208
D. S. Gandhi and S. Sundarapandian
as observed in this study could be largely due to seasonal variation i.e. hot summer
(herbaceous vegetation is completely dried off and rejuvenate in rainy season) and
overgrazing. The shrub species richness is low in few study plots, owing to tree species
dominance. The presence of Lantana camara, an alien weed, in all the studied plots
indicates that it would have probably invaded the Sathanur reserve forest several
years back and had successfully established itself (Behera and Misra 2006). The low
density of herbaceous vegetation in the inner plots is because of low insulation on
the forest floor as the canopy is closed.
The species diversity is dependent on the capability of species to adapt, which
increases as the community becomes more stable. Species diversity is brought about
by species interaction like competition as well as niche variation (Pianka 1966),
which are prominently expressed in the tropical regions because of high temperature
and humidity (Ojo and Ola-Adams 1996). Shannon’s index is generally higher for
tropical forests (Knight 1975), whereas in Indian forests, the reported range was
0.83–4.1 (Singh et al. 1981; Sundarapandian 1997). In the present study, Shannon’s
index value ranged from 0.716–2.343 for tree species; 0.812–1.948 for shrubs; 1.157–
2.8 for herbs and 0.243–2.796 for climbers. It is very difficult to compare diversity
indices due to variations in the sampling location and uneven plot dimensions. The
greater dominance index could be due to the mono-species dominance exhibited by
Albizia amara in this forest ecosystem.
The density of species is directly dependent on species richness (Denslow 1995;
Condit et al. 1998). The extent of tree density contributes as much to the forest’s
functional diversity, ecological processes and ecosystem services (Gopalakrishna
et al. 2015). The mean tree density of 584 stems/ha registered in the present study is
closer to the Amazonian average (597 stems/ha; Lewis et al. 2004) and Bornean (Asia)
average (602 stems/ha; Slik et al. 2010), and 28.8% higher than the tropical forest
average (425 stems/ha; Lewis et al. 2013) of Africa. Similarly, the value recorded in
the present study is in line with those reported by Pragasan and Parthasarathy (2010)
in the southern Eastern Ghats (457 stems/ha); Reddy et al. (2008b) in Similipal
biosphere reserve (568 stems/ha) and Sahu et al. (2007) who reported 591 stems/ha in
tropical dry deciduous forest, Odisha. However, the mean tree stem density values in
the present study are lower than the findings of Kadavul and Parthasarathy (1999a, b)
who reported 815 stems/ha in Shervarayan hills of southern Eastern Ghats. Similarly,
Reddy et al. (2008a, 2011) reported 735 stems/ha and 709 stems/ha respectively in
the tropical dry deciduous forest, Andhra Pradesh. The observed tree species density
in the present study is higher than the findings of Sahu et al. (2012), Premavani et al.
(2014), and Sahu et al. (2016) with 443 stems/ha, 360–526 stems/ha and 479 stems/ha
respectively in the northern Eastern Ghats. Similarly, low stand density was recorded
from other tropical forests of the world: Brazil (420–777 stems/ha; Campbell et al.
1992), Costa Rica (448–617 stems/ha; Heaney and Proctor 1990) and Malaysia (250–
500 stems/ha; Primack and Hall 1992). Therefore, the observed density of trees in
the present study can be considered modest when compared to the similar forest
types in the Indian Eastern Ghats. Tree density may be influenced by anthropogenic
activities and soil properties.
D. S. Gandhi and S. Sundarapandian
as observed in this study could be largely due to seasonal variation i.e. hot summer
(herbaceous vegetation is completely dried off and rejuvenate in rainy season) and
overgrazing. The shrub species richness is low in few study plots, owing to tree species
dominance. The presence of Lantana camara, an alien weed, in all the studied plots
indicates that it would have probably invaded the Sathanur reserve forest several
years back and had successfully established itself (Behera and Misra 2006). The low
density of herbaceous vegetation in the inner plots is because of low insulation on
the forest floor as the canopy is closed.
The species diversity is dependent on the capability of species to adapt, which
increases as the community becomes more stable. Species diversity is brought about
by species interaction like competition as well as niche variation (Pianka 1966),
which are prominently expressed in the tropical regions because of high temperature
and humidity (Ojo and Ola-Adams 1996). Shannon’s index is generally higher for
tropical forests (Knight 1975), whereas in Indian forests, the reported range was
0.83–4.1 (Singh et al. 1981; Sundarapandian 1997). In the present study, Shannon’s
index value ranged from 0.716–2.343 for tree species; 0.812–1.948 for shrubs; 1.157–
2.8 for herbs and 0.243–2.796 for climbers. It is very difficult to compare diversity
indices due to variations in the sampling location and uneven plot dimensions. The
greater dominance index could be due to the mono-species dominance exhibited by
Albizia amara in this forest ecosystem.
The density of species is directly dependent on species richness (Denslow 1995;
Condit et al. 1998). The extent of tree density contributes as much to the forest’s
functional diversity, ecological processes and ecosystem services (Gopalakrishna
et al. 2015). The mean tree density of 584 stems/ha registered in the present study is
closer to the Amazonian average (597 stems/ha; Lewis et al. 2004) and Bornean (Asia)
average (602 stems/ha; Slik et al. 2010), and 28.8% higher than the tropical forest
average (425 stems/ha; Lewis et al. 2013) of Africa. Similarly, the value recorded in
the present study is in line with those reported by Pragasan and Parthasarathy (2010)
in the southern Eastern Ghats (457 stems/ha); Reddy et al. (2008b) in Similipal
biosphere reserve (568 stems/ha) and Sahu et al. (2007) who reported 591 stems/ha in
tropical dry deciduous forest, Odisha. However, the mean tree stem density values in
the present study are lower than the findings of Kadavul and Parthasarathy (1999a, b)
who reported 815 stems/ha in Shervarayan hills of southern Eastern Ghats. Similarly,
Reddy et al. (2008a, 2011) reported 735 stems/ha and 709 stems/ha respectively in
the tropical dry deciduous forest, Andhra Pradesh. The observed tree species density
in the present study is higher than the findings of Sahu et al. (2012), Premavani et al.
(2014), and Sahu et al. (2016) with 443 stems/ha, 360–526 stems/ha and 479 stems/ha
respectively in the northern Eastern Ghats. Similarly, low stand density was recorded
from other tropical forests of the world: Brazil (420–777 stems/ha; Campbell et al.
1992), Costa Rica (448–617 stems/ha; Heaney and Proctor 1990) and Malaysia (250–
500 stems/ha; Primack and Hall 1992). Therefore, the observed density of trees in
the present study can be considered modest when compared to the similar forest
types in the Indian Eastern Ghats. Tree density may be influenced by anthropogenic
activities and soil properties.