The flora of Karaikal district and its environment is a typical representative of the flora (both indigenous and alien) of the Union territory of Puducherry. Most of the botanists of this country take up the floristic studies of regular hilly tracts alone since there are not much disturbance to the natural vegetation as is seen in the plains. The flora of plains in our country has been neglected ever since and thus the area of the study has remained practically unexplored.
Regional and local floras are of immediate relevance not only for better understanding the patterns of plant invasion but also for explicating the processes promoting invasion at local, regional or global scales. Assessing the impact of climate change on biodiversity at local level is more accurate than national levels, because changes occur slowly and effects of climate change interact with other stress factors already imposed on the environment.
It has been pointed out that Karaikal district seems to have been considerable number of floral wealth including good number of rare and endemic plant species. Until recently no serious attempts had been made scientifically to document the plant diversity of Karaikal district. As a result, their true richness of species was often questioned by non-conservationists.
The Union Territory of Puducherry, particularly Karaikal district with its varied topography and climatic conditions constitutes vegetation of various kinds and there is a wide gap in information with regard to Phytodiversity in Karaikal District. The study area is an ideal site for study the diversity of plant resources of the coastal area, delta vegetation, mangroves and plain fertile ecosystems and agricultural lands.
According to the forest classification by Champion and Seth (1968), the vegetation of Karaikal district comprises of, a) Tidal swamp saline sediments along the estuaries and creeks, b) Plateau vegetation at plains representing moist to dry deciduous vegetation c) Some of the areas are also endowed with small grass and scrublands in the district. The present work is based mainly on the fresh materials collected by the authors from the district thoroughly through repeated field trips during the year 2009-2010.
The floristic composition of the district is remarkable in its diversity and luxuriance. In the present survey during second year, a total of 188 species under 152 genera and 61 families have been identified and recorded in the present work (Table-1). Dicotyledons are represented by 51 families, 106 genera and 130 species, while Monocotyledons are represented by 10 families, 46 genera and 58 species. The families have been arranged according to Bentham and Hooker’s classification.
Habit wise analysis of flora shows comparatively higher representation of herbaceous species 208 species (66.67%) were predominant followed by under-shrubs (9.94%), climbers (9.94%), shrubs (6.73%) and trees (4.80%). The prevalence of microclimatic conditions provided suitable habitats for herb-dominating flora. Of the 70 families, Poaceae is the most of dominant families with 32 species followed by Cyperaceae – 12, Euphorbiaceae – 11, Fabaceae 8, Mimosaceae – 8, Acanthaceae – 6, Asteraceae – 5, Bignonaceae – 5, Moraceae – 5, Apocynaceae – 4 and Malvaceae – 4. Most of the families represented in this flora are mainly tropical in distribution.
The 17 families represent one species each, i.e. Nelumbonaceae, Papaveraceae, Violaceae, Elatinaceae, Tiliaceae, Zygophyllaceae, Meliaceae, Anacardiaceae, Saxifragaceae, Rhizophoraceae, Barringtoniaceae, Passifloraceae, Apiaceae, Sphenocleaceae, Oleaceae, Gentianaceae, Lentibulariaceae, Pedaliaceae, Martyniaceae, Polygonaceae, Loranthaceae, Pontederiaceae, Moraceae, Ceratophyllaceae, Pandanaceae, Typhaceae and Aponogetonaceae. At genus level, Ficus showed the maximum diversity with 14 species followed by Cyperus (11), Cassia (9), Blumea (8), Bauhinia, Grewia, Hedyotis, Indigofera (each with 7 species), Acacia and Alysicarpus (each with 6 species). Analysis of flora shows that 48 % of total of genera (151) are represented by single species and a very few genera are represented by more number of species. Flowering and fruiting of the specimens were found peak in the month of February. In contrast, October yielded the smallest number of flowers and fruits. Out of 312 plants, 118 plant species occur in communes of the district.
As a functional group, aquatic macrophytes are of central important in the structuring of aquatic ecosystem in the district. Aquatic plants can provide food and shelter for other organisms that live in and close to the water, and also can provide spatial habitat complexity and refuge potential from predation for phytoplankton-grazing invertebrates, stabilize sediments and are intimately involved in nutrient cycling. However, the aquatic macrophytes and their communities have been among the most neglected components in the district. The floristic composition aquatic plants of the district is remarkable in its diversity.
The results of the present field study showed that a total of 59 species belonged to 49 genera in 30 families distributed in the District (Table-5). Among the aquatic plants, 10 species found in rare category i.e. Nelumbo nucifera, Bergia capensis, Dopatrium lobelioides, Limnophila polystachya, Hygrophila balsamica, Ceratophyllum demersum, Vallisneria natans, Monochoria vaginalis, Eleocharis acutangula and Schoenoplectus supinus subsp. Lateriflorus. Fourteen plant species considered as less-common distribution in the district. Remaining 35 aquatic plant species found in mostly all the aquatic habitats in the district
Cyperaceae is the most dominant families with 12 species followed by Poaceae (7), Onagraceae , Scrophulariaceae (3), Acanthaceae (3), Hydrocharitaceae (3), Nymphaeaceae (2) , Fabaceae (2) Convolvulaceae (2), Pontederiaceae (2), Araceae (2) and Lemnaceae (2). The proportion of aquatic plants are 19 % to total district flora. Most of the families represented in this flora are mainly tropical in distribution. Monocotyledon group with high frequency are important floristic aquatic elements in the district particularly Cyperaceae and Poaceae.
Local species composition is determined by the multi-factorial influence of historical, environmental and biological factors and is, therefore, a complex ecological question to evaluate. Aquatic plants species richness in the regions is hypothesized to have resulted from the presence of a complex mosaic of diverse habitats and steep ecological gradients. The existence of rivers, lakes and marshes form several aquatic biotopes including transitional zones, river beds, freshwater lakes, salt lakes, freshwater marshes, salt marsh, ponds and fields. Diverse of soils, rugged landscape, and variable rainfall patterns in the regions produce a mosaic of different habitats, which alone might support the higher species diversity.
Coastal region of Karaikal district is rich in biological resources and ecosystem diversity. The variety of natural resources such as foreshore sandy, inland sandy, salt marsh, estuaries, mangroves and maritime habitats were available in the district. Nagapattinam–Karaikal–Caddalore shelf of both Tamil Nadu and Puducherry was worst affected part of by the tsunami of December 2004 by tsunami surge and inundation of sea water. It has severe damage to coastal vegetation and soils turned into saline.
Sandy soil occurs along the mainland coast of the district. A little interior the sub coastal region has black and clay mixed sandy soils is present. It harbours good vegetation including mangrove species. The coastal and estuarine habitats have been under tremendous human induced stresses due to their immense economic, recreational and transport services. Increase in human population in estuarine areas will further increase the pressure on coastal plants. The population study helps us to understand the regeneration and recruitment patterns of different coastal species and, therefore, is an important conservation tool for sustainable management of natural resources. Assessment of the population status of mangroves is important from conservation point of view. The study area is constantly facing recurrent anthropogenic pressure in addition to cyclones and tsunami type disturbances.
Among the littoral species tolerating a certain amount of salinity in the soil are Exocaria agallocha, Clerodendrum inerme, Acanthus ilicifolius and Pandanus tectorius. Apart from these, herbaceous and greatly diversified flora is prevalent in the littoral zones of Karaikal district. The angiosperm flora of the Karaikal district has total of 157 species and they belong to 116 genera and 48 families. Poaceae and Fabaceae is the most dominant families with 16 and 15 species respectively, then followed by Cyperaceae (10), Convolvulaceae (8), Amaranthaceae (7), Solanaceae (6), Cucurbitaceae (6), Verbanaceae (5), Asteraceae (5) and Molluginaceae (5). Single species represented by 21 families in the coastal flora. The total coastal families contribute 154 species with proportion of 50% of the total district flora. Most of the families represented in this flora are mainly tropical in distribution.
Exotic species in the district
Alien species are non-native or exotic organisms that occur outside their natural adapted ranges and dispersal potential. The dispersion of plants from country to country may pave the way in highlighting the concept of exotics. The exotic plants are successfully establishing themselves in a new locality and contribute directly to biodiversity deterioration. Many alien species support our farming and forestry systems in a big way. However, some of the alien species become invasive when they are introduced deliberately or unintentionally outside their natural habitats into new areas where they express the capability to establish, invade and compete with native species which have elevated seed production and dispersal.
The present study listed out the existing exotic plants in the Karaikal district. The results of the present field study for exotic plants in the district showed that a total of 26 species belonged to 22 genera in 17 families distributed in the District (Table - ). Most of the exotic plants distributed in the district is the native of Tropical America and two plant species from African origin. Solanaceae is the dominant family with 4 exotic species followed by Asteraceae (3), Amaranthaceae (3 and Caesalpiniaceae (2).
Traditional medicine based on herbal remedies has always played a key role in the health systems of many countries. In India, the native people are exploiting a variety of herbals for effective curing of various ailments. The plant parts used, preparation, and administration of drugs vary from one place to other. However, the knowledge of herbal medicines is gradually perishing, although some of the traditional herbal men are still practicing the art of herbal healing effectively. These plants are frequently used by the local inhabitants of the area for treatment of various diseases. Ethno-medicinal studies have offered immense scope and opportunities for the development of new drugs. Some modern drugs have been deducted from folklore and traditional medicines. Living close to nature, traditional societies have acquired unique knowledge about the use of wild flora and fauna, most of which are unknown to the people who live away from such natural ecosystem as forests.
The present study found that medicinal plants recorded from the district are highly valuable for various medicinal uses. The study provides sufficient ground to believe that the traditional medicinal practice using native medicinal plants is alive well functioning in the study area. Many communities use wild plant parts for the primary healthcare, due to belief in its effectiveness. The treatment of disease with plants and plant products also causes little site effects and are cost effective too. Keeping the importance of plants in consideration, large numbers of commercially important medicinal plant species are over-exploited by persons involved in the trade. Lack of sustainable harvesting methods, inadequate knowledge about forest management and lack of financial resources are the main causes of over-exploitation, indiscriminate collection and over-exploitation of some commercially important species, and the populations of valuable species are decline.
During the preliminary survey, 20 species of rare medicinal plant species belonging to 20 genera and 14 families have been collected in this region. Fabaceae is the dominant family with 4 rare medicinal plant species followed by Malvaceae (3) and Euphorbiaceae (2). Notable rare medicinal plants, especially, Derris trifoliata, Mitragyna parvifolia, Grangea maderaspatana, Clerodendrum phlomidis, Sida spinosa, Phyllanthus rotundifolius, Cardiospermum canescens are recorded. These medicinal plants have healing and curing properties are well adapted themselves in this region.\
Based on the distribution of the taxa, some of the plant species are very rarely occur in the district. In the present survey, 33 plants were recorded in very low in number as well as in very small patches and most of them are shunted growth based on the habitat transition of this region.
E-flora of Karaikal district
In the correct format, biodiversity data from and local, regional and state level surveys could provide immensely valuable to the broader biodiversity community for various biological analyses for future planning. Although, taxonomically focused efforts are critical for repurposing natural history data for biodiversity analyses, there are some limitations to broader use by the diverse community of scientists and people who could benefit from the data. One impediment is that users must first accumulate the data on a local machine, in most cases taxon by taxon, and then convert the data into more usable formats for further analysis.