Species diversity in the tropics varies dramatically from place
to place. Compared to other tropical forest types, dry deciduous forests
are among the most exploited and endangered ecosystems of the biosphere
(Murphy and Lugo, 1986; Janzen, 1988; Gentry, 1992).
The Indian subcontinent, with its rich biodiversity, is one of the 12
mega-diversity centers of the world. The Eastern Ghats, the Western Ghats
and the north eastern hills are the main biodiversity hotspots of India.
Primary forests of Asia, particularly those of the Western Ghats and the
Eastern Ghats of peninsular India are disappearing at an alarming rate
due to anthropogenic activities and are replaced by forests comprising
inferior species or their land use pattern changed (Bahuguna,
1999). Studies from Forest Survey of India showed an average of
54.7% of forest is affected by fire and 72.1% of the forest area is subjected
to grazing. Annually 3.73 million hectares of the forest area are burnt
resulting in economic losses of approximately 440 crores (Anonymous, 1990).
Information on floral composition, diversity and biomass are absolutely
essential in understanding the forest ecosystem dynamics and conservation.
It may become a tool to estimate the level of adaptation to the environment
and their ecological significance (Pascal and Pelissier, 1996). Tropical
dry deciduous forests are enriched with economically important species.
Vegetation composition, diversity of species and their habitats are well
understood for other tropical forest types compared to dry deciduous forests.
In Eastern Ghats of India, few quantitative phytodiversity inventories
are available from the forests of Eastern Ghats of Tamil Nadu (Kaduvul
and Parthasarathy, 1999a, b; Jayakumar et al., 2002; Natarajan
et al., 2004). These kinds of studies are poorly explored for these
aspects in the State of Andhra Pradesh, which covers a major part of Eastern
Hence, the present study was undertaken to determine the structure and
floristic composition of tree diversity within a three 1 h plots in tropical
dry deciduous forests of Eastern Ghats of southern Andhra Pradesh, India.
The Eastern Ghats are located along the Peninsular India extending over
1750 km with average width of about 100 km and covering the area under
11°03 to 22°03 N Latitudes and 77°02 to 87°02E Longitudes.
The Eastern Ghats are delimited in the north by Similipal hills of Orissa
State. The middle section extends from River Krishna (Andhra Pradesh)
to near about Chennai city (Tamil Nadu) and includes the Nallamalais,
Nigidi, Seshachalam and Veligonda hills. The last section runs in S-SW
direction meeting the Western Ghats in the Nilgiris (Meher-Homji,
The area studied is located in the Nallamalais-Seshachalam-Nigidi hill
ranges of Eastern Ghats in southern part of Andhra Pradesh state, India
(Fig. 1). Three 1 ha plots area were established at three
different sites: Site 1 is located about 3 km from Peddacheruvu, a chenchu
tribal hamlet in Nallamalais of Kurnool district which receives mean annual
rainfall about 900-1000 mm. Site 2 is located about 4 km from Talakona,
a Yanadi tribal hamlet in Seshachalam hill of Chittoor district which
receives mean annual rainfall 800-900 mm. Site 3 is located about 2 km
from K. Kuntlapalli village, Anantapur district receives mean annual rainfall
about 600-700 mm. The rocks are of Kurnool-Cuddapah formations (quartzite
and slate formations predominate) and altitude ranges of three 1 ha plots
are in between 400 to 600 m. Thus, these study sites showed variability
in rainfall pattern even though their phytogeographic range is contiguous.
||Location map of study area
MATERIALS AND METHODS
Phytosociological data were collected in three 100x100 m quadrants which
are divided into 20x20 m subplots and were systematically surveyed for
all trees ≥10 cm girth at breast height (gbh-above 130 cm from the ground)
during September 2005 to January 2006 in Nallamalais-Seshachalam-Nigidi
hill ranges of Eastern Ghats, India. Thus data were obtained from a total
of 75 subplots (total area = 3 h). All plots sampled were representative
of the most common vegetation type in the Eastern Ghats, i.e., tropical
dry deciduous forest. The species were identified with the help of Flora
of Presidency of Madras (Gamble and Fischer, 1915-1935) and
Flora of Tamil Nadu Carnatic (Matthew, 1984).
The vegetation data were quantitatively analysed for basal area, relative
density, relative frequency and relative dominance (Phillips, 1959). The
Importance Value Index (IVI) for the tree species was determined as the
sum of the relative frequency, relative density and relative dominance
(Cottam and Curtis, 1956).
|Basal area (m2)
||Area occupied at breast height (1.3 m) = [p-(dbh/2)2].
||No. of trees of species/total number of trees of all species x100
||No. of time species occurs/total number of speciesx100
||Total basal area of a species/total basal area for all species x100
|Importance Value Index (IVI)
||Sum of relative density+relative frequency+ relative dominance
Species diversity of each forest type was determined using Shannon-Weiner
Index (H) = -Sum ((ni/N) ln (ni/N)) (Shannon and Wiener, 1949; Odum,
||IVI of individual species
||IVI of all species
Concentration of dominance was also measured using the formula (Simpson,
1949): C = - S(ni/N)
where, ni and N are the same as those for the Shannon-Weiner information
Similarity between three communities was determined using Sorensons
index of similarity (Sorenson, 1948).
Local diversity was defined as the number of species found in a hectare.
Regional diversity of each hill was derived independently of our plot
data, via flora checklists that summarize historical plant collections
in the study regions (Reddy et al., 2007).
A total of 137 tree species were recorded within the 3 ha plots area,
representing 98 genera in 44 families. Mean stem density was 735 trees
ha-1 (range 674-796) and mean basal area was 11.46 m2
ha-1. Plot-wise tree species richness was 69 for site 1, 64
for site 2 and 60 for site 3 with major differences between the plots
(Table 1). Site 1 (Nallamalais) forests are more diverse
at spatial scale and all taxonomic levels than their counterparts (Table
1). There are 202 species/ha at the local scale in site 1 (Nallamalais),
along with 1541 species at the regional scale (Reddy and Rao, 2007). Within
the 3 h area the most abundant families were Euphorbiaceae and Rubiaceae,
both representing 20 species.
||Consolidated details of species inventory in the 3 ha plots
||IVI of the 10 most important species in the three sites, Eastern
Ghats of southern Andhra Pradesh
An obvious variation in representation of tree species and the proportion of
dominant species in the three sites can directly be attributed to rainfall distribution
and favourable edaphic conditions. The most frequently occurring species in
three sites was Anogeissus latifolia. In site 1 some moisture indicating
species are prevalent, i.e., Pterocarpus marsupium, Anogeissus
latifolia, Dalbergia paniculata, Lannea coromandelica and
Mitragyna parvifolia. Where as in site 2 and site 3 species composition
possess more dry elements, indicating dry habitats. In site 2, Pterocarpus
santalinus, Terminalia pallida, Anogeissus latifolia, Terminalia
chebula and Dolichandrone atrovirens and in site 3, Chloroxylon
swietenia, Albizia amara, Premna tomentosa, Anogeissus
latifolia, Ixora arborea and Diospyros chloroxylon are predominant
||Population density of tree species (≥ 10 cm gbh) in three
sites across Girth Class intervals, Eastern Ghats of Southern Andhra Pradesh
||Girth class wise basal area in three different sites, Eastern
Ghats of southern Andhra Pradesh
||Height class wise proportion of individuals in three different
sites, Eastern Ghats of Southern Andhra Pradesh
While in site 1 top most 10 species represented 56% of individuals, where as
in case of site 2 and site 3 the proportions are 65 and 62%, respectively. A
large group of species (34%) are represented by ≤2 individuals.
Site 2 represents all the seven endemic tree species of Seshachalam hill
(Pterocarpus santalinus, Terminalia pallida, Boswellia
ovalifoliolata, Syzygium alternifolium, Cycas beddomei,
Shorea tumbaggaia, Phyllanthus indofischeri). Site 1
and site 3 represents one endemic tree species each (Eriolaena lushingtonii
and Hildegardia populifolia, respectively). In addition to it site
3 shows unique representation of Santalum album (one of the costliest
scented wood of the world and known as pride tree of Eastern Ghats).
The total basal area for all stems within the 3 ha area is 34.39 m2
(Table 1). The distribution of the basal area across
the 1 ha plots, using gbh interval classes, reveals the dominance of small
stemmed individuals in the plot (Table 3). The mean diameter
of top 10 dominant tree species covers 62% of ground cover. It means minority
of species dominate the majority of the available resources (Table
Tree distribution by height intervals is shown in Fig. 2.
The mean tree height is 12 m, with a height range from 1 to 25 m. The
tallest individual trees were Pterocarpus marsupium (25 m) and
Terminalia bellirica (23 m) in site 1. In site 2, Pterocarpus
santalinus (22 m) and Terminalia pallida (21 m) are tallest.
Tree species in site 3 (Nigidi hill) show trends towards shorter stature
(49.5% of individuals are with less than 5 m height) than trees in site
1 (32.4%) and site 2 (44.4%).
The basal area and vertical structure of a forest is difficult to summarise
as these relies heavily upon the climate and edaphic conditions. Tree
heights are heavily influenced by the abundance of saplings, richness
of nutrients and anthropogenic pressure (since forest fires are recurrent).
The predominant forest type of the Eastern Ghats of southern Andhra
Pradesh is tropical dry deciduous forest (Champion and Seth, 1968). It
occupies 93% of forest area (Anonymous, 2006).
Through the use of the subset of tree individuals = 10 cm gbh, our 3
ha plot area contains 2205 individual stems representing 44 families with
137 species. The Shannon-Weiner index (H) for the 3 ha was 4.97 but varied
largely with the plot (4.89, 4.75 and 4.11), with Simpsons value ranging
from 0.92 to 0.95. These values infer that Eastern Ghats are also high
species diverse systems.
The mean stand density of 735 stems ha-1 and range of 674
to 796 stems ha-1 in the forests of southern Andhra Pradesh
is well within the range of 276-905 stems ha-1 reported for
trees = 10 cm gbh in the tropics (Murali et al., 1996; Sundarapandian
and Swamy, 1997; Ghate et al., 1998). This range of stand density
in the present study is higher when compared to the other Eastern Ghats
sites (Kaduvul and Parthasarathy, 1999a, b; Chittiibabu and Parthasarathy,
2000; Jayakumar et al., 2002; Natarajan et al., 2004).
In terms of the overall ecological dominance within our plot, the high
importance value species (IVI) are differs from site to site, except for
Anogeissus latifolia. It is commonly found (wide niched) in all
dry deciduous forests.
Species rarity (those represented by = 2 individuals) of 34% obtained
in the present study area is higher as compared to Kuzhanthaikuppam and
Thirumanikkuzhi (26 and 31%, respectively) dry evergreen forest sites
on the Coromandel coast (Parthasarathy and Karthikeyan, 1997) and
lower than that of (43%) the Kalrayan hills, Eastern Ghats (Kaduvul
and Parthasarathy, 1999).
Species similarity between different sites was studied using presence/absence
data. 39% of the species recorded are found similar between site 1 and
site 3. Site 2 and site 3 are closer having 51% common species (Table
1). The top ten predominant species with their relative dominance,
relative density, relative frequency and IVI are given in Table
In the tropical rainforest, the range of tree species count per hectare
is about 20 to a maximum of 223 (Parthasarathy and Sethi, 1997). In the
present analysis a maximum of 69 tree species per hectare has been recorded
for dry deciduous forest. The present study also supports the fact that
Euphorbiaceae and Rubiaceae are the dominant families in almost all types
of forests except the mangrove (Padalia et al., 2004).
In the present study maximum tree species diversity is obtained for the
site 1, followed by site 2. It is observed that species diversity in three
sites is positively correlated with the taxonomical studies. These studies
reported the presence of 1541 species in Nallamalais, 1450 in Seshachalam
hill and 418 in Nigidi hill (Reddy and Rao, 2007). Most of the tree species
shows random distribution.
Stem density and species richness have consistently decreased with increasing
girth class of tree species from 10 to more than 150 cm girth. The highest
number of species are encountered in the low gbh classes (10-50 cm). Species
number gradually decreases with the fall in the count of stems in higher
girth class category (Table 1 and Fig.
2). Girth class having <30 cm gbh contributed to about 37% of species
Girth class frequency showed J-shaped population structure of trees exhibited
in all the three study sites are in conformity with other forest stands
in Eastern Ghats such as Shervarayan hills (Kaduvul and Parthasarathy,
1999a) and Kalrayan hills (Kaduvul and Parthasarathy, 1999b).
Calculations of IVI have helped in understanding the ecological
significance of the species in the tropical dry deciduous forest type.
Species diversity and stem density were observed to decrease with increasing
girth class. The variability in rainfall and distinct hilly terrains of
three sites has resulted in unique species in terms of species diversity
Hence it may be concluded that Eastern Ghats are still rich in tree species
diversity, even after disturbance in terms of fire, grazing, extraction
of economic/medicinal species and invasion of exotic species. Therefore,
priority should be given to conserve Eastern Ghats, which are facing pressure
from increasing population and developmental activities.
The immediate attention on peoples participation is most essential for
effective conservation. The present study will serve as a primary input
towards monitoring and sustaining the phytodiversity of tropical dry deciduous
forests in the State of Andhra Pradesh.
We thank Dr. P.S. Roy, Deputy Director, National Remote-Sensing Agency and
Sri Ganga Raju, Chairman, Laila impex, Vijayawada for constant encouragement
and support. Thanks are also due to Dr. M.S.R. Murthy, Head, Forestry and Ecology
Division and Dr. S. Sudhakar, Scientist, Forestry and Ecology Division, NRSA.
We also thank Forest Department of Andhra Pradesh for their necessary support.