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Consistent with our field observations, the complete encasement of red mangrove seedlings has resulted in dramatic changes in the rate of development. The demonstrated ability of the encasement to stimulate and accelerate growth has contributed to the high survival vis-à-vis conventional planting methods. I believe this phenomenon is a result of several factors; however, most influential is phototropism, i.e. response to light as an orienting stimulus. Other factors appearing to contribute to this accelerated growth rate are identified in the methodology section. By planting in compliance with our specifications for seedling orientation, elevation, and encasement length, the propagule is induced to grow toward the primary light source at the top of the encasement. It should be noted that the prescribed thin-wall PVC is translucent and offers the plant adequate low intensity light to promote initial development.

In order to remove site specific factors as a variable influencing growth, we fabricated a test-bed for isolating specifically on the effects of phototropism. All seedlings were harvested from the same tree to lessen any potential genetic advantage that might be inherited from different donors. The propagules were then paired by size so that each seedling planted using encased method had a corresponding mate of the same initial size planted conventionally.

The adjacent photograph captures the test-bed at the end of 30 days, with encasements removed. The encased specimens budded earlier and had greater leaf development than those conventionally planted. The subsequent photograph was taken on the 75th day after planting. Those that were encased clearly show greater growth and leaf development. The table at the bottom documents the growth in inches/centimeters and the leaf count for each seedling. Although this is a relatively small sample, it is consistent with field observations and substantiates that phototropism contributes to the accelerated growth that has been associated with fully encased seedlings.





75TH DAY MEASUREMENTS
Encasement
Row 1
growth in/cm
Encasement
Row 1
# leaves
Encasement
Row 2
growth in/cm
Encasement
Row 2
# leaves
Conventional
Row 1
growth in/cm
Conventional
Row 1
# leaves
Conventional
Row 2
growth in/cm
Conventional
Row 2
# leaves
5.9 / 15.0
4
7.2 / 18.5
6
2.7 / 7.0
4
4.7 / 12.0
4
7.2 / 18.5
6
9.6 / 24.5
6
4.7 / 12.0
6
4.7 / 12.0
4
7.0 / 18.0
6
6.2 / 16.0
6
4.1 / 10.5
4
4.9 / 12.5
6
9.0 / 23.0
6
6.0 / 15.5
6
3.9 / 10.0
4
5.5 / 14.0
6
7.5 / 19.5
6
7.0 / 18.0
6
3.5 / 9.0
2
4.7 / 12.0
2


Copyright © 1996-1998. Robert W. Riley Jr. All rights reserved.

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Mangroves offer significant and unique habitat to birds, mammals, crustacea, and fish populations through a complex marine food chain, creation of breeding habitat, and establishment of restrictive areas that offer protection for maturing offspring. In addition, mangroves contribute to improved water quality by filtering and assimilating pollutants, stabilizing bottom sediments, and protecting shorelines from erosion."> Inadequacies in conventional red mangrove replenishment methods are primarily a result of their sensitivity to water depth, tidal action, and wave activity. A major problem in successful planting is the difficulty in finding suitable locations with adequate and appropriate environmental conditions favorable to the rooting and sustenance of the mangrove during its early stages of development. To have any potential of establishing thriving mangroves when using conventional methods, the seedlings must be planted only in areas adequately shielded from any substantial wave action or upland run-off. These conditions translate into restrictions not simply on the geographic location of a potential replenishment project, but also on the relative size and range of any replanting. Many areas that would be desirable for mangrove planting present formidable factors that prohibit the successful introduction of the tree.

The necessity of implementing mangrove replenishment projects is supported by the documented reduction in mangrove trees throughout Florida's estuary systems. Increases in population, water-front development, agriculture, boating and related activities have resulted in significant increases in the types and quantities of pollutants reaching intracoastal and coastal waters. Additionally these factors have contributed to a significant decline in mangrove habitat necessary to maintain commercial and recreational fisheries. Therefore, the importance of mangroves to a healthy marine ecology has dramatically increased. As natural members of estuary systems, mangroves mitigate the environmentally adverse and destructive effects of development and consequential pollution. In an effort to promote mangrove replenishment on a wide geographic basis an alternative planting method, called "Encased Replanting", has been developed. This new planting method is not subject to the limitations of conventional techniques.

Encased Replanting applies new methodology and technique in mangrove restoration. With employment of the Encased method, mangroves can be established in areas with significant tidal action, wave activity, and upland run-off. Mangroves offer a logical contribution to coast line protection, estuary restoration and a healthy marine environment. The Encased method effectively enables the establishment of mangrove trees where conventional planting techniques can not succeed. Mangrove trees are an indigenous species to Florida and a major contributor to the state's marine environment. The mangrove tree is a halophyte, a plant that thrives in salty conditions. It has the ability to grow where no other tree can, thereby making significant contributions that benefit the environment. Their coverage of coastal shorelines and wetlands provides many diverse species of birds, mammals, crustacea, and fish a unique, irreplaceable habitat. Mangroves preserve water quality and reduce pollution by filtering suspended material and assimilating dissolved nutrients. The tree is the foundation in a complex marine food chain and the detrital food cycle. The detrital food cycle was discovered by two biologists from the University of Miami, Eric Heald & William Odum, in 1969. As mangrove leaves drop into tidal waters they are colonized within a few hours by marine fungi and bacteria that convert difficult to digest carbon compounds into nitrogen rich detritus material. The resulting pieces covered with microorganisms become food for the smallest animals such as worms, snails, shrimp, mollusks, mussels, barnacles, clams, oysters, and the larger commercially important striped mullet. These detritus eaters are food for carnivores including crabs and fish, subsequently birds and game fish follow the food chain, culminating with man. Many of these species, whose continued existence depends on thriving mangroves, are endangered or threatened. It has been estimated that 75% of the game fish and 90% of the commercial species in south Florida rely on the mangrove system. The value of red mangrove prop root habitat for a variety of fishes and invertebrates has been quantitatively documented. Data suggest that the prop root environment may be equally or more important to juveniles than are sea grass beds, on a comparable area basis. Discovery of the importance of mangroves in the marine food chain dramatically changed the respective governmental regulation of coastal land use and development. In order to overcome the deficiencies in existing replanting techniques, Encased Replanting was developed as a more productive and adaptable alternative to current techniques. The method focuses on isolating the seedling into a controlled environment at the actual replanting site. The encasement artificially creates an environment favorable to the seedling's initial development while protecting the plant long enough to become well established. The isolation physically separates the seedling from surrounding conditions that are unfavorable to early development of the tree. By segregating the seedling from harsh environmental factors the encasement provides protection for the seedling during its formative stages and continues through the first three years of growth. By the third year the young red mangrove starts to sprout its aerial roots which will physically secure the plant to the bottom and ensure its long term survival. The development of aerial roots is a crucial step that ensures viability of the developing tree. The aerial roots provide for the exchange of gases needed for respiration and will enable the tree to root even in mud lacking oxygen. Once aerial roots extend into the bottom they will provide adequate protection from displacement and ensure the continuing subsistence of the plant. Aerial or prop roots are a distinctive root structure of the Red Mangrove and a characteristic that makes the Encased method of planting an effective means of replenishment. The aerial root is the mechanism that will ultimately secure the plant making it resistant to environmental factors that would under normal conditions prohibit development at many potential replenishment sites. The support provided by the aerial roots will hold the trunk of mature trees above the mean high tide water level. Over time an intricate maze of roots will protrude from the stem and end the plant's dependence on the encasement for its survival. In environments that are unfavorable to the seedling's initial development, the encased method will allow the tree to reach a point where its own infrastructure can overcome factors that are hostile to the immature tree. As the plant matures it will establish a dense foundation of prop roots and will continue to develop independent of the encasement. This foundation will enable the mangrove to grow into a healthy, self-supporting tree.