ASSESSMENT OF ECOLOGICAL STATUS OF ECONOMICALLY IMPORTANT PLANTS IN UDHAYAGIRI HILLS, NAGARCOIL

The present ecological investigation was carried out in the understorey of tropical moist deciduous forest of Udhayagiri fort hills, Kanyakumari, Tamil Nadu. A total number of 171 species were documented in the understory of the study area and among them 163 species were recognized as economically important. The secured value of ecological attribute, importance value index (IVI) indicates that the species like Tephrosia purpurea, Clerodendron infortunatum Acalypa indica, Aerva lanata, Asystasia gangetica, Belpharis maderaptensis, Cleome viscosa, Dodonia viscose, Glycosmis pentaphylla, Leucas aspera, Limnophila indica, Martynia annua, Oldenlandia umbellate, Pavetta indica, Phyllanthus amarus and Rhynchosia minima are well established in the study area. On the other hand, 55 plant species are considered to be ecologically weaker in the community. Hence priorities must be given to these species for natural regeneration and hence their conservation as well.


INTRODUCTION
Western Ghats is among the ecologically richest of India, next to the Himalaya in the diversity of its biological species (Gadgil, 1984). It encompasses many types of ecosystems such as tropical wet evergreen forests, dry deciduous forests, moist deciduous forests, thorny scrub jungles and the fragile montane shoals with associated grasslands (Champion and Seth, 1968). Among the different types of vegetations in the Western Ghats, The present study area, Udhayagiri Hills is dominated by the tropical moist deciduous forests. A large number of herbs, shrubs and climbers is commonly occupying in the under storey of the study area. Udhayagiri Hills under semi -arid climatic condition in many parts hold more number of economically and medicinally important plants due to the presence of diverse secondary metabolites. However, works on phytosociological analysis in the understory of this region have been and lies at a distance of 14 km from the town of Nagercoil. The Udhayagiri covers a huge area of 22.50 hectares which is surrounded by isolated hills. The elevation of the study area is 97m above msl. The geographical location of Udhayagiri fort hills lies between 8° -14' 38.4 N attitude and 77°-19' 55.2 E longitude.

Experimental methods
Phytosociological analysis was carried out during the rainy month of September, 2013 in the understory of the study forest, Udhayagiri hills. At the time of sampling, 50 random quadrats each with the size of 1m 2 were laid to encount the species and their individuals. The quantitative characters such as frequency, density, abundance, relative frequency, relative density, relative dominance and importance value index were calculated according to the following formulae proposed by Cottam and Curtis (1956): Number of quadrats in which the species present limited. Hence, the present ecological investigation was carried out to enlist economically important

Study area
The present study area, Udhayagiri fort hills is situated in the Kanyakumari district of Tamil Nadu Since most of the stems are cylindrical, the basal area was calculated by using the formula: Basal area = πr 2 Where, π = 3.14 and 'r' is the radius of the stem at the point of emergence.
Relative frequency, relative density, and relative dominance were calculated from the following formulae: Number of occurence of the species Croton zeylanicus, Crotalaria pallida, Curculigo orchioides, Plumbago zeylanica and Rauvolfia serpentina have exhibited poor distribution. The external factors like topography, soil conditions and the biotic disturbance and some intrinsic factors like dispersal mechanism, longevity of seeds, duration of dormancy and germination efficiency are some of the environmental variables generally determine the degree of distribution of any plant species (Belsky, 1988).

The plant species such as Tephrosia
Relative dominance (%) = Total basal area of the species Total basal area of all species X 100 purpurea, Acalypa indica, Aerva lanata, Asystasia gangetica, Belpharis maderaptensis, Cleome viscosa, Importance value Index (IVI) is the sum of quantities of relative frequency, relative density and relative dominance expressed per 300.

RESULTS AND DISCUSSION
A total number of 171 species were documented in the understory of the study area and among them 163 were recognized as economically important (Table 1). This may be explained that the study area has favourable microclimate for better growth and development of more number of species and also potential habitat for the plants of economic importance. Puri et at (1989) stated that the continuous availability of moisture in the soils of shoals in Western Ghats enables the appearance of more number species. Despite the presence of suitable microclimate, the constituent species in the understory of shoals in Western Ghats showed wide variation in distribution level, population size and basal area between them (Padmavathy, 2005).
In the present study, the ecological position for highly and poorly established plants alone is highlighted in terms of expressing their frequency, density, basal area and importance value index ( Table 2). The dicot species such as Acalypa indica, Asystasia gangetica, Cleome viscose, Leucas aspera, Phyllanthus amarus and Sida cardata showed maximum frequency value of 100% in the community and certain other herbaceous species viz., Aerva lanata, Belpharis maderaptensis, Mollugo pentaphylla, Oldenlandia umbellate, Stylosantus hamate and Tephrosia purpurea also showed higher distribution (around 85% frequency value) during rainy month of September. The higher seed output and greater reproductive potential exist in these species may be the possible reasons for this fact (Usher, 1991).
Many species in the understory of the study area like Amaranthus spinnosus, Amaranthus virigidis, Barleria buxifolia, Biophytum sensitivum, Clerodendron infortunatum, Leucas aspera, Phyllanthus amarus, Sida cardata, Mollugo pentaphylla and Oldenlandia umbellata were present in the study area with higher densities. This may be due to the presence of continuous wetness, a favourable factor for the better growth of these species in the soil of moist deciduous forest (Saxena, 1991 , have always present with low densities in the study area. The poor reproductive potential with less seed output and weaker competitive ability may lead the species with low density in the communities (Chandrasakaran and Swamy, 1995).
The basal cover of certain plant species such as Tephrosia purpurea, Clerodendron infortunatum, Acalypa indica and Pavetta indica was greater in the understory of studied forest. Among them, due to shrubby habit two species namely Clerodendron infortunatum and Pavetta indica were occupied higher basal cover in comparison to other constituent species. This feature may lead to the occupation of higher basal cover in the communities. The lower basal cover attained by many species such as Aerva javanica, Alternanthera sessilis, Asparagus racemosus, Centella asiatica, Clitoria ternate, Desmodium adscendens, D. triflorum, Evolvulus alsinoides, E. nummularis, Indigofera hirsuta, I. glandulosa, Justicia gluca, and Oldenlandia corymbosa might be due to their poor ecological characters like lower density and less basal area per individual.      and S. hispida were weaker in ecological attributes and secured poor IVI in the communities of studied forest. In addition to less fitness, the killing of young individuals by frost in winter may be ascribed as reason for this fact (Agarwal et al., 1961). Hence it is suggested that priority must be given to these species for conservation by employing proper macro micro propagation techniques.