Environmental Engineering Reference
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sion (Vallejo et al . 2009). To ensure successful estab-
lishment, selection of woody species for restoration
should be based, as much as possible, on the natural
fl ora and vegetation of the area, and on the specifi c
biophysical characteristics of the site. Traditionally,
pine trees were planted in many areas in the Mediter-
ranean Basin for catchment protection and sand dune
stabilization. Pines commonly have high survival rates,
allowing a relatively quick revegetation success.
However, extensive pine plantations also provide an
excellent fuel bed for large, devastating fi res. Pine
woodlands also have low resistance and resilience
in the face of recurrent fi res, and Mediterranean pines
do not resprout after fi re. On the contrary, most native
hardwoods and, in general, woody sclerophyllous trees
and shrubs resprout (Paula et al . 2009 ). Therefore,
combining pines and hardwoods would take advantage
of the complementary features of both groups of
species, for example the high survival and fast growth
of pines and the high fi re resilience - that is, effi cient
resprouting capacity - of oaks (Pausas et al . 2004 ).
Early attempts to introduce broad-leaved resprouting
species in the Mediterranean Basin (e.g. Quercus spp.)
failed because of high seedling mortality and, even
until the late twentieth century, techniques for intro-
ducing these species in Mediterranean conditions were
poorly developed. Since the last few decades, the intro-
duction of hardwoods is becoming common in affores-
tation programmes, although the degree of success is
still variable. Recently, afforestation objectives are
widening their scope, so the diversity of introduced
species is increasing in MCRs. New programmes even
consider shrubland restoration, such as the restoration
and rehabilitation of mixed espinales in a central Chile
programme led by Carlos Ovalle of the Instituto
Nacional de Investigaciones Agropecuarias. That long-
standing programme is developing management and
intervention techniques useful in restoring the struc-
ture and former levels of diversity and productivity of
the mixed, anthropogenic Acacia caven formation
(Ovalle et al . 1999). Therefore, new species, never
tested before, including shrubs, are becoming of inter-
est for restoration.
The reintroduction of hardwoods and other native
woody species in degraded lands would require
improved restoration techniques, in order to increase
their degree of success. Drought is the critical factor
hindering seedling survival under Mediterranean con-
ditions. However, irrigation is seldom used in restora-
tion projects of southern European countries or indeed
Table 11.2 Mediterranean restoration techniques
concerned with water.
Objective
Technique
Increase water-use
effi ciency
Selection of drought-tolerant
species and ecotypes
Seedling preconditioning
Improve below-ground
performance
Improve nutritional status
Increase water
supply
Soil preparation and amendment
Irrigation
Microsite selection
Tree shelters
Mulching
Microsite selection
Control of competing species
Reduce water
losses
any of the MCRs. In central Chile, for example, where
summer drought is particularly long and severe, all
available water is reserved for other uses, mostly agri-
culture and tourism. In general, in the MCRs, as in all
semi-arid and arid regions, the implementation costs
of watering restoration sites in rugged and remote
areas are prohibitively high. Therefore, as irrigation is
not feasible, in most cases, improving rainfall capture
and water - use effi ciency become key factors for plant
survival and growth. Two common practices in this
regard are seedling manipulation and site preparation
practices (Table 11.2). As elsewhere, species assem-
blages and nursery and fi eld techniques must be tai-
lored to different landscapes and landscape units, and
restoration strategies should make use of available
resources and functional processes remaining in the
degraded site.
As most woody late-successional species do not form
a permanent seed bank (Huston & Smith 1987),
seeding woody species is an attractive technique to
reintroduce target species owing to its low cost, the low
impact of fi eld operations and the improved possibili-
ties for treating remote areas through aerial seeding.
However, high predation risk and uncertain seed ger-
mination and seedling establishment under dry condi-
tions are serious managerial constraints for the direct
use of seeding (Vallejo et al . 2009). From several pine-
seeding experiments carried out in Spain, right after
major fi res, only one produced acceptable seed germi-
nation rate and seedling survival, despite very favour-
able weather conditions (Pausas et al . 2004 ).
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