Idea Transcript
Journal of Environmental Researh And Development
Vol. 1 No. 1, July-September 2006
SPECIES DIVERSITY AND DOMINANCE IN TROPICAL DRY DECIDUOUS FOREST ECOSYSTEM A.S. Thakur1 and P.K. Khare*2 1. Department of Botany, Govt. College, Khurai, Sagar-470117 (NDIA) 2. Department of Botany, Dr. H.S. Gour Vishwavidyalaya, Sagar-470003 (INDIA)
Received April 30, 2006
Accepted June 30, 2006
ABSTRACT Present study deals with plant species diversity and other parameters on vegetation analysis in ten forest stands of tropical dry deciduous forests around Sagar (Madhya Pradesh) Species diversity for all three vegetational components i.e. trees, shrubs and herbs were determined after Shannon and Wiener (1963). Diversity index ranged from 2.22 to 3.66 for trees, 1.26 to 1.86 for shrubs and 2.5 to 3.04 for herbs. Beta diversity indices ranged from 0.2 to 2.35 for all the sites studied. The values of concentration of dominance were generally low in all the communities indicating that the dominance was shared by more than one and/or many species. Dominance-diversity curves were prepared and similar patterns were found in all the sites. Log-normal curves were exhibited for trees and herbs whereas geometric curves were found in case of shrubs. Vegetation still posses comparatively higher species richness and diversity. It is experienced that vegetation in a state of stress due to biotic pressure and consequently being changing into xeric nature.
Key Words : Species diversity, Species richness, Dominance diversity curve, Tropical deciduous forest. INTRODUCTION Tropical dry forests form a major biome in India by covering around 38% of total forest area of the country. Central India hosts most of the tropical deciduous forests in Indian subcontinent. The structure and composition of deciduous forests change with the length of wet period, amount of rainfall, latitude, longitude and altitude. With a few exceptions ecological studies of tropical dry deciduous forest in India did not merit a greater attention. These forest
assume unusual significance for conservation since they are most used and threatened ecosystem especially in developing countries like India. The present paper deals with the study of species diversity and dominance in tropical dry deciduous forest ecosystem to provide current status of different forest communities, species richness and diversity in Sagar district of Madhya Pradesh. Sagar district occupying almost a central position in the country. Geographically it is
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Journal of Environmental Researh And Development
situated a few kilometers north of tropic of cancer between 23o10' to 24o27' North latitude and from 78o04' to 79o22' East longitude. The study was conducted selecting ten forest sites occurring in Sagar district namely Patharia, Mainpani, Jaruwakheda, Rahatgarh, Bahadurpur, Ramna, Ranipura, Gopalpura, Baraytha and Mohli. The forest of Sagar district can be classified under the tropical dry deciduous type after Champion (1936) and Champion and Seth (1968). MATERIAL AND METHODS Different ecological aspects of forest communities were analysed by selecting uniform stands at representative sties. Vegetational data collected following broad principles described by Misra (1968) and MuellerDombois and Ellenberg (1974). Species diversity was calculated by using Shannon and Wiener information index15. S
H (ni / N) log e (ni /N) i 1
Where, H = Shannon -Wiener index ni = Importance value of a species. N = Total importance value of all species. Beta diversity was calculated by the formula as given by Whittaker, (1965).
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BD = SC/ S Where, SC is the total number of species occurring in a set of samples counting each species only once whether or not it occur more than once and is the average number of species per individual sample. Concentration of dominance was calculated following Simpson's index16. Concentration of dominance (CD) = S
(ni / N)
Where, ni = Importance value of first species N = Total importance value of all species in a community. Dominance- diversity curves were drawn following Whittaker, (1965) and Ralhan et al (1982). RESULTS AND DISCUSSION Species richness represents the number of species available in a given area. Species richness ranged from 18 to 55 for trees, 5 to 10 for shrubs and 20 to 38 for herbs. More number of species in a community is ecologically important since diversity seems to increase as the community become more stable. Comparatively less number of species observed
Fig. 1: Dominance diversity curves for tree species of different sites of Sagar district. 2.5
I.V.I. (log)
2.0 1.5 1.0 0.5 0.0 Species sequence (1-n) Patharia
Mainpani
Jaruw akheda
Rahatgarh
Bahadurpur
Ram na
Ranipura
Gopalpura
Baraytha
Mohli
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2
i 1
Journal of Environmental Researh And Development
Vol. 1 No. 1, July-September 2006
Fig. 2: Dominance diversity curves for Shrub species of different sites of Sagar district. 2.5
I.V.I. (log)
2.0 1.5 1.0 0.5 0.0 Species sequence (1-n) Patharia
Mainpani
Jaruwakheda
Rahatgarh
Bahadurpur
Ramna
Ranipura
Gopalpura
Baraytha
Mohli
Fig. 3: Dominance diversity curves for herbaceous species of different sites of Sagar district. 2.5
I.V.I. (log)
2.0 1.5 1.0 0.5 0.0 Species sequence (1-n) Patharia
Mainpani
Jaruw ak heda
Rahatgarh
Bahadurpur
Ram na
Ranipura
Gopalpura
Baraytha
Mohli
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Table 1: Richness, dominance and diversities of tree, shrubs and herbs at different study sites.
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Journal of Environmental Researh And Development
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diversity curves (Fig. 1 and 3) indicative of shared resources pattern by a number of species and mixed nature of vegetation. On the contrary, shrub layers showed geometric series of dominance diversity curves showing low diversity and less sharing of resources (Fig. 2). It has been observed that there is a great reduction in species richness of shrubs when compared to reports of Misra and Joshi (1952) and Bhatia (1955). This decrease may be explained on account of increasing grazing and cutting pressure which indices the dominance of xerophytic species such as Lantana camara and Carissa spinarum and disappearance of species less adapted to dry conditions and intense biotic influences. The situation further explains the spread of Lantana camara throughout this region since its invasion due to its competitive ability over other species of shrubs.
in the present study may be attributed to species confined only to the sampling area. Result pertaining to species diversity showed highest diversity index of trees (3.66) and herbs (3.04) at Baraytha. On the other hand comparatively less, however maximum diversity index (1.86) was observed for shrubs at Ramna. Considering the vegetation of whole district, species diversity ranged from 1.26 to 3.66 (Table 1). The Shannon - Wiener's diversity index ( H ) showed that it was much higher at three study site i.e. at Patharia. Baraytha and Mohli, as compared to other. They are comparable to those reported for tropical wet evergreen forests of southern western ghats (Parthasarthy & Karthikeyan, 1997). Others can be compared to tropical dry evergreen forest ( H = 2.28) of South India9. Species diversity indices are more or less similar (2.1 to 3.83) to those reported by Watve et al. (2003) for semi evergreen forest fragments of northern western ghats. However, Pascal (1988) reported much higher Shannon Weiner's Index (4.3) for west evergreen forest of the western ghats. It is evident from the results that in general species diversity of tropical dry deciduous forests is much lower however, at places it may be higher due to more physical heterogeniety as in the present study. Results indicate that the vegetation still posses comparatively higher species diversity even after under continuous biotic influences. It may be attributed to greater heterogeniety of the physical condition and a greater potential of regeneration and hardiness of the species. Results of Beta diversity indicates that the communities were having beta diversity index from 0.2 to 2.35, a low index values as compared to those reported by others for communities occurring in different environmental gradients.1,2 The values of concentration of dominance were generally low in all the communities studied indicating that dominance was shared by more than one and/ or many species (Table 1). At all the sites trees and herbs communities showed log-normal dominance
CONCLUSION It is experienced that vegetation in a stress of biotic pressure gradually transform into xeric nature. Interestingly most of the species are still retained due to their broad ecological amplitude and greater adaptability against biotic influences. They are having a good potential for natural regeneration. The vegetation can be easily conserved for its diversity and growth by adopting the strategy of reduction of biotic pressure. 1.
2.
3. 4.
5.
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12. Ralhan P.K., Saxena A.K. and Singh J.S., Proc Indian Nat. Sci. Acad. 848, 121137 (1982). 13. Rawat R.S., Indian Journal of Forestry 24(4), 419-426 (2001). 14. Rikhari H.C., Chandra R. and Singh S.P. Proceeding Indian National Science Academy, 55: 431-438 (1989). 15. Shannon C.E. and Wiener W., The Mathematical theory of communication. University of Juionis Press, Urbana. 117 (1963). 16. Simpson E.H., Nature, 163, 688 (1949). 17. Watve A., Gandhe R.V. and Gandhe K.R., Ann. For., 11(2): 155-165 (2003). 18. Whittake R.H., Science, 147, 250-260 (1965).
Misra R., Ecology Work Book. Oxford and IBH Publishing co, New Delhi. 235 (1968). 7. Misra R. and Joshi N.K., J. Indian Bot. Soc., 31, 154-170 (1952). 8. Mueller-Dombois D and Ellenberg H., Aims and methods of Vegetation Ecology : John Wiley and Sons, New York, 525 (1974). 9. Parthasarathy N. and Sethi P., Trop. Ecol. 38 (1), 19-30 (1997). 10. Parthasarathy N and Karthikeyan, R., Trop. Ecol., 38, 297-306 (1997). 11. Pascal J.P., West evergreen forests of the Western Ghats of India: Ecology, Structure, floristic composition and succession. Int. Francais de Pondichery, traw. De la Sci. et Tech. Tome XX bis, 345 (1988). 6.
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