Introduction:

Documentation, conservation and finding enhancement strategies of biodiversity is considered to be one of the important challenges in present day conservation biology research and policy making process. Their importance is continuously being shown as they are found to be keystone for the sustainability of biosphere ( Swaminathan, M.S., 1992 ). Tropical evergreen forests are found to be most significant repository of such huge life forms across the globe, as these primary climax ecosystems show high endemism of flora and fauna and microbes, having unique structures, functions and relatively high productivity. Evergreen forest regions of India especially in Eastern Himalaya and Western Ghats are found to be huge biodiversity points as they are assigned one of the biodiversity hotspots at global scale ( Myers et. Al 2002 ). Western Ghats alone, for instance, has nearly 4800 species of flowering plants; nearly 2100 species among them are considered to be endemic ( Ramesh, B.R. & Pascal, J.P., 1996).

The ecological uniqueness of Western Ghats is the function of different factors namely, its origin, geological past, climate, impact of monsoon and anthropological activities and so on ( Radahakrishna, B.P., 1993 ). High species diversity seen here is, thus, also attributed diverse ecosystems evolved here like shola, grasslands, valleys, marshy lands, different forest ecosystems, riverbeds and banks, etc. Riparian ecosystem is one such vital component of Western Ghats , which has unique ecological characters.

Riparian zones of evergreen forest are the unique zones, where interface of water and land is seen. They are considered to be performing many vital functions like regulating water cycle of the forest floor, nutrient cycles of the lower command area, acting as breeding sites for many sensitive organisms, etc. These ecosystems are now being widely studied across the tropical region due to their increasingly evident significance ( Subramanian, K., 2005 , Jaffer et. Al ., 2002 and Maso-aki et al., 1997). Due to the unique physico-chemical and biological properties, they are found to be contributing much to the biodiversity of the Western Ghats too, especially the floristic diversity ( Pascal, J.P., 1986). This is a concept paper just to press for the need of bringing these issues to the larger domain of conservation biology. It is based on the experience of larger ongoing studies of Netravati river systems in central Western Ghats region in Karnataka. It tries to shed more light on the ecological uniqueness of these riparian zones with special reference to floristic compositions and their interaction, the different threats casting over these ecosystems and also some possible conservation strategies.

Materials & Methods:

Some aspects of taxonomy, ecology and conservation strategy of riparian flora are discussed here based on the field study done during 2004 –06 in Mundaje up stream zone of Netravati river valley in the foothills of central Western Ghats in Dakshina Kannada (12 0 29 ' 36 ” & 13 0 49 ' 22 ” N and 74 0 37 ' 24 ” & 75 0 41 ' 00 ” E).(Gazette of D.K.) These are the observations made as part of larger ongoing taxonomical and ecological investigations in the riparian zone of Netravati valley. The floristic study is done by laying six transects (100M X 5M) at each site for assessing tree species (Having dbh 10 cm or more). The species diversity, species abundance, relative dominance of species, population density, etc. are assessed. Ecological studies are done by physico-chemical analysis of water and soil samples from each study site in the riparian zone of this perennial river system in the evergreen forests at the foothills of Western Ghats . And some basic studies on anthropogenic pressure is also done in order to assess the threat status and to develop the conservation strategy for the same. Though, some taxonomical studies on the evergreen forest ecosystem of this region are done by earlier workers (Arora , R.K .1967), this is the first integrated taxonomical and ecological investigation done in these riparian zones.

Results:

The riparian zone of this perennial river system of Netravat i valley is found to be very much rich in terms of floristic diversity. More than 50 Angiosperm tree species and 12 shrub species are reported from this region. The most abundant tree and shrub species are listed in Table1. Several species like Cinnamomum ripaium and Ochlandr a species are found only in this ecological zone indicating the significance of these microhabitats. It seems that the reproductive biology of these species is very much linked to the dynamics of water in the stream and allied ecological functions. Therefore, the slope, water temperature, flow rate, etc. are assessed to construct the concrete characters of these riparian zones.

These riparian zones also show some unique ecological characters also. The floristic composition in the spray zone is found to be decisive in the functions like river bank stabilisation and landscape stabilisation of the adjacent regions. They also supply woody debris, organic matter, nutrients and also the shade to maintain the water temperature. Therefore, these dynamic forests and stream interactions are being further studied with special reverence to the evergreen forests of Western Ghats region.

Threat assessment to these ecosystems is also done by documenting the anthropogenic pressures. Several factors like encroachment, unsustainable harvest of minor forest products (MFP) like Cinnammomum , timber logging, extended cultivation, poor river bank management, etc. are found to be the major causes for the degradation of many spots in these zones. Apart from the biodiversity and ecological value, the conservation of these habitats is very much directly linked to the livelihood security of the people too. Studies elsewhere have shown that the destruction in the upper reaches of any river valley region in Western Ghats region could lead to severe water scarcity in the downstream. As the entire Dakshina Kannada population depends upon Netravati river for its water security, the conservation of the riparian zone in upper reaches is of immediate concern.

Therefore , there is an urgent need of developing conservation strategies for these fragile ecosystems, especially in these Western Ghats region. The forest department can come up with micro planning for all these habitats in association with civil society organisations and also the Biodiversity Committees of Grama Panchyatas . The Village Forest Committees (VFC) can also join for this purpose. The local academic institutions like schools and colleges can constantly monitor the status of the ecosystems by gathering data and regularly upgrading it.

Conclusions:

Riparian ecosystems form very unique ecosystems in the evergreen forest region of perennial rivers of Western Ghats . There is need of further carrying out wider studies and designing conservation strategies. In view of the increasing water scarcity in the coastal and central Deccan plateau in peninsular India , the conservation of riparian zones assumes high significance. The educational institutions need to take part in this conservation process of these unique aquatic regions by supplying regular feedback to the local management practices.

Reference:

1. Anonymous, 1973 . Gazette of India , South Kanara district of Karnataka.
2. Arora, R.K.1967 . The vegetation of South Kanara district, Western Ghats , Journal of Indian Botanical Society, Vol.46, pp15-24.
3. Jaffery, S., Welty Timothy Beechic, Kathleen Sullivan, David M. Huink, Roberts E. Bill, Chip Andrus, George Press , 2002. Riparian aquatic interaction simulator (RAIS): A model of riparian forest dynamics for the generation of large woody debris & shade, Forest Ecology& Management , 162, 299-318.
4. Myers, N., Mittermier R.A., Mittermeir C . G. Kent J, 2002. Biodiversity hotspots for conservation practices, Nature, 403, 853-857.
5. Pascal, J.P, 1986. Forest Ecology, Vol. II, Institute de Francis, Pondicherry .  
6. Radahakrishnan, B.P., 1993. Neogeo uplift & geomorphic rejuvenation of Indian peninsula, Current Science , Vol 64 (11&12) pp787-793.  
7. Ramesh B.R. & Pascal J.P., 1997. Atlas of endemics of Western Ghats , India . Institute de Francis, Pondicherry .  
8. Subramanian K., K.G. Shivaramkrishanan, & Madhava Gadgil , 2005. Impact of riparian land use on stream insects of Kudurmukh National Park , Karnataka, Indian Journal of Insect Science , 5: 49 .  
9. Swaminathan M.S. & Jana S.(Eds ) , 1992. Biodiversity: Implications for the global food security, Macmillan India Ltd., Chennai Indian,

Table 1. Check list of Angiosperm plant species with high occurrence in riparian zone of Mundaje stream in Netavati river Valley in central Western Ghats , Dakshina Kannada, Karnataka , India .

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