Diversity, Stand Density and Structure of Mangroves in Panama Lagoon, Sri Lanka
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Date
2020
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Uva Wellassa University of Sri Lanka
Abstract
This study was undertaken to estimate the diversity, stand density, and structure of
mangrove flora in Panama lagoon which has identified as a location with rich mangrove
vegetation in Ampara district, Sri Lanka. Six sites covering the whole lagoon were
assessed using the transect line plots method by laying three transect lines perpendicular
to the shoreline at each site which was varying from 10 m to 40 m in length. The number
of mangrove species with the distance from the shore including their diameter (cm) and
height (m) were recorded. The individuals were categorized as trees, saplings, and
seedlings based on their diameter. The in-situ parameters of soil pH, temperature, and
salinity were measured. Five true mangrove species belong to families of Avicenniaceae
(Avicennia marina), Rhizophoraceae (Rhizophora mucronata, and Bruguiera sexangula),
Combretaceae (Lumnitzera racemosa) and Euphorbiaceae (Excoecaria agallocha) were
recorded. Avicennia marina was the most dominant species with the Importance Value of
68.65. The stand density of 475 individuals/ha represented 56% of tree density, 19% of
sapling density, and 25% of seedling density. The greatest Shannon-Weiner diversity
(1.79) was recorded in site 03 while site 06 recorded the highest Simpson’s Diversity
Index (0.83) and Pielou’s Evenness Index (0.98). Site 05 obtained the highest Margalef’s
Species Richness (1.83). Highest Basal Area of 70.28m²/ha in site 01 confirmed the
undisturbed nature of mangroves. There was a negative linear relationship between
distance from the shore and average salinity (p<0.05) and a positive linear relationship
between salinity and mangrove abundance (p<0.05). The cluster analysis depicted the
highest similarity of 90.81 for site 03 and 06 based on diversity. Lumnitzera
racemosa and Excoecaria agallocha showed the highest similarity (84.14) based on
dominance and density. The results indicated the pristine nature of Panama lagoon with
high biological diversity of mangrove flora.
Keywords: Panama lagoon, Mangrove flora, Dominance, Stand basal area
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Keywords
Environmental Science, Ecology, Biology, Biodiversity – Sri Lanka