Environmental Engineering Reference
In-Depth Information
rates, most Mediterranean tree seedlings growing
inside tree shelters gradually acclimatize to adverse
climatic conditions outside the shelter and improve
shoot growth. When this does not happen, unbalanced
growth in stem height may occur, and the plant
becomes highly susceptible to wind damage.
Costs and b enefi ts of ecotechnological
i nvestments
Between 1992 and 2010, CEAM Foundation and
University of Alicante (Spain) established 217 experi-
mental plantations on degraded semi-arid and dry sub-
humid areas. Initially, plantations used prevailing
technology at that time, that is, using a few species
(mostly pines and a small number of holm oaks), and
simple nursery cultivation techniques and basic soil
preparation. Over the past decade, plantations have
incorporated innovations in species selection, nursery
production, soil preparation and tending (e.g. mulches,
tree shelters, organic amendments etc.), according to
the discussion in previous sections. Seedling survival
after the fi rst summer in the fi eld (a major indicator of
plantation success) was strongly dependent on the
number of consecutive days with no signifi cant rainfall
(precipitation events <5 mm) in both old and new
plantations (Figure 11.5). But the slope of the relation-
ship between survival and drought length decreased
as advanced technologies were implemented. Under
severe drought, survival rate would double, and the
risk of total failure would decrease signifi cantly by
using advanced ecotechnology. One obvious interpre-
tation of these results is that plantations carried out on
harsh sites would require higher technological inputs
and investments to achieve a given target than those
on less harsh sites.
Figure 11.3
Survival and growth of Aleppo pine (
Pinus
halepensis
, circle) and holm oak (
Quercus ilex
, square)
seedlings in planting holes with (white) and without (black)
water-harvesting microcatchments during the fi rst year
after outplanting. Field experimental data on degraded
forests in the Region of Valencia (Spain). Different uppercase
or lowercase letters within each species mean signifi cant
differences in survival between treatments (P < 0.05). For
height growth, differences are indicated with *. (Modifi ed
from Fuentes
et al
. 2004 .)
Bird - m ediated r estoration
The role of plant-animal mutualisms has been sug-
gested for cost-effi cient restoration plans (Handel
1997). Bird-mediated restoration is based on the obser-
vation of succession of abandoned woody crops, such
as olive groves, carob groves, almond groves and vine-
yards. In these contexts, natural succession is signifi -
cantly faster than in nonwoody crop fi elds thanks to
the role of the trees as perch sites for frugivorous birds.
These birds discharge seeds of late-successional species
that germinate around the perching tree forming
a nucleus of intermediate or advanced succession
average stem size (Bellot
et al
. 2002 ; Figure 11.4 ).
Nevertheless, the use of this technique alone does not
guarantee plantation success. The root-shoot ratio of
protected seedlings is often lower inside tree shelters
than in unprotected seedlings, and this reduces the
capacity of seedlings to withstand prolonged drought.
Tree shelters signifi cantly increase seedling growth in
height with, however, the risk of producing elongated,
'leggy' stems. However, thanks to their slow growth
