Floristic Composition of Home-garden Systems in Dumbara (Knuckles) Conservation Area with an emphasis on Endemic Species

Abstract

Home gardens are multistoried ecosystems and are important not only for in-situ biodiversity conservation, but also as valuable food sources, fodder, medicine and spices. The main objective of this study was to make decisions about the variations of home garden composition and to identify the endemic species. Fifty five home gardens were studied in northern flank from January to April 2012. Two large (10x10m2) and four small (1x1m2) quadrates were studied in each home garden. Individuals . 1.5 m height and . 1 cm DBH were measured to calculate IVI. Species identification was done on site and further at the National Herbarium, Peradeniya. Total of 1335 individual woody-perennials and 4603 herbs were found in 11,000 m2 of study area. One hundred and fifty two woody-perennial species (19 endemic, 44 naturalized exotics, 37 cultivated and 52 timber) under 54 families and 56 herb species (46 medicinal) belonging to 33 families were recorded. Euphorbiaceae was the dominant family with 15 species, followed by Fabaceae (11 species), Anacardiaceae (10 species), Rutaceae (10 species), Myrtaceae (7 species), Rubiaceae (6 species), Arecaceae (6 species), Moraceae (5 species), Sapindaceae (4 species) and Zingiberaceae (4 species). Highest number of plant families (43) was recorded in Pitawala, while the lowest number of plant families was recorded in Polommana (24). Based on the Importance Value Index (IVI), the species to pay highest priority for conservation were selected. According to Shannon diversity values for different villages, Rathninda is the most stable and less disturbed, whereas Polommana is the most unstable and highly disturbed village. There were five endemic Anacardiaceae species (Campnosperma zeylanicum, Mangifera zeylanica, Semecarpus coriaceae, Semecarpus nigro-viridis, Semecarpus walkeri). Twelve percent of the studied population were interested in timber trees such as Tectona grandis, Melia azedarach, Swietenia macrophylla and Chloroxylon swietenia. Twelve percent of the studied population preferred fruit trees while 5% were interested in some medicinal plants. Preference of this nature indicates that in the future, the plant diversity in these home gardens is likely to decline considerably. This might even lead to the extinction of rare, endemic plant species. Therefore, people in northern flank encouraged to incorporate multipurpose endemic plants and plants with less IVI values in their home gardens in order to maintain high diversity and to conserve endemic and relatively rare plants while gaining substantial income through their home gardens.