Alteration of topography and the consequent change in the hydroperiod are two
of the main causes of wetland degradation in the site (Flores-Verdugo et al. 2007).
By compiling the site history use during the last 40 years and the consequences of
the land use in terms of the topography and the hydrology of the area, it is possible
to understand the invasion patterns of an African grass that had been introduced to
neighboring ranches. In the study area, available water was not a limiting factor.
Yetter’s (2004) findings showed that water flowed all year, mainly as a subsuperficial flow, and that the direction was from the sugarcane fields and the dune
lake, through the dune slack, toward the mangrove and lagoon (Fig. 16.1). This
same author obtained the hydrographs for the site prior to the beginning of restoration activities.
16.2.2 Restoration Activities
Restoration activities in the dune slack were focused on increasing the flooding
level and reducing the cover of E. pyramidalis (hereafter named Echinochloa).
In the dry season, in areas dominated by Echinochloa, the grass layer was cut at
ground level using a machete. In areas where Echinochloa was present but mixed
with native vegetation, there was selective cutting and extraction of native plants
to be relocated. As vegetation was cleared, patches dominated by Dalbergia
brownei (hereafter named Dalbergia) were found on the eastern border. This is a
native shrub that grows as a climbing shrub on isolated trees, covering large areas,
creating shaded microhabitats, and replacing wetland plant species. The areas
covered by Dalbergia were also cut at ground level. Where Echinochloa or
Dalbergia re-sprouted, herbicide was sprayed locally. When the herbicide application was not enough to eliminate the sprouts, prescribed burning or covering
with black plastic for 2–3 months were necessary. The sprouts of Dalbergia that
still resisted were injected with herbicide on the basal portion of the sprouting
branches (Fig. 16.2; Table 16.1).
At the beginning of the rainy season in 2007, the drain pipe leading to the
mangroves was blocked and the wetland flooded for 16 months, ensuring that the
grass stems, which had been cut, were drowned. The areas that were flooded but had
a low proportion of Echinochloa in relation to desirable native species were covered
with shade cloth to reduce the amount of light by 50 %, at a height of approximately
2 m above ground level. Every 2 months, teams of three or four people manually
removed the re-sprouts of Echinochloa. After 16 months of permanent flooding, we
unblocked the drain pipe to allow the flow of water into the mangrove. In elevated
areas where flooding was shallow, the ground level was lowered around 30–40 cm
with a shovel to ensure higher levels of flooding (Fig. 16.2).
16 Interdune Wetland Restoration
259
of the main causes of wetland degradation in the site (Flores-Verdugo et al. 2007).
By compiling the site history use during the last 40 years and the consequences of
the land use in terms of the topography and the hydrology of the area, it is possible
to understand the invasion patterns of an African grass that had been introduced to
neighboring ranches. In the study area, available water was not a limiting factor.
Yetter’s (2004) findings showed that water flowed all year, mainly as a subsuperficial flow, and that the direction was from the sugarcane fields and the dune
lake, through the dune slack, toward the mangrove and lagoon (Fig. 16.1). This
same author obtained the hydrographs for the site prior to the beginning of restoration activities.
16.2.2 Restoration Activities
Restoration activities in the dune slack were focused on increasing the flooding
level and reducing the cover of E. pyramidalis (hereafter named Echinochloa).
In the dry season, in areas dominated by Echinochloa, the grass layer was cut at
ground level using a machete. In areas where Echinochloa was present but mixed
with native vegetation, there was selective cutting and extraction of native plants
to be relocated. As vegetation was cleared, patches dominated by Dalbergia
brownei (hereafter named Dalbergia) were found on the eastern border. This is a
native shrub that grows as a climbing shrub on isolated trees, covering large areas,
creating shaded microhabitats, and replacing wetland plant species. The areas
covered by Dalbergia were also cut at ground level. Where Echinochloa or
Dalbergia re-sprouted, herbicide was sprayed locally. When the herbicide application was not enough to eliminate the sprouts, prescribed burning or covering
with black plastic for 2–3 months were necessary. The sprouts of Dalbergia that
still resisted were injected with herbicide on the basal portion of the sprouting
branches (Fig. 16.2; Table 16.1).
At the beginning of the rainy season in 2007, the drain pipe leading to the
mangroves was blocked and the wetland flooded for 16 months, ensuring that the
grass stems, which had been cut, were drowned. The areas that were flooded but had
a low proportion of Echinochloa in relation to desirable native species were covered
with shade cloth to reduce the amount of light by 50 %, at a height of approximately
2 m above ground level. Every 2 months, teams of three or four people manually
removed the re-sprouts of Echinochloa. After 16 months of permanent flooding, we
unblocked the drain pipe to allow the flow of water into the mangrove. In elevated
areas where flooding was shallow, the ground level was lowered around 30–40 cm
with a shovel to ensure higher levels of flooding (Fig. 16.2).
16 Interdune Wetland Restoration
259