpa* (1,4±0,09 mm/year), *Pistacia lentiscus* (1,1±0,06 mm/year), *Juniperus phoenicea,* (0,04±0,03 mm/year) and *Quercus ilex* (0,03±0,02 mm/year). These latter species show a relative diameter growth rate not statistically differentiated (0,4-0,6 mm mm-1 year-1), whereas the relative height growth rate follows the order: *Pinus halepensis* and *Pistacia lentiscus* (0,5 mm mm-1 year-1), *Retama sphaerocarpa* (0,4 mm mm-1 year-1), *Juniperus phoenicea* (0,25 mm mm-1 year-1). All the species studied show a clear sensitivity to soil water content, showing growth increments in spring and autumn, as well as greater increments in north slopes than in the southern slopes

Table 7 summarizes the growth parameters (survival, height growth rate and diameter growth rate) of the species mentioned, used for reforestation in areas degraded by fire and

**Gypsiferous Soil (G) Calcareous Soil (C) Control Burned Control Burned** 

(Badía & Martí, 1994a and 1994b).

after wildfire in NE-Spain (Barceló et al., 1994).

**6.3 Other treatment: planting of shrubs and trees** 

other disturbances, and studied for different authors.

recovery is slower (Table 6).

**Nº spores /g dry** 

(Viñuales & Badía, 1995).


Soil Erosion and Conservations Measures in Semiarid Ecosystems Affected by Wildfires 105

In a parallel experience the two woody species, *Pinus halepensis* and *Quercus ilex*, were planted in man-made holes too, in gypsiferous and calcareous soils affected by wildfire. After almost three years, *P. halepensis* survival is high, 81,2% on gypsiferous soils and 41,7% on calcareous soils. The *Q*. *rotundifolia* just had a 17,1% in gypsiferous and 8,3%on calcareous soils (Martí & Badía, 1995). The low survival in calcareous soils (more fertile than gypsiferous soils), is due to competition with other species, especially with *Brachypodium ramosum* with which it has been important. In fact, the mortality of *Pinus halepensis* is inversely related to vegetal recovery,

 Mortality, % = 2,054 (Vegetation cover, %) – 23,513 r2 = 0,578; P<0,01 (2) More evidence of the role of soil water as a limiting factor in the study area, is that when reforestation practices are accompanied by a support irrigation in the plantation phase of the species, the survival rate and growth rises significantly. This was observed in a study of reforestation of opencast surfaces in the Val of Ariño coalfield (Teruel, NE-Spain) (Badía et al., 2007). In this study, the effect of a slope gradient on the growth and survival of different species 10 years after the reconstruction of mining banks was evaluated. Their survival shows significant differences: 95% *Pinus halepensis*, 81% *Pistacia lentiscus*, 62% *Juniperus phoenicea*, 41% *Quercus ilex* and 34%*Quercus coccifera*. Aleppo pine has been the fastest growing both height (36 cm year-1) and basal diameter (10 mm year-1), because of its greater adaptation in semiarid environments. For the other species, height values are less than 12 cm year-1 and 2,1 mm year-1 for basal diameter values. Growth and survival obtained here were higher than those of the same species in other afforestations in semiarid conditions. This outcome demonstrates the adequacy of species and applied techniques of restoration, in particular irrigation of summer season support, that allow a long-term reliability of

In the semi-arid environments of NE-Spain, there are different types of soil conditioned by the lithology of the substrate derived, and whose erosion reponse is significantly divergent. Thus the calcareous burned soils with low stoniness and loamy clay texture, as well as eroded gypsiferous soils, show runoff and erosion levels higher than gypsiferous soils, and especially that colluvial soils. The coverage provided by vegetation is a key element to stop sheet erosion on these soils. The combined effect of heat and ash incorporation involves a number of changes in physical, chemical and biological characteristics of soils affected by wildfire. These effects vary according to intensity of the fire, the amount of ash incorporated and soil characteristics starting. The protective measures such seeding and mulching treatments involve a significant reduction of sediment yield in the first years after fire, higher in eroded gypsiferous soils than in fertile calcareous ones. The remycorrhization is not effective when the

In the forest domain of the area there is a diversity of species whose response after the fire is clearly different. Those with resprouting shrub species tend to recover its previous status faster, the vegetal recovery is higher and temporarily stable. In mature Aleppo's pine forest, the germination of pine is high; the pine density is 3-times higher before than after fire, although it will be prgressively reduced. The shrub and woody species introduced show a differential response according to the soil in which they are implanted and restoration

soil mycorrhizal status has already been recovered from the effects of fire.

techniques, especially related to soil water conditions.

which highlights the competition for soil water reserves:

reclaimed mine slopes.

**7. Conclusions** 


Table 7. Survival and growth of woody species used in restoration of areas affected by fires and other disturbances. Abbreviatures: S. Survival; HGR. Height growth rate; DGR. Diameter growth rate.

In a parallel experience the two woody species, *Pinus halepensis* and *Quercus ilex*, were planted in man-made holes too, in gypsiferous and calcareous soils affected by wildfire. After almost three years, *P. halepensis* survival is high, 81,2% on gypsiferous soils and 41,7% on calcareous soils. The *Q*. *rotundifolia* just had a 17,1% in gypsiferous and 8,3%on calcareous soils (Martí & Badía, 1995). The low survival in calcareous soils (more fertile than gypsiferous soils), is due to competition with other species, especially with *Brachypodium ramosum* with which it has been important. In fact, the mortality of *Pinus halepensis* is inversely related to vegetal recovery, which highlights the competition for soil water reserves:

$$\text{Mortality}, \; \%= 2.054 \text{ (Vegetation cover, \%)} - 23.513 \text{ r}^2 = 0.578; \text{P} \le 0.01 \tag{2}$$

More evidence of the role of soil water as a limiting factor in the study area, is that when reforestation practices are accompanied by a support irrigation in the plantation phase of the species, the survival rate and growth rises significantly. This was observed in a study of reforestation of opencast surfaces in the Val of Ariño coalfield (Teruel, NE-Spain) (Badía et al., 2007). In this study, the effect of a slope gradient on the growth and survival of different species 10 years after the reconstruction of mining banks was evaluated. Their survival shows significant differences: 95% *Pinus halepensis*, 81% *Pistacia lentiscus*, 62% *Juniperus phoenicea*, 41% *Quercus ilex* and 34%*Quercus coccifera*. Aleppo pine has been the fastest growing both height (36 cm year-1) and basal diameter (10 mm year-1), because of its greater adaptation in semiarid environments. For the other species, height values are less than 12 cm year-1 and 2,1 mm year-1 for basal diameter values. Growth and survival obtained here were higher than those of the same species in other afforestations in semiarid conditions. This outcome demonstrates the adequacy of species and applied techniques of restoration, in particular irrigation of summer season support, that allow a long-term reliability of reclaimed mine slopes.
