Floristic Diversity , Vegetation Analysis and Threat Status of Plants in Various Forest Types in Dharmapuri Forest Division , Tamilnadu , Southern India

The present paper deals with the study conducted to know the floristic diversity assessment and vegetation composition analysis in various forest types of Dharmapuri Forest division situated in Eastern Ghats of Southern India in the state of Tamilnadu. A total of 352 species of 233 genera and belonging to 79 families were recorded. The quantitative features such as density and important value index (IVI) varied greatly among forest and different forest types. In the present study the diversity index of shrubs and herbs were found to be higher than the tree species. The presence of high number of higher girth class of tree species and low number of sapling and seedling indicates that the present forest is old and exhibiting the low regeneration.


Introduction
Tropical forest constitutes the most diverse plant communities on earth and it cover's 7% of the earth's land surface, but harbor more than half of the world's species (Wilson, 1988), and are currently vanishing at an overall rate of 0.8-2% per year (May and Stumpf, 2000;Sagar et al. 2003;Naidu and Kumar, 2015).The vanishing of tropical forests comes at a time when our data on their structure and dynamics is sadly not enough (Hubbell and Foster, 1992).Dependence on forest is inevitable in India, therefore, the pressure on forests by the ever-increasing population in logarithmic (Jayakumar et al., 2002;Pragasan, 2010).Rapidly dwindling biodiversity levels have raised the concern that species loss could sooner or later lead to ecosystem collapse (Naeem and Wright, 2003); a decade of research has highlighted generally a positive relationship (Hooper et al., 2005;Balvanera et al., 2006).India is one of the 12 mega diversity countries in the world.Across the world, 25 hot-spots have been identified on the basis of the species endemism and degree of threat through habitat loss (Mayers et al., 2000).Among the rich biodiversity hot spot areas in India are such as the Eastern and Western Ghats, Western and Eastern Himalayas and Andaman islands.The present study site falls within the Eastern Ghats.
Hence, the conservation of biological diversity has become a major concern, for much of the society and many government agencies at all levels (Kaya and Raynal, 2001).Documenting basic patterns of biodiversity are fundamental for shows potential areas for conservation and management action (Villasenor et al., 2007).The Eastern Ghats of India is a broken chain of hills that runs almost parallel to east cost of India covering four states viz.Odisa, Andhra Pradesh, Tamilnadu and Karnataka.Floristic diversity and phytosociological study of Dharmapuri forest Division is lacking.Therefore, the present study has been undertaken to assess the plant biodiversity and vegetation analysis in different forest types of Dharmapuri Forest Division.

Study area
The Dharmapuri Forest Division lies between 11 o 53' and 12 o 29' N and 77 o 40' and 78 o 17' E. It occupies the entire Dharmapuri, Pennagaram and Palacode Talukas.The total area of this division is 9,6407 ha.The headquarters of this division is at Dharmapuri.There are four territorial forest ranges (Pennagaram, Hogenakkal, Dharmapuri and Palakkodu) in this division.circumference in each quadrat was measured and recorded for each species.The Important Value Index (IVI) for the tree species was determined as the sum of the relative density, relative frequency and relative dominance (Simpson, 1949;Curtis, 1959).The species diversity among forest types were determined by using Shannon Wiener information function (H') (Shannon and Wiener, 1963).Similarity index was determined by as per formula given by Sorenson (1948).

Compositional features Southern tropical dry mixed deciduous forest
This is the most conspicuous type of deciduous forest in the division spreading over almost all the reserved forests of Palacode and Bevanurmalai of Pennagaram Range.Sandal and Bamboo, the two economically most valuable species are found exclusively in this forest.The species forming the upper and lower canopy are almost deciduous.Some of the predominant trees that are found to occur in this forest type are: Albizia amara, Acacia planifrons, Anogeissus latifolia, Chloroxylon swietenia, Psydrax dicoccus, Cassia fistula, Holoptelea integrifolia, Phyllanthus emblica, Premna tomentosa, Vitex altissima, Cassine glauca, Diospyros ferrea, Strychnos nuxvomica, Shorea talura and Ficus spp.. Shorea talura though occurs profusely in this sub type, but only in patches.The most common climbers/liana/straggler in this forest is: Cissus quadrangularis, Cocculus hirsutus, Scutia myrtina, Cryptolepis grandiflora, Jasminum spp., etc.The common herbs here are Spermacoce ocymoides, Evolvulus alsinoides, Oplismenus compositus, Aristida setacea etc.
The rainfall is low with annual average of only 846 mm and varies within the narrow limits from 736 to 1,054 mm.
The division covers a vast table land supported by hill ranges clothing its boundaries on the west, south and east.According to the revised survey of the forest types of India by Champion and Seth (1968), the forest division is represented by 12 different forest types (Fig. 1).

Survey, sampling, data compilation and analysis
Survey was conducted during 2013-2015 covering all aspects and different seasons.For the study of plant biodiversity the division is divided based on 10 different forest types.These forest types were further separated depend on topography and altitude.Intensive field survey adopting 0.1% of the total area of each forest types was carried out following quadrat technique.For the quantitative assessment, a plot of 31.62 × 31.62 m. (65 nos.) quadrats for trees, bamboos and lianas, all the individuals were measured at GBH in the sample plots; within which 5×5 m (130 nos.) quadrats for shrubs, saplings and climbers and 1×1 m (260 nos.) quadrats for herbs and seedlings.For the collection of data from these quadrats and analysis, standard ecological methods were followed.A species list of all the identified species was prepared with the help of flora guides (Hooker, 1872(Hooker, -1897;;Gamble andFischer, 1915-1932;Vajravelu andRadhakrishnan 1967-1968;Matthew, 1981Matthew, -1984;;Ahmedullah and Nayar, 1987;Henry et al., 1987;Henry et al., 1989;Sanjappa, 1992;Nayar, 1996;Jagtap and Singh, 1999;Singh, 2001;Balakrishnan and Chakrabarty, 2007;Ansari, 2008).Each sampled sites were marked with a Global Positioning System (GPS).
Southern Euphorbia Scrub: This is an extremely degraded type of forest seen in pockets along the fringes of the Carnatic Ambrella Thorn Forests.No noteworthy tree growths are seen here.The vegetation comprises mostly Euphorbia antiquorum, Euphorbia tortilis with Albizia amara, Azadirachta indica and Annona squamosa.Some of the worthy species to be mentioned in this forest type are: Coccinea indica, Caralluma spp., Rhynchosia minima, Sida spp., Commiphora berryi, Dioscorea spp., Cardiospermum halicacabum, Barleria buxifolia, etc.

Species diversity and concentration of dominance
The species diversity, concentration of dominance of different forest types are depicted (Table 2).The highest concentration of dominance was recorded for HwkF (0.05) followed by RvF (0.03) and for all other 8 forest types is 0.01.The species diversity (H) was recorded highest for CUTF (5.28) followed by STF (5.22) and the lowest for HwkF (3.00).

Native, rarity and endemic species
Of the recorded species Twelve (12) species are endemic to peninsular India (Nayar and Sastry, 1990;Ravikumar and Ved, 2000); remaining species are non natives and Twenty one (21) species were rare for Peninsular India.Among threatened and near threatened category Three (03) species are Endangered (EN), Two (02) species are Rare and Two (02) species are Vulnerable.CUTF and STF forest represents maximum numbers (19 each) of threatened species viz.Endemic, Endangered, Rare and Vulnerable.Other forest types signify less number of threatened species.
The biodiversity on earth provides a large number of services to humankind.Biodiversity not only helps in the regulations of soil, water but it also provides food and shelter for survival.Due to increase in human population, has resulted in demand of more and more biological resources (Daily, 1995;Singh, 2002).These resources are limited and for the sustainable exploitation of these resources we have to formulate some strategies.Such activities are impairing and destroying ecosystems.For conservation and management of these species in wild an attempt have been made to assess and identify the status of diversity in Junction of Eastern and Western Ghats.The assessment was done by using the quantitative and qualitative attributes.Tree density significantly contributes to the forest functional diversity, ecological processes and ecosystem services (Puttookame et al., 2015).Tree species richness in Bannerghata forests ranged from 9-41species (Verma et al., 2009).In Mudumalai Forest in India has 63 tree species (Condit et al., 2000) and in present study area 51 species which is less then Mudumalai but higher then Bannerghata Forests .The five most abundant families in DFD were Fabaceae (34 nos.), Acanthaceae (24 nos.), Poaceae (22 nos.), Euphorbiaceae (17 nos.) and Rubiaceae (16 nos.), while Panda et al. (2013) found Euphorbiaceae and Moraceae to be the most dominant families in the northern portion of Eastern ghats, in southern portion of Eastern ghats in Bannerghata Forests is dominant by families Fabaceae, Caesalpiniaceae and Rubiaceae (Puttookame et al., 2015;Gopalkrishna et al., 2015), Mimosaceae, Rubiaceae, Apocynaceae were the most dominant families in Piranmalai Forest (Pitchairamu et al., 2008), Euphorbiaceae and Rubiaceae were most dominant in Shervarayan hill (Kadavul and Parthasarthy, 1999).

Conclusions
Economic well being of human is directly connected to its surrounding biodiversity and is an essential ingredient of ecosystem function and its stability.The floristic diversity of Dharmapuri forests will help forest department to develop management plan for these tropical dry forests of Eastern Ghats.The quantitative biodiversity data of Eastern Ghats will be useful in forest management and conservation.In view of this study it shows the tree density in forests along with the rare and endemic species of the forest division.During our study period we have observed that all the forested area of this division was subjected to continuous biotic pressure resulting into rapid degradation.With the help of JFM concept these areas can slowly be restored for recouping the vegetation.Due to perpetual grazing as observed in many areas, the new seedlings and saplings of important species like bamboo, medicinal plants and other NTFP species are often subjected to continuous damage.Management of grazing is very important for the conservation of natural vegetation.This will help to increase in availability of biomass for fodder, fuelwood in forest areas.With the help of this studies it has been identified the specific localities of each of CR/EN/VL species for this division and these localities can be further monitored to know their population dynamics and based on this a special conservation plan can be made and it should also be included in the working plan for their conservation in its respective habitats.To accomplish the success, a nursery can be raised close to the well identified forest area and these CR/EN/VL plants can be grown there and shall later be transferred to the specific natural habitats.
The study area is dominated by Southern Tropical Dry Mixed Deciduous forest, Hardwickia subtype, Secondary Dry Deciduous Forest, Dry Deciduous Scrub, Dry Tropical Riverine Forest, Southern Thorn Forest, Southern Thorn Scrub Forest, Dry Bamboo Brake, Carnatic Umbrella Thorn Forest and Southern Euphorbia Scrub.

Table 2 .
Species diversity in different forest types Carnatic umbrella thorn forest; DDS: Dry deciduous scrub forest; EuS: Euphorbia scrub forest; HwkF: Hardwickia forest; RvF: Riverain forest; SDDF: Southern tropical dry deciduous forest; SDMDF: Southern tropical dry moist mixed deciduous forest; SDS: Southern scrub forest; STF: Deccan thorn forest and STS: Deccan thorn scrub forest.Appendix 1. Diversity of plants in the sample quadrats for various forest types in Dharmapuri forest division with reference to their threat status List of species recapitulation in forest types of Dharmapuri Forest Division.