Environmental Factors Affecting Seedling Establishment of the Black Mangrove on the Central Texas Coast

McMillan, Calvin

The effects of salinity, water turbulence, water depth, and temperature on the establishment of seedlings of black mangrove (Avicennia germinans L.) on the central Texas coast were evaluated in the laboratory. Salinity was not the chief factor limiting seedling establishment, because seedlings rooted in distilled water and in salinities approaching twice the concentration of sea water. Water turbulence, either of distilled or sea water, inhibited root and seedling development. Seedlings tumbled for as much as 12 weeks showed rapid root development when subsequently stabilized. Various water depths promoted extensive root systems, but seedlings did not become established until water depth was reduced to 5 cm or less. High temperature treatment, exposure to 39° -40°C for 48 hr, was lethal to stemless seedlings, but not to seedlings with stems and roots. The results suggest that viviparous development in this A. germinans population is probably phenologically timed by environmental relations during winter and early spring as a protection against the lethal effects of the high temperatures that prevail on beaches and in shallow water during late spring and summer.

Environmental Factors Affecting Seedling Establishment of the Black Mangrove on the Central Texas Coast

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