Abstract:
The last remaining fresh water swamp forest in Sri Lanka, Waturana, (6° 37'- 6° 38' N, 80°
11'- 80° 12' E), is a peculiar ecosystem. The extent of the forest is 12 ha due to severe
anthropogenicactivities. This is the first study that analyzes the floristic data in relation to
edaphic conditions. This study was performed in two phases. First, floristic inventory was
prepared for the total forest area. Secondly, a quantitative study of vegetation and soil
characterswere performed. Quadrats of 10m x 10m were laid on a stratified random manner
in 12 localities representing different habitats. Vegetation and soil parameters were
determined using standard methods. Soil parameters and species abundance data were
subjectedto principal component analysis in order to identify the plant communities.
Totalflora enumerated 172 species which belonged to 138 genera and 74 families. Out of the
total species, 44 % were endemics. Three distinct strata of the forest could be identified
namelycanopy layer «10 m), shrub layer «5 m) and ground layer « 1 m). Most dominant
tree species was Macaranga digyna. Based on family important value index of trees, the
highest abundance was recorded for the family Euphorbiaceae. Shanon Wiener diversity
index for trees was 2.62. Most dominant sapling species was Stemonoporus moonii
(Dipterocarpaceae).Shannon Wiener index was recorded as 2.61 for saplings and as 2.80 for
seedlings.Most dominant seedling species was Calamus radiates (Arecaceae).
Pearsoncorrelation analysis of soil characters and species abundance revealed that species
abundancewas positively and significantly related to the percentage of total Nitrogen (r =
.576,P = 0.05), negatively and significantly related to pH (r = -0.714, P = 0.009) whereas no
significantrelationships observed between plant abundance and other soil parameters.
Principalcomponent analysis indicated three distinct community types with relation to plant
abundanceand edaphic factors. Forty eight plant species presented in community one that was
highlydiverse and restricted to elevated areas. Community two was found from gully areas
with boggy soil and recorded 41 plant species. Both communities one and two were having
broadrange of soil parameters where community three had very narrow ranges of edaphic
factors.Community three was restricted in elevated hillocks that were least diverse recording
31species.
Waturanashould be identified as a priority area of biodiversity conservation for its extremely
high biodiversity richness and site tenacity shown by the point endemics, though
indiscriminatehuman interference has led it to degradation. Fate of the species in this habitat
could be symptomatic of a large number of rare plant species distributed in a small
fragmented patch. The results of the present study could be useful in taking measures
pertaining to the conservation of naturally established flora in swamp forest to recognize
conservationactions and preparation of a management plan.