VEGETATION STRUCTURE AND COM POSITION IN CORE AREA OF SARISKA NATIONAL PARK, RAJASTHAN ZAARA KIDWAI The Corbett Foundation, Village and P.O. Dhikuli, Ramnagar – 244715, India. Email: zaarakidwai@gmail.com ABSTRACT Species richness, diversity, basal cover and importance value index of the vegetation was analyzed in the Sariska National Park in the north-eastern part of Rajasthan from February to M ay 2009. Sixteen transects ranging from 1.8 to 2 km in length were laid throughout the 80 km² study area covering all the available habitat types. EstimateSWin750, PC- ORD, and TWINSPAN were used to calculate richness, diversity, and dominance of the region. The observed mean tree density (258.44/ ha) was lower than the mean shrub density (1178.74/ ha), though the diversity value was found to be higher for trees (46.47±0.53) compared to shrubs (8.0±0.02). M ajority of the intensive study area comprised of grasses (56.74%). Anogeissus pendula was found to be the most dominant species with GBH of individuals within class interval of mostly 40-50 cm and highest IVI value (44.01). Whereas for Acacia senegal the IVI value came out to be the lowest (8.98). Keywords : Density, Diversity, Dominance and Richness. Introduction structure and natural regeneration of trees in a dry deciduous forest in Nicaraguan and observed that these Tropical dry deciduous forest constitutes about forests are in process of biological degeneration and 38% of the total forest area in India (Dixit, 1997). Only a economic depletion. Apart from human induced few attempts have been made to evaluate the structure disturbances (Rai, 1985; Murphy and Lugo, 1986; Pauline of plant community of these forests (Singh and Misra, et al., 1996; Hare et al., 1997; Yadav and Gupta, 2006), 1978; Khan, 1996; Pauline et al., 1996; Dixit, 1997; natural disturbances such as hurricanes (Kelly et al., Parthasasrthy and Sethi, 1997). Tropical forest 1988), typhoon (Shibuya et al., 1997), salt sprays and ecosystems are one of the richest terrestrial ecosystems other coastal influences (Smith and Vankat, 1992; Hare et which support a variety of life forms and maintain huge al., 1997) have great impact on the species diversity of global biodiversity (Shi and Singh, 2002). Both structure dry deciduous forests. In view of the conservation of the and diversity of vegetation have strong functional role in rich biodiversity of this forest, it was declared as the controlling ecosystem processes like biomass Sariska Tiger Reserve by the government of India and the production, cycling of water and nutrients (Gower et al., Rajasthan state in 1979 (Yadav and Gupta, 2006). Thus, 1992). A strong correlation also exists between structural the present study aimed at evaluating the structure, diversity and species diversity (Sahu et al ., 2008). composition and diversity of vegetation in the tropical Previously, considerable amount of research has been dry deciduous forest of Sariska National Park that carried out regarding diversity index of tropical dry supports its diverse fauna. deciduous forest areas. Beard (1944); Lugo et al. (1978) and Murphy and Lugo (1986) also suggested that the Study Area number of species tends to increase along moisture The Sariska Tiger Reserve, spread over an area of 2 gradient in a semi-deciduous dry Guanica forest in Puerto 881 km , is located in the Aravalli Hills (79°17’-76 °34’E, Rico. M arod et al., (1999) reported low stem density and 27°05’-27°33’N). It is divisible into two distinct zones 2 basal area, and relatively high species diversity in the (Shahabuddin et al., 2006): the 274 km National Park 2 natural mixed deciduous forest in western Thailand, and and the 607 km Sanctuary. The climate is subtropical, attributed it to bamboo undergrowth and frequent fires characterised by distinct winter, summer, monsoon and which prevent continuous regeneration. post-monsoon seasons. Winter commences from The tropical dry deciduous thorn forests of November during which the temperature can be as low Rajasthan may be characterized as fragile ecosystems as 3° C, and average annual rainfall is 650 mm. The Sariska according to criteria given by Nilsson and Grelsson terrain is undulating to hilly in nature and there are (1995). Sabogal and Valerio (1998) evaluated the numerous narrow valleys (Sankar, 1994). The dominant Observed mean tree density (258.44/ ha) was lower than mean shrub density (1178.74/ ha) while diversity value was higher (46.47) for trees. Indian Forester, 139 (7) : 636-644, 2013 http://www.indianforester.co.in ISSN No. 0019-4816 (Print) ISSN No. 2321-094X (Online)