Woody Species Composition of Naturally Revegetated Coal Mine Spoils on Singrauli Coalfields, India

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1 Article International Journal of Environment and Bioenergy, 2014, 9(3): International Journal of Environment and Bioenergy Journal homepage: ISSN: Florida, USA Woody Species Composition of Naturally Revegetated Coal Mine Spoils on Singrauli Coalfields, India Arvind Singh Department of Botany, Banaras Hindu University, Varanasi , India Article history: Received 16 September 2014, Received in revised form 18 October 2014, Accepted 21 November 2014, Published 6 December Abstract: A study was conducted to explore the woody species composition of an age series of naturally revegetated coal mine spoils on Singrauli coalfields, India. The spoils chosen for the study were 2, 10 and 20 years old. Woody species composition increased with increasing age of the spoils and the number of woody species on 2 20 years old mine spoils varied between 2 and 31. Trees dominate over shrubs on the mine spoils. The total tree species density was greater on 20-years spoil as compared to 2- and 10-years old spoil. The two leguminous tree species Butea monosperma and Senegalia catechu have the greatest densities among all recorded woody species on 20-years old spoil, and were common to all the three age coal mine spoils. Most of the woody species colonizing the mine spoils were native and the constituent species of the tropical dry deciduous forest of the locality. Keywords: Coal mine spoil, Keystone species, Shrub species density, Singrauli coalfields, Tree species density 1. Introduction Open cast mining activity results in huge dumps of overburden material as mine spoil. Nutritionally and microbiologically impoverished mine spoils create inhospitable condition for plant

2 237 growth (Singh and Jha, 1993). Hence natural process of vegetation development on mine spoil is a slow process (Iverson and Wali, 1982; Jha and Singh, 1991, 1992, 1993). Initially the mine spoils are colonized by only a few species especially the grasses and legumes (Hazarika et al., 2006; Singh, 2006). The repeated growth of these herbaceous species adds organic matters and nutrients to the spoil subsequently paving way for woody species to colonize. Several studies have been conducted to explore the natural colonization of herbaceous and woody species with increasing age of coal mine spoils (Jha and Singh, 1991; Banerjee et al., 1996; Hazarika et al., 2006; Singh, 2006; Biswas et al., 2014). However, the main aim of the present study was to explore the woody species composition of naturally revegetated coal mine spoils with their advancing age in a dry tropical environment and also to identify the woody species suitable for revegetation of coal mine spoils on Singrauli coalfields. 2. Material and Methods 2.1. Site Description The study was conducted on the coal mine spoils of Singrauli Coalfields, India. The Coalfields of Singrauli extends over 2202 km 2 (latitude 23 o o N; longitude 81 o o 52 E and elevation m above msl) of which 80 km 2 lie in the state of Uttar Pradesh and rest in the state of Madhya Pradesh. The climate is dry tropical with temperature reaching up to 48 o C during month of June and lowering down to 5 o C in month of January. Rainfall varies from mm confined during monsoon months from June-September. The potential natural vegetation is tropical dry deciduous forest (Champion and Seth, 1968) Field Sampling Naturally revegetated coal mine spoils of 2, 10 and 20 years were selected for the study. For density measurement field sampling was done using 10, m quadrats randomly in month of September The woody species were listed and their numbers were counted in each quadrat. The density was calculated as total number of individuals of the species total number of quadrats studied (Misra, 1968). Sorensen s Similarity Index was used to compare the woody species composition between different ages of mine spoils (Magurran, 1988). 3. Results and Discussion A total of 31 woody species were recorded on three different age coal mine spoils of Singrauli coalfields (Table 1). On the youngest 2-year old coal mine spoil only 2 woody species were recorded and both of them were represented by trees while on 10-year old coal mine spoil 12 woody species

3 238 were recorded, of which 8 were represented by trees and 4 by shrubs. However, on 20- years old spoil 31 woody species were recorded of which 23 were represented by trees and 8 by shrubs. Thus the study clearly indicates that the woody species composition increased with advancing age of the coal mine spoils. This increase in species composition may be owing to increased fertility with increasing age of the spoil. With increase in spoil age coarse particles of soil decreases and fine particles as well as available nutrients in soil increases (Jha and Singh, 1990a). The study also reveals that greater number of trees and shrub species appeared on 10 and 20-years older spoils compared to 2-year old younger spoil. Other studies also suggest that number of trees and shrub species increases with increasing age of the coal mine spoils (Banerjee et al., 1996; Hazarika et al., 2006). In the study the two leguminous tree species, Butea monosperma and Senegalia catechu were common to all three age coal mine spoils suggesting that these two plant species have greater adaptability to thrive on harsh conditions offered by the coal mine spoils. The tree species density on 2-year old spoil varied between 20 and 40 ha -1 (total 60 ha -1 ) while the tree species density on 10-year old spoil varied between 20 and 100 ha -1 ( total 370 ha -1 ). The shrub species density on 10-year old spoil varied between 50 and 70 ha -1 (total 230 ha -1 ). On 20- years old coal mine spoil, the tree species density varied between 10 and 300 ha -1 (total 1570 ha -1 ) whereas the shrub species density varied between 50 and 120 ha -1 (total 640 ha -1 ). This result of the present study was in conformity to the finding that younger spoils have lower tree species density in comparison to older spoil (Hazarika et al., 2006). The study indicated that the total tree species density increased to 517% on 10-years old spoil and 2,517% on 20-years old coal mine spoil over the 2-years old spoil while the total tree species density increased to 324% on 20-years old coal mine spoil over 10-years old spoil. The total shrub species density increased to 178% on 20-years old spoil over 10- years old spoil. The study also indicated that the tree species density was the maximum on 20-year old spoil and the minimum on 2-year old spoil. Similarly the shrub species density was greater on 20-year old spoil than 10-year old spoil. Few woody species like Acacia auriculiformis, Leucaena leucocephala, Prosopis juliflora and Vachellia nilotica colonizing the 20-year old spoil are exotics. In fact these leguminous exotic species are frequently planted by Forest Department for revegetation of coal mine spoils on Singrauli coalfields (Singh et al., 1996; Singh, 2007). Hence the seeds from nearby planted trees may have been transported by some means to naturally revegetating coal mine spoils. Several woody species recorded in the present study on coal mine spoils like Anogeissus latifolia, Boswellia serrata, Butea monosperma, Cassia fistula, Diospyros melanoxylon, Grewia rothii, Haldina cordifolia, Holoptelea integrifolia, Lannea coromandelica, Madhuca longifolia, Melia azedarach, Nyctanthes arbor-tristis, Ougeinia oojeinensis, Senegalia catechu, Wrightia

4 239 antidysenterica, Woodfordia fruticosa, Ziziphus jujuba, Z. nummularia, Z. oenoplia and Z. xylopyrus are the constituent species of the tropical dry deciduous forest of the locality (Jha and Singh, 1992). Table 1. Woody species and their density (ha -1 ) on an age series of naturally revegetated coal mine spoils on Singrauli coalfields Sl. No. Woody species (Family) Habit Spoil age 2 yrs 10 yrs 20 yrs Density (ha -1 ) Density 1 Acacia auriculiformis A. Cunn. ex Benth. (Fabaceae) Tree Aegle marmelos (L.) Corr. (Rutaceae) Tree Anogeissus latifolia (Roxb. ex DC.) Wall ex Guill. & Perr. (Combretaceae) (ha -1 ) Density (ha -1 ) Tree Boswellia serrata Triana & Planch. (Burseraceae) Tree Butea monosperma (Lam.) Taub. (Fabaceae) Tree Calotropis gigantea (L.) W. T. Ait. (Apocyanaceae) Shrub Cassia fistula L. (Fabaceae) Tree Diospyros melanoxylon Roxb. (Ebenaceae) Tree Ficus benghalensis L. (Moraceae) Tree Ficus lacor Buch. Ham. (Moraceae) Tree Ficus racemosa L. (Moraceae) Tree Ficus religiosa L. (Moraceae) Tree Grewia rothii DC. (Malvaceae) Shrub Haldina cordifolia (Roxb.) Rids. (Rubiaceae) Tree Holoptelea integrifolia (Roxb.) Planch. ( Ulmaceae) Tree Lannea coromandelica (Houtt.) Merr. (Anacardiaceae) Tree Leucaena leucocephala (Lam.) de Wit (Fabaceae) Tree Madhuca longifolia (J. Konig) J. F. Macbr. (Sapotaceae) Tree Melia azedarach L. (Meliaceae) Tree Nyctanthes arbor-tristis L. (Nyctaginaceae) Shrub Ougeinia oojeinensis (Roxb.) Hochr. (Fabaceae) Tree Prosopis juliflora (Sw.) DC. (Fabaceae) Shrub Senegalia catechu (L. f.) P. J. H. Hurter & Mabb. (Fabaceae) Tree Syzygium cumini (L.) Skeels. (Myrtaceae) Tree Vachellia nilotica (L.) P. J. H. Hurter & Mabb. (Fabaceae) Tree Woodfordia fruticosa (L.) Kurz. (Lythraceae) Shrub Wrightia antidysenterica (L.) R. Br. (Apocyanaceae) Tree Ziziphus jujuba Mill. (Rhamnaceae) Tree Ziziphus nummularia (Burm. f.) Wt. & Arn. (Rhamnaceae) Shrub Ziziphus oenoplia (L.) Mill. (Rhamnaceae) Shrub Ziziphus xylopyrus (Retz.) Willd. (Rhamnaceae) Shrub

5 240 In the present study, Ficus benghalensis, F. lacor, F. racemosa and F. religiosa colonizing on 20- years old coal mine spoils are the ideal examples of keystone species. The similarity Index value reported for 10- and 20-year old spoil was much greater as compared to values reported for 2- and 10-year, and 2- and 20-year old spoil (Table 2). This clearly indicates that spoils with small age difference are much closer in terms of similar species composition than the spoils with big age difference. Table 2. Comparison of woody species composition between age series of coal mine spoils using Sorensen's Similarity Index Spoil age pair Similarity Index * 2 and 10 yrs and 20 yrs and 20 yrs Note: * Similarity Index (S): 2C/ (A+B), where C is number of woody species common to both the age series; A, the total number of woody species of one age series; and B, the total number of woody species of another age series. Of the total woody species recorded on coal mine spoils of different ages, the maximum number (8 species) were represented by Fabaceae family indicating that Fabaceae family dominates the woody species composition of naturally revegetated coal mine spoils on Singrauli coalfields. Several studies conducted to explore floristic composition reveal the dominance of Fabaceae family on mine spoils (Glenn-Lewin 1979; Jonescu 1979; Russell, 1985; Jha and Singh, 1990b; Singh, 2011). 4. Conclusions It can be concluded from the study that woody species composition increases with increasing age of the coal mine spoil. However, the natural colonization of woody species is quite slow. The leguminous Butea monosperma, Senegalia catchu and the non-leguminous Boswellia serrata, Nyctanthes arbor-tristis, Holoptelea integifolia and Grewia rothii are the most suitable native woody species for revegetation of coal mine spoils in a dry tropical environment of Singrauli coalfields. References Banerjee, S. K., Williams, A. J., Biswas, S. C., Manjhi, R. B., and Mishra, T. K. (1996). Dynamics of natural ecorestoration in coal mine overburden of dry deciduous zone of M. P., India. Ecol. Environ. Conserv., 2: Biswas, C. K., Mishra, S. P., and Mukherjee, A. (2014). Diversity and composition of vegetation on

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