activities as drainage for agriculture, aquaculture, and pasturelands, floodplain reclamation, construction of flood control structures, excavation of peat for fuel and the
modification and straightening of river channels (Bobbink et al. 2006).
Wetlands can be found in a great variety of geomorphological settings along
floodplains, and in low areas or depressions in almost every environment. Dune
slacks in temperate and tropical regions are usually formed in depressions and can
harbor wetlands that remain flooded only during 2 or 3 months of the year (humid and
wet slacks) or permanently, forming dune lakes. These important types of wetlands
are also facing degradation and destruction because of expanding agriculture and
population growth. Considering this scenario, restoration has been a priority.
Wetland restoration aims to restore lost biodiversity or provide services, such as
flood-peak reduction and water quality improvement (Zedler 2000). Since the early
1970s, the science for successful wetland restoration has been developed and
although we have made much progress on that front, the diversity of wetland types
and their individual characteristics requires restoration remedies that are customized
to particular situations (Erwin 2009). In general, the success of wetland restoration
may depend on several factors, such as the presence of seed banks (Kelly et al. 2009),
the hydrological regime (Bruland et al. 2003), the microtopography (Kurt et al.
2009), the forms and amounts of nutrients in the soil (Christopher et al. 2008), the
habitat and matrix type (Roe et al. 2003), the landscape setting (Simenstad et al.
2006), disturbance regimes, and invasive species (Lyubov et al. 2009; Miller and
Zedler 2003). Nevertheless, several authors agree that the effectiveness of the wetland restoration will depend mainly on the flow of the water through the system and
the degree to which re-flooding occurs. Restoration of wetland structure, increased
secondary productivity, and enhanced wildlife value can be achieved by subtle
improvements in hydrology in former wetlands that have been converted to uplands,
such as pasture (David 1999).
Hydrology is a primary filter for the recruitment of vegetation and propagule bank
expression in herbaceous wetlands (Battaglia and Collins 2006; Flores-Verdugo
et al. 2007). Germination of some species is inhibited by inundation (Kozlowski
2002), whereas others require it (Leck and Simpson 1995). Some studies have
analyzed the differential responses of native and exotic plants to hydrological
conditions in order to explain the dominance of some species over others (Miller and
Zedler 2003; López Rosas 2007). The re-flooding of former agricultural areas is a
relatively common strategy of wetland restoration. Ideally, under flooded conditions
undesired species may present a combination of lower germination and physiological stress from flooding on seedlings that can lead to lower plant densities with
increasing water depth. On the other hand, floating-leaved and submerged aquatics
had higher cover; vegetation converged on simpler, less variable communities
dominated by obligate wetland species. One gap in our understanding is the strength
of the linkage between hydroperiod and vegetation expression and the thresholds in
the changes in hydrology that affect vegetation composition or species abundances.
256
H. López-Rosas et al.
modification and straightening of river channels (Bobbink et al. 2006).
Wetlands can be found in a great variety of geomorphological settings along
floodplains, and in low areas or depressions in almost every environment. Dune
slacks in temperate and tropical regions are usually formed in depressions and can
harbor wetlands that remain flooded only during 2 or 3 months of the year (humid and
wet slacks) or permanently, forming dune lakes. These important types of wetlands
are also facing degradation and destruction because of expanding agriculture and
population growth. Considering this scenario, restoration has been a priority.
Wetland restoration aims to restore lost biodiversity or provide services, such as
flood-peak reduction and water quality improvement (Zedler 2000). Since the early
1970s, the science for successful wetland restoration has been developed and
although we have made much progress on that front, the diversity of wetland types
and their individual characteristics requires restoration remedies that are customized
to particular situations (Erwin 2009). In general, the success of wetland restoration
may depend on several factors, such as the presence of seed banks (Kelly et al. 2009),
the hydrological regime (Bruland et al. 2003), the microtopography (Kurt et al.
2009), the forms and amounts of nutrients in the soil (Christopher et al. 2008), the
habitat and matrix type (Roe et al. 2003), the landscape setting (Simenstad et al.
2006), disturbance regimes, and invasive species (Lyubov et al. 2009; Miller and
Zedler 2003). Nevertheless, several authors agree that the effectiveness of the wetland restoration will depend mainly on the flow of the water through the system and
the degree to which re-flooding occurs. Restoration of wetland structure, increased
secondary productivity, and enhanced wildlife value can be achieved by subtle
improvements in hydrology in former wetlands that have been converted to uplands,
such as pasture (David 1999).
Hydrology is a primary filter for the recruitment of vegetation and propagule bank
expression in herbaceous wetlands (Battaglia and Collins 2006; Flores-Verdugo
et al. 2007). Germination of some species is inhibited by inundation (Kozlowski
2002), whereas others require it (Leck and Simpson 1995). Some studies have
analyzed the differential responses of native and exotic plants to hydrological
conditions in order to explain the dominance of some species over others (Miller and
Zedler 2003; López Rosas 2007). The re-flooding of former agricultural areas is a
relatively common strategy of wetland restoration. Ideally, under flooded conditions
undesired species may present a combination of lower germination and physiological stress from flooding on seedlings that can lead to lower plant densities with
increasing water depth. On the other hand, floating-leaved and submerged aquatics
had higher cover; vegetation converged on simpler, less variable communities
dominated by obligate wetland species. One gap in our understanding is the strength
of the linkage between hydroperiod and vegetation expression and the thresholds in
the changes in hydrology that affect vegetation composition or species abundances.
256
H. López-Rosas et al.