Individual study: A comparison of Riley encased methodology and traditional techniques for planting and establishment of red mangroves Rhizophora mangle along the Indian River Lagoon, Florida, USA
Salgado Kent C.P. (1999) A comparison of Riley encased methodology and traditional techniques for planting red mangroves (Rhizophora mangle). Mangroves and Salt Marshes, 3, 215-225
Riley encased methodology (REM) i.e. encasement in full-length PVC tubes, appears the only method successful along coasts with high wave energy to restore degraded manngroves. As REM had only been recently developed, it was decided to further evaluate its effectiveness. The effectiveness of encasement in PVC tubes (half and full-length) and bamboo for planting red mangrove Rhizophora mangle in moderate to high wave energy environments was tested in the Indian River Lagoon on the east coast of Florida (USA).
The three encasement types tested were:
i) Full-length PVC pipe inside diameter 3.8 cm (REM) i.e. part of pipe sunk into sediment and part exposed, thus protecting root and shoot;
ii) Half length PVC pipe - only extending into the sediment with shoot exposed, thus reducing the amount of pipe needed whilst still stabilizing the root system;
iii) Full-length bamboo pipe - bamboo is available in many subtropical and tropical regions where the cost of PVC pipes might be inhibitive - also biodegradable (thus removal after mangrove establishment not required); outside diameter of c.9 cm, hollowed using a drill to an internal cavity of 3.8 cm diameter.
Mangroves were also planted conventionally - i.e. directly into the substrate with no encasement.
Each pipe had a vertical slit along the length to allow for water exchange and mangrove growth. The pipes were driven into the sediment until stable substrate was reached (c.50 cm at the selected sites).
Planting: Rhizophora propagules were collected and tested for viability and health before planting out. Planting was conducted in August and November 1997 at two sites each in Sebastian Inlet (27º50'10â€ N, 80º26'10â€) and Rocky Point (27º59'30â€N, 80º33'27â€). In August, at each of the Sebastian sites 35 propagules were assigned to each of the four treatments. At the Rocky Point sites, 35 propagules were assigned to the conventional, full-length and half-length PVC pipe treatments, but only13 were assigned to the bamboo pipe treatment due to difficulties inserting them into the sediment. In Novemebr, only conventional and full-length PVC pipe treatments were applied.
Propagules were planted 25 cm apart.
Monitoring: Survival, stem growth and number of leaves per plant was recorded twice a month for 8 months (August plantings) and 4 months (November plantings). Parameters indicative of wave energy were recorded: sediment grain size distribution (via soil core samples) in August 1997 and April 1998; and wave activity measured fortnightly.
Survival: Rhizophora planted within full-length PVC pipes had by far the highest survival and growth due to the protection they afforded from waves and currents. Propagules within bamboo seemed to fail due to insufficient light. Little difference was observed in survival between August and November plantings.
August planting - At Sebastian after 8 months, full-length PVC encasement had 87% survival, within bamboo 1.5%, and mangroves planted within half-length PVC pipes and conventionally both 0%. At Rocky Point, those within full-length PVC pipes had 76% survival, those in the other three treatments all died.
November planting - Survival at Sebastian after 4 months was 94% for full-length PVC encased mangroves and 0% for those conventionally planted. At Rocky Point survival was 100% in full-length pipes and 6% for those conventionally planted.
Growth: Significantly greater growth was observed at Sebastian than at the Rocky Point for the November plantings, but not for those planted in August. However, overall there was a significantly greater growth in mangroves planted in August.
Other than a significantly greater width of surf zone at Sebastian than at Rocky Point, there was no significant difference in the environmental parameters recorded between locations.
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