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Diversity of medicinal plants in the Mihinthale sanctuary

By lakmali | March 22, 2010

A. Herath1, C. Karunanayake1 and S. Wijesundara2

Sri Lanka contains an enormous biodiversity of medicinal plants. Flora of Sri Lanka reports that there
are 3368 angiosperms in Sri Lanka, out of which 20% are medicinal. There is a growing demand for medicinal plants in primary health care. However, the local supply of medicinal plants can not meet the
demand. About 80% of the locally supplied medicinal plants are collected from the wild. This has lead
to unscrupulous collection and destructive harvesting. Therefore, the present study focused on identifying and documenting the diversity of medicinal plants in the Mihintale sanctuary.

Since medicinal plants may be trees, shrubs, or herbs complimentary sampling techniques were used in
sampling. Quadrate sizes for each plant category was chosen according to the method described by Sutherland. Therefore 20×20m, 5×5m and 2×2m quadrates were located randomly for trees shrubs and
herbs respectively. Data on floristic composition, plant density, basal area and dominance were collected
according to the method described by Crutis and McIntosh. The DBH values of the entire data set were
used for cluster analysis (SAS 6.12). Floristic diversity and richness were analyzed using Biodiversity
professional 2.0 software package. The Basal area, Relative density and Importance Value Index (IVI)
were analyzed using SAS 6.12.

One hundred and fifty nine medicinal plant species, which belong to 111 genera and 54 families, were
encountered in the study area. Of the medicinal plant species, 48 were trees, 33 were shrubs, 42 were
herbs and 32 were vines. The dendogram between cluster sums of squares showed three distinct vegetation communities: near tank vegetation, relatively undisturbed areas and disturbed areas. Munronia pinnata (Bin kohomba) an endangered species was observed only in the relatively undisturbed community while Salacia reticulata (Kothala himbutu) a threatened species and Vernonia zeylanica (Pupula) an endemic species were observed in all three communities. The species richness of medicinal plants varied from 105 to 55 species per community, the highest being in the near tank vegetation and the lowest in the relatively undisturbed community. Shannon diversity Index (H) ranged from 3.47 to 3.08, Simpsons diversity (D) from 0.073 to 0.051 and Margalefs diversity index (Dmg) from 12.52 to 8.09. Near tank vegetation ranked first in medicinal plant diversity (H=3.47, D=0.05, Dmg=12.52) followed by, disturbed (H=3.19, D=0.073, Dmg=10.6) and relatively undisturbed (H=3.08, D=0.072, Dmg=5.20) vegetation respectively. Relative densities of medicinal plants of the three communities differ significantly (p=0.035). The total sample area contained 289 medicinal trees with stems >10cm DBH. The diameter size distribution of individuals enumerated showed that 64% of them were below 30cm diameter.

Importance value Index (IVI) of woody individuals of the identified three clusters varied from 115 to 0.69. In disturbed vegetation and relatively undisturbed vegetation one species Drypetes sepiaria showed
a significant dominance over other species. Contrastingly, in near tank vegetation nearly seven species
showed high IVI values. The disturbed site showed the highest pioneer and secondary plant species
while the highest primary species number was recorded in the relatively undisturbed communityIn
conclusion, medicinal plant diversity is very high in Mihintale sanctuary. Therefore, immediate action
should be taken for conservation. Furthermore, integration of medicinal plants into farming system is
advisable to derive economic benefits to the local community as well to minimize over exploitation.

A. Herath1, C. Karunanayake1 and S. Wijesundara2
1Department of Biologcal Science, Faculty of Applied Sciences, Rajarata University of Sri Lanka
2Department of Royal Botanic Gardens, Peradeniya, Sri Lanka.

Topics: Biodiversity, sympoisum 2009 | No Comments »

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