Plant Diversity and Distribution Pattern in Tropical Dry …
209
Top ten tree species including Albizia amara and Chloroxylon swietenia dominated the entire stand, contributing to 90.01% of the total individuals. Tree density
differences among the plots could be due to the efficiency of seed dispersal and
its establishment as well as resource exploitation levels by locals as suggested by
Kadavul and Parthasarathy (1999a). Nevertheless, mono-dominance of species like
Albizia amara in all the study plots shows their inherent ability to thrive in varied
environmental conditions and in disturbed areas.
The mean basal area of tree community was 18.71 m
2 /ha in dry deciduous forests
of Sathanur reserve forest that is modest when compared to the dry tropical forest
in Vindhyan hills (Jha and Singh 1990). The value (7.22–43.05 m
2 /ha) obtained in
the present study is well within the range of tropical dry forests in other parts of
India (range 7–23.2 m
2 /ha, Jha and Singh 1990; mean 29.0 m
2 /ha, Reddy and Ugle
2008; range 8.15–41.17 m
2 /ha, Sahu et al. 2008; range 8.6–26.9 m
2 /ha, Reddy et al.
2008a; range 30–39 m
2 /ha, Reddy et al. 2011; 6.86 m
2 /ha, Sahu et al. 2012; range
12.98–33.3 m
2 /ha with mean of 25.82 m
2 /ha, Naidu and Kumar 2016) and elsewhere
(Murphy and Lugo 1986; Lieberman and Lieberman 1987; Campbell et al. 1992).
However, our mean value is less than the pantropical mean of 32 m
2 /ha (Dawkins
1959), Amazonian average (29 m
2 /ha; Lewis et al. 2004), Bornean (Asia) average
(37.1 m
2 /ha; Slik et al. 2010), African average (31.5 m
2 /ha; Lewis et al. 2013)
and other forests of Eastern Ghats (Kadavul and Parthasarathy 1999a, b). Similarly,
the mean value recorded in the present study is lower than mean basal area values
reported by several others in tropical forests of Western Ghats (Singh et al. 1981;
Sundarapandian and Swamy 2000). The wide variations in the basal area among
the 30 one-hectare plots obtained in the present study indicate that these plots were
subjected to different levels of anthropogenic pressure. Exceptionally few plots have
high values of the basal area, which indicates that those plots have more mature trees
whereas, in some plots that had low basal area, there were many juveniles and very
few mature trees. This is probably due to greater biotic disturbances in the area as
suggested by Thakur (2015).
A total of 63 families were observed in this tropical dry deciduous forest. The most
speciose families are Euphorbiaceae and Poaceae, followed by Fabaceae and Rubiaceae. Interestingly, similar findings were reported by Pragasan and Parthasarathy
(2010) in tropical deciduous forests of the Eastern Ghats, where Euphorbiaceae,
Rubiaceae and Moraceae were the most dominant families. Borah et al. (2016) also
found that Euphorbiaceae was the dominant family in tropical forests of Barak Valley,
Assam. Several others also observed the similar results (Ifo et al. 2016; Naidu and
Kumar 2016). Hence, it can be noted that there is a similarity in family composition
of forests in tropical environments.
Diameter class frequency exhibited an L-shaped curve for the trees and the data
is in line with many other reports from Eastern and Western Ghats (Sundarapandian
1997; Kadavul and Parthasarathy 1999a). This is the typical characteristic of a tropical
forest. The DBH size class distribution showed a decline in the number of individuals
from lower class to higher class, indicating expanding population. The stem density
decreased with increase in diameter class of trees as observed in the present study,
which is in agreement with other reports (Lieberman et al. 1985; Swaine et al. 1987;
209
Top ten tree species including Albizia amara and Chloroxylon swietenia dominated the entire stand, contributing to 90.01% of the total individuals. Tree density
differences among the plots could be due to the efficiency of seed dispersal and
its establishment as well as resource exploitation levels by locals as suggested by
Kadavul and Parthasarathy (1999a). Nevertheless, mono-dominance of species like
Albizia amara in all the study plots shows their inherent ability to thrive in varied
environmental conditions and in disturbed areas.
The mean basal area of tree community was 18.71 m
2 /ha in dry deciduous forests
of Sathanur reserve forest that is modest when compared to the dry tropical forest
in Vindhyan hills (Jha and Singh 1990). The value (7.22–43.05 m
2 /ha) obtained in
the present study is well within the range of tropical dry forests in other parts of
India (range 7–23.2 m
2 /ha, Jha and Singh 1990; mean 29.0 m
2 /ha, Reddy and Ugle
2008; range 8.15–41.17 m
2 /ha, Sahu et al. 2008; range 8.6–26.9 m
2 /ha, Reddy et al.
2008a; range 30–39 m
2 /ha, Reddy et al. 2011; 6.86 m
2 /ha, Sahu et al. 2012; range
12.98–33.3 m
2 /ha with mean of 25.82 m
2 /ha, Naidu and Kumar 2016) and elsewhere
(Murphy and Lugo 1986; Lieberman and Lieberman 1987; Campbell et al. 1992).
However, our mean value is less than the pantropical mean of 32 m
2 /ha (Dawkins
1959), Amazonian average (29 m
2 /ha; Lewis et al. 2004), Bornean (Asia) average
(37.1 m
2 /ha; Slik et al. 2010), African average (31.5 m
2 /ha; Lewis et al. 2013)
and other forests of Eastern Ghats (Kadavul and Parthasarathy 1999a, b). Similarly,
the mean value recorded in the present study is lower than mean basal area values
reported by several others in tropical forests of Western Ghats (Singh et al. 1981;
Sundarapandian and Swamy 2000). The wide variations in the basal area among
the 30 one-hectare plots obtained in the present study indicate that these plots were
subjected to different levels of anthropogenic pressure. Exceptionally few plots have
high values of the basal area, which indicates that those plots have more mature trees
whereas, in some plots that had low basal area, there were many juveniles and very
few mature trees. This is probably due to greater biotic disturbances in the area as
suggested by Thakur (2015).
A total of 63 families were observed in this tropical dry deciduous forest. The most
speciose families are Euphorbiaceae and Poaceae, followed by Fabaceae and Rubiaceae. Interestingly, similar findings were reported by Pragasan and Parthasarathy
(2010) in tropical deciduous forests of the Eastern Ghats, where Euphorbiaceae,
Rubiaceae and Moraceae were the most dominant families. Borah et al. (2016) also
found that Euphorbiaceae was the dominant family in tropical forests of Barak Valley,
Assam. Several others also observed the similar results (Ifo et al. 2016; Naidu and
Kumar 2016). Hence, it can be noted that there is a similarity in family composition
of forests in tropical environments.
Diameter class frequency exhibited an L-shaped curve for the trees and the data
is in line with many other reports from Eastern and Western Ghats (Sundarapandian
1997; Kadavul and Parthasarathy 1999a). This is the typical characteristic of a tropical
forest. The DBH size class distribution showed a decline in the number of individuals
from lower class to higher class, indicating expanding population. The stem density
decreased with increase in diameter class of trees as observed in the present study,
which is in agreement with other reports (Lieberman et al. 1985; Swaine et al. 1987;