Ramírez Ochoa, Luisa F.

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    Factores que afectan la propagación y establecimiento de Avicennia germinans L. en ambientes degradados de regiones semiáridas subtropicales
    (2005) Ramírez Ochoa, Luisa F.; Otero Morales, Ernesto; College of Arts and Sciences - Sciences; Yoshioka, Paul; Morell, Julio; Aponte, Nilda E.; Department of Marine Sciences; Tirado, Iris
    Massive mortality in mangrove stands was reported during the 1990’s in Jobos Bay National Estuarine Research Reserve (JOBANNER). At the present the recruitment and growth of Avicennia germinans seedlings are negligible. This work strives to examine biotic and abiotic factors that affect recruitment and development of A. germinans in the study area. Long-term mangrove cover at JOBANNER was examined in aerial photographs between 1963 and 2002 as part of ancillary effort to quantify the decline of mangrove. Density of A. germinans, inundation level, temperature and salinity in water and sediments were measured during a year along transects oriented perpendicular to the coastline. Two transects were located in the mortality area known as Mar Negro and the third at an eastern control station within JOBANERR named Aguirre. Seed production from June-December was estimated and seeds retention was assessed in June and September-December. The growth and survival of A. germinans seedlings in a nursery cultivated at salinities of 0, 35, 65 and 95 (practical salinity) were evaluated. Surviving seedlings from different salinities were replanted in Mar Negro and Aguirre. The development of seedling in treatments of different light exposure as well as the use of PVC tubes as protection against flooding was examined. During the first week of transplant the larvae of the lepidopteron Junonia evarete was found feeding on seedlings, thus observations related to the larvae were included in the study. Results indicate a 50% loss of mangrove cover between 1963 and 2002. Under natural conditions seedlings were found at maximum salinities of 131 and 124 in Aguirre and Mar Negro, respectively. In contrast, seedlings grew under nursery conditions at salinities up to 65. Natural recruitment was 0.45 and 0.1 seeds/m2/year at Aguirre and Mar Negro, respectively. The greater seed production occurred in Aguirre and the rate of seed loss was 2 seeds/m2/day in both sites. Overall, seedlings exposed to sunlight all day and protected against flood with PVC tubes survived and grew better in both sites, although growth was higher in Mar Negro. This study concludes that recruitment in JOBANEER is restricted by the low production and retention of seeds. The survival of seedlings during the wet season is related to the presence of moderate inundation levels thus indicating the higher survival of young plants when using PVC tubes. Herbivory from J. evarete larvae did not directly affect seedlings survival but made them susceptible to extreme edaphic conditions. Survival of 72% of seedlings at the end of the dry season in Mar Negro indicates that recolonization is possible if techniques such as cultivating seedlings, transplanting and using PVC tubes as protective barriers against inundation are used.