232
dropped drastically. The competitive potential of S. densiflora at higher elevations
was reflected in high above- and below-ground biomass and higher shoot densities, accompanied by elevated wrack accumulation and the absence of other
marsh plants. However, the alien invasion may be limited by the presence of the
autochthonous cordgrass at lower elevations (Castillo et al. 2008a). These results
were useful for restoration projects since they showed that healthy S. maritima
prairies would be an adequate way to limit the invasion of S. densiflora.
Finally, during all these above mentioned studies, we carried out pilot transplant experiments with S. maritima were carried out at different locations in the
Odiel Marshes, and variations on above- and below-ground biomass of S. maritima and on abiotic environment were subsequently analyzed along a chronosequence of six marshes created from 1997 to 2003, showing different sediment
dynamics, and adjacent natural marshes and unvegetated tidal flats. Results
showed that S. maritima behaves as an autogenic engineer, as its colonization of
bare sediments in created salt marshes yiels marsh level rise accompanied by
higher oxygenation and salinity. These modifications of the abiotic environment
were site-specific, depending mainly on sedimentary dynamics. At the same time,
abiotic environmental changes determined biomass production rates of S. maritima that were higher in more-accreting marshes; however, constant above-ground
biomass was kept from early in its development (2 years) (Castillo et al. 2008b).
These results pointed to the importance of the sedimentary dynamic when setting
realistic expectations for success criteria of created and restored wetlands. In
addition, we already knew that transplants of S. maritima will develop similar
above-ground biomass levels than natural populations within 2 years and that the
accumulation of below-ground biomass happens more slowly.
Once the methodology was tested at small-scale, a large restoration project was
carried out with four specific goals: (1) to recover native vegetation, restoring the
degraded landscape; (2) to phytostabilize oil-polluted sediments; (3) to prevent erosion and stabilize banks; and (4) to promote the conservation of S. maritima, an
endangered species included on some European red lists.
Plantation zones were delimited with small wood stakes between +1.50 and
+2.30 m SHZ (8.37 ha) based on the lower general distribution limit of S. maritima
in the tidal range (1.41 m SHZ) (Castillo et al. 2000). Planting was carried out at a
density of 1 clump per m
2
using a triangular-shaped herringbone planting method to
maximize sediment occupation. Halimione portulacoides clumps were planted at
the edges of interior marshes to accelerate its colonization and many S. maritima
clumps were accompanied by Sarcocornia perennis ssp. perennis since the extraction areas where natural populations where S. maritima was being outcompeted by
S. perennis (Figueroa et al. 2003).
The monitoring of this restoration project offered very interesting results to
remediate metal pollution in estuaries. Our results showed the success from the
point of view of vegetation of restoring European low salt marshes using S.
maritima and S. perennis plantations since they are able to reproduce, 2.5 year
after restoration, the typical plant zonation pattern (Curado et al. 2014b)
(Fig. 7.10). At the same time than vegetation development, erosion was lower in
S.M. Vallés et al.
dropped drastically. The competitive potential of S. densiflora at higher elevations
was reflected in high above- and below-ground biomass and higher shoot densities, accompanied by elevated wrack accumulation and the absence of other
marsh plants. However, the alien invasion may be limited by the presence of the
autochthonous cordgrass at lower elevations (Castillo et al. 2008a). These results
were useful for restoration projects since they showed that healthy S. maritima
prairies would be an adequate way to limit the invasion of S. densiflora.
Finally, during all these above mentioned studies, we carried out pilot transplant experiments with S. maritima were carried out at different locations in the
Odiel Marshes, and variations on above- and below-ground biomass of S. maritima and on abiotic environment were subsequently analyzed along a chronosequence of six marshes created from 1997 to 2003, showing different sediment
dynamics, and adjacent natural marshes and unvegetated tidal flats. Results
showed that S. maritima behaves as an autogenic engineer, as its colonization of
bare sediments in created salt marshes yiels marsh level rise accompanied by
higher oxygenation and salinity. These modifications of the abiotic environment
were site-specific, depending mainly on sedimentary dynamics. At the same time,
abiotic environmental changes determined biomass production rates of S. maritima that were higher in more-accreting marshes; however, constant above-ground
biomass was kept from early in its development (2 years) (Castillo et al. 2008b).
These results pointed to the importance of the sedimentary dynamic when setting
realistic expectations for success criteria of created and restored wetlands. In
addition, we already knew that transplants of S. maritima will develop similar
above-ground biomass levels than natural populations within 2 years and that the
accumulation of below-ground biomass happens more slowly.
Once the methodology was tested at small-scale, a large restoration project was
carried out with four specific goals: (1) to recover native vegetation, restoring the
degraded landscape; (2) to phytostabilize oil-polluted sediments; (3) to prevent erosion and stabilize banks; and (4) to promote the conservation of S. maritima, an
endangered species included on some European red lists.
Plantation zones were delimited with small wood stakes between +1.50 and
+2.30 m SHZ (8.37 ha) based on the lower general distribution limit of S. maritima
in the tidal range (1.41 m SHZ) (Castillo et al. 2000). Planting was carried out at a
density of 1 clump per m
2
using a triangular-shaped herringbone planting method to
maximize sediment occupation. Halimione portulacoides clumps were planted at
the edges of interior marshes to accelerate its colonization and many S. maritima
clumps were accompanied by Sarcocornia perennis ssp. perennis since the extraction areas where natural populations where S. maritima was being outcompeted by
S. perennis (Figueroa et al. 2003).
The monitoring of this restoration project offered very interesting results to
remediate metal pollution in estuaries. Our results showed the success from the
point of view of vegetation of restoring European low salt marshes using S.
maritima and S. perennis plantations since they are able to reproduce, 2.5 year
after restoration, the typical plant zonation pattern (Curado et al. 2014b)
(Fig. 7.10). At the same time than vegetation development, erosion was lower in
S.M. Vallés et al.