Department of Geography, University of Colombo.
Sri Lanka is relatively a small island in size with only 65,610 km
of land and its
diversity in faunal and floral species. Vegetation analyses have recognized fifteen
different floristic regions (Figure-1) within the country (Aston and Gunathilleke,
1987) having 3360 plants species belonging to 1070 genera and 180 families (Peeris,
1975). A remarkable feature in floristic diversity seen in Sri Lanka is that, 90% of its
endemic species are confined to the rain forests found in the west zone, having a land
area of 15000km
. It is a reflection of the island's separation from the Indian
Although, the south western part of the island represents a significant diversity in
flora, a large proportion is also found in that region in wet zone of the island. Thus,
human activities altered the areas covered by forests since historic periods
through their multiple activities, include agriculture, livestock, industry, living space
and recreation etc. The human activities and practices undertaken in converting
natural forests exert a definite impact on the fragmentation of large forest areas and it
has been decreased significantly in last few decades. Transformation into secondary
forests and isolated plots duly has raised an adverse impact on the floristic richness in
the island to a grater degree. Especially the extensive deforestation in the wet zone
has put most of endemic species top in the extinction list.
Therefore, an assessment floristic diversity and analysis of vegetation
isolated forests found in the wet zone has been identified as a fact of great importance
and a needy investigation. Exploration of Salgala forest reserve, which is in fact an
isolated floristic patch, would be of great help to disclose the phytosociological
information and phytogeographical distribution, which were never been explored and
made known so far. The richness of information and understanding of a particular
ecosystem helps to extend innovative and environmental friendly planning and
OBJECTIVES OF THE STUDY
Several problems arise with regard to the floristic diversity and types of vegetation in
an isolated forest patch. First, the type of floral species in that forest, second what
would be the abundance species in the forest, third the nature of the floristic diversity
and its spatial distribution, fourth what are the uses and advantages of forest, what
study, an attempt was made to address the first of these problems. Therefore, the
objective of the study was to
Find out the abundance species of the forest
Identify the spatial differences of floristic diversity of the forest.
Figure-1: Floristic regions of Sri Lanka
Salgala forest reserve encompassing an extent of 127.8ha is located at Galapitamada
area in the Kegalle district Sri Lanka.
he forest is located between 7
6' 48''and 7
14' 65'' and 80
15' 48''longitude E. (Figure-2) It was named as
a forest reserve in 1817.
Mean elevation of the study area is 250 m and there are two small hills more than
320m in height in the central and the southern parts of the forest. The maximum
height of the study area is about 330m while the lowest is about 100m. The slope of
the terrain varied between 5%-45% and relatively a steep slope can be seen in
southern part. The rock type was Highland series (Coorey P.G, 1964) and major soil
type in the area is Red Yellow Podsolic (Panabokke C.R, 1967). Average annual
rainfall is 2000mm-4000mm. Mean annual temperature fluctuates between 25oC –
27oC which are typical climatic features of the “wet zone”. Over 75% of surrounding
area of the forest, is covered by Rubber, home gardens and paddy revealing the
potentiality of human influence to the forest reserve.
Source: Gunathileke I.A.U.N and Gunathileke C.V.S, 1990
Figure-2: Location of Salgala Forest reserve
The study is basically depending on primary data collected by a field survey.
The forest area was divided into three main zones; north, central and south according
to the density of the forest based on the interpretation of a 1:5000 aerial photograph.
Vegetation sampling was carried out in three transects within each zone. (Figure-4
and Table-1) Located sample size is 10m X 10m and the gap between each contiguous
samples were 200m. 19samples were selected maintaining topographic heterogeneity.
Over 10cm girth at breast height (GBH) trees were enumerated.
Following phytosociological data from each sample were collected
Number of species.
Local name of the species.
Scientific name of the species.
Life form of the species.
Diameter at the breast height of each species.
species diversity and family diversity. Abundance diversity index was calculated to
identify the abundance species and abundance families in the forest. A principal
component analysis was done to explore the spatial differences and phytosociological
factors affecting the spatial variation of floristic diversity in the forest.
Salgala Forest Area
Figure- 4: Flow diagram for preparation of base map for the field survey
Table -1: Details of vegetation transects
Total number of 886 tree individuals over 10cm GBH were enumerated. A total of 51
species, 29 families and 22 endemic species were recorded. (Table-2)
Enlarged Aerial photo
Base map of the study area for the
Classification of the
forest area according to
Location of transects and
Table-2: Phytosociological data of the forest
Family of Species
Wal jambu (Z
Wal del* (Z
Mal laulu* (Z
Path keala* (Z
Goda para* (Z
Wal duriyan (Z
Mal kera* (Z
Muna mal (Z
Balu nakutu (Z
Katu kela (Z
) – Could be only seen in Zone-1
) - Could be only seen in Zone-1
) – Could be seen in both Zone-1 and Zone-1 * - Endemic species
Table-3: Data on floristic families, species and endemic species at different levels of
* Based on total number of species 51
** Based on total number of endemic species 22
*** Based on total number of families 29
A large number of species could be seen within the elevations of 221 – 260 m and 261
of species were identified at the elevation of 181 – 220 m. Mastixin tetrandra and
The largest number of endemic species were seen at the elevation of 261 – 300 m
where 18 (82%) out of a total 22 endemic species were recognized. Other elevations
were nourished with relatively lower percentage of endemic species. (Table-3)
Both 221 – 260 m and 261 – 300 m elevations claim for highest number of families,
each area containing 26 (90%) out of a total of 29 families. A fever number of
floristic families 17 (59%) out of 29 were identified at the elevation of 181 – 220 m,
compared to the other elevations.(Table-3)
Figure Distribution of the floristic diversity of
Salgala forest reserve
Based on Field survey and GIS,
SPATIAL DIFFERENCES OF FLORISTIC DIVERSITY OF THE FOREST
A rich floristic diversity could be seen in the zone-1 (Z
) (Figure-3). Total number of
. 15 of the species out of 48 were restricted to the Z
There were 23 endemic species and 6 were confined to Z
There were 27 families in
and 5 families were confined to the area. Aporosa lindleyana was the most
) (Figure-3). Total number of 37
and 2 families were confined to the area. Hamboldtia laurifolia was the most
abundant species type in the Z
The best floristic richness could be seen at the elevation area of 221 – 260 m and 261
– 300 m. The least floristic richness could be seen at the area of 181 – 220 m.
The forest area could be classified into two major zones based on the Principal
Component Analysis method. Highly rich floristic diversity could be find out in Zone-
1 while relatively a low floristic diversity revealed in Zone-2.
I am greatly indebted to Mr. H.K.N.Karunarathne my supervisor -final year thesis,
whose encouragement, guidance and support from the initial to the final level of this
exercise and his dedication in teaching.
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