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Distribution and population parameters of selected tree species in Gilimale and Kithulgala Forest Reserve
By lakmali | March 17, 2010
S. S. Ranathunga and B.M.P Singhakumara
Field surveys have not been carried out in Sri Lanka to gather the population data on critically endangered tree species in their habitats. The population data on the critically endangered tree species are important to understand the present status of the population. In this study, the population data of seven critically endangered tree species were gathered.
Habitat distribution and some population parameters such as stand tables, plant community composition and structure were studied for seven Critically Endangered (CR) tree species found in the Kitulgala and Gilimale Forest Reserves, tropical lowland rainforests in the southwest part of the country. The selected species are Stemonoporus gracilis, S. petiolaris, and Balanocarpus kithulgallensis in Kitulgala and Stemonoporus gilimalensis, S. lancifolius, S. scalarinervis, and Memecylon macrocapum in Gilimale. Balanocarpus and Stemonoporus an endemic genus belong to the family Dipterocarpaceae and
Memecylon macrocapum belongs to the Melastomataceae.
Sampling of vegetation has been carried out in specific habitats for each selected Critically Endangered species. Suitable plots were identified by a reconnaissance survey and 100×5 m plots were demarcated. All the plants below 1 m of height were counted as seedlings; all the plants less than 2 cm of dbh and over 1 m of height were counted as saplings. DBH and heights of trees over 2 cm dbh were measured.
Survey data of the selected tree species are used to calculate the Important Value Index (IVI). Profile
diagrams were prepared for each tree species to show the vertical distribution in their habitats. Distribution maps of these species were prepared using digital data. Sample plots are located in 1: 10,000 digitized maps prepared by the Survey Department, Sri Lanka.
All species show patchy distribution and these patches are found in different parts of the forest topography. Stemonoporus gracilis, S. petiolaris, S. gilimalensis, S. lancifolius and S. scalarinervis show positive stand tables with reverse J distribution curves. This indicates that these populations in their habitats are healthy. Balanocarpus kithulgallensis and Memecylon macrocapum are not showing this type of curves, and more sampling has to be carried out to investigate the population structure of these two species.
All these species could be conserved by protecting their natural habitats (in-situ conservation) and only a two species (Balanocarpus kithulgallensis and Memecylon macrocapum) might need both in-situ and ex-situ conservation strategies.
S. S. Ranathunga and B.M.P Singhakumara
Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Sri Lanka.
Topics: Biodiversity, sympoisum 2009 | No Comments »