Biodiversity Status of the Immediate Vicinity of an Iron and Steel Recycling Factory in Ile-Ife , South-Western Nigeria

Floristic composition of vegetation communities of 27 plots established along a line transect in the four major directions was investigated in the vicinity of an Iron and Steel factory in Ile-Ife, Nigeria. The aim of the study was to document the plant species composition (biodiversity) of the plant communities found within the 350 m perimeter of the facility in the study area, which will serve as a reference data, as there was no reported study for the area prior to the establishment of the factory. Plant species were identified to species level in a 10 x 10 m plot and the occurrence of each species was described in semi-quantitative terms. The vegetation is heterogeneous in nature having 31 species of tree saplings and climbers, 26 of shrubs, 15 of herbaceous plants and 4 of grasses. These 107 plant species belong to forty six (46) plant families. The dominant families included Apocynaceae and Papilionaceae (9 species), Sapindaceae (8 species), Euphorbiaceae (6 species), Asteraceae, Cucurbitaceae, Malvaceae, Poaceae, Sterculiaceae and Verbenaceae (4 species). Among the diverse species recorded, Chromolaena odorata formed a ticket in almost all the plots. Other common species included Albizia zygia, Alchornea laxiflora, Aspilia africana, Cnestis ferruginea, Combretum sp., Icacina tricantha, Ipomoea involucrata, Momordica foetida, Panicum maximum, Paullinia pinnata, Simicrata welwitschii and Vigna gracilis. The index of similarity of the plots ranged from 6.1 to 71.8%. The potential and vulnerability of the species were highlighted. Adherence to and enforcement of environmental regulations was recommended for preservation of the native species.


Introduction
The floristic resource of any country plays a vital role in human development and survival.All living organisms depends on vegetation resources either directly or indirectly as they supply food, timber, fuel, shade, shelter, organic manure and conserve soil fertility (Tukur et al., 2013).The Nigerian floral resource and biodiversity has been under threat from unsustainable agricultural land use, urbanization, industrialization and from other anthropogenic factors (Obute and Osuji, 2002).This has formed the inclusion of vegetation studies in the Environmental Impact Assessment report for the establishment of major industries.This is done with a view to protect, manage and restore genetic resources for sustainable development despite the need for human development.Such studies does not only document occurrence of such species, but also usually provide measures of preservation of native species especially if rare.Vegetation studies are undertaken all over the world to document the notable floral diversity of the different localities.
Some researchers had carried out a lot of work to determine and document properties and uses of various indigenous plants in Nigeria.Bhat et al. (1990) documented the ethnobotanical survey of different plant resource in Kwara State of Nigeria.Nwosu (2002) also studied southern Nigeria pteridophytes, while Ibe and Nwufo (2005) reported the medicinal plants of the South-eastern Nigeria; Ubom (2010) gave the ethnobotanical biodiversity inventory of the plant resources in the Niger Delta area of Nigeria.Other studies of places that are potentially rich in plant species, but under threat due to urban development, are being studied.Soladoye et al. (2005) made an extensive study of the angiosperm community of the permanent site of Olabisi Onabanjo University with the aim of conserving them for posterity.Also, Durugbo et al. (2012) made a comprehensive vegetation inventory of the Redemption Camp (the headquarters of the Redeemed Christian Church of God) where the temporary site of its university is located, and emphasized some strategies for conservation.
The objective of this research was to document the floral component of the vicinity of the factory with a view to determining its floristic composition and similarity and to determine the state biodiversity erosion due to anthropogenic disturbances.

The study area
The study was conducted in Ile-Ife, Southwest Nigeria on latitude 7°29″ N and longitude 4°28″ E. It is located along Ife-Ibadan expressway about 4 km from Ife Central Local Government Secretariat and about 5 km from the Obafemi Awolowo University (OAU) main campus.Ile-Ife is situated within the rainforest zone and the climate is identified to be humid tropical climate characterized by two prominent seasons: the rainy and the dry season (Olajuyigbe et al., 2012).The dry season is short, usually lasting from November to March, and the longer rainy season prevails during the remaining months usually with two peaks, one in July and the other in September.The weather report from the meteorological stations located within OAU Teaching and Research farm showed the annual rainfall at Ile-Ife averaged 1400 mm yr-1 in a 5-year survey (Oke and Isichei, 1997) and mean annual temperature ranges from 28 to 34 °C (Olajuyigbe et al., 2012).

Sampling procedure
Data were collected from 27 sample plots of 10 x 10 m, laid along a line transect of 50 m distance from the fence of the steel recycling factory in order to capture, as close as possible, the native species of the factory location prior to establishment.The transects were laid along the four cardinal directions of North, East, South and West of the factory up to three hundred and fifty meters in each of the four directions.The total enumeration was done for two weeks between late January and early February (dry season).Within each sampling plot, the plants were identified to species level and the occurrences of the each species were recorded in each plot.Those that cannot be identified at the field were taken to IFE Herbarium for proper identification.Specimens of the plants species were collected from the study site and pressed.Identification, authentication and classification of the plant species into families was carried out in the Department of Botany Herbarium (IFE), Obafemi Awolowo University, Ile-Ife.
The occurrence of each species was described in semiquantitative terms in accordance with the method used by Edwin-Wosu and Edu (2013).Species with a wide frequency of distribution with many stands within a plot and across majority of plots are described as very abundant (++++).Some species with similarly wide frequency of distribution, but with few stands are said to be less frequent or abundant (+++), while species of limited geographical distribution and with a few stands are termed scarce (++) and very scarce (+) species.
The index of similarity (I.S.) of the 27 plots studied was calculated using the coefficient of similarity by Sorenson (1948): where C = the number of species common to the two plots compared; A = number of species in plot A; B = number of species in plot B.

Results and discussions
A total of 107 plant species belonging to 46 plant families were recorded in the floristic survey of the study area (Table 1) in which twenty one families were prevalently dominant, with two or more species.Among the dominant families, Apocynaceae and Papilionaceae had the highest species diversity in terms of richness with nine species.Other families recorded include Sapindaceae (8 species), Euphorbiaceae (6 species), Asteraceae, Cucurbitaceae, Malvaceae, Poaceae, Sterculiaceae, Verbenaceae (4 species), Combretaceae, Mimosaceae, Moraceae, Rubiaceae (3 species), Bignomiaceae, Caesalpiniaceae, Connaraceae, Convolvulaceae, Musaceae, Smilacaceae and Tiliaceae (2 species) respectively.The Nigeria rainforest belt is dominated by members of the families represented in the study area which agrees with the findings of Isichei (1995), Soladoye et al. (2005), Durugbo et al. (2012).In terms of species diversity, the study area recorded some variations in richness and evenness although Chromolaena odorata formed a ticket in almost all the plots.Other common species included Albizia zygia, Alchornea laxiflora, Aspilia africana, Cnestis ferruginea, Combretum sp., Icacina tricantha, Ipomoea involucrata, Momordica foetida, Panicum maximum, Paullinia pinnata, Simicrata welwitschii, Vigna gracilis and some cultivated Manihot esculenta (Table 2).The presence and dominance of Chromolaena odorata (an early colonizer of waste land), other early succession species and tree samplings indicate previous general disturbances (Hall and Okali, 1979).
In terms of habit and life form, there was a domination of trees and climbers with a representative total of 31 species each; twenty-six (26) were recorded as shrubs, fifteen (15) as herbs and four (4) of the grass family.The frequency and percentage of the life forms encountered in this study is presented in Table 3.The domination of trees (which were all saplings) and climbers, both representing 58% within the study area, is an indication of a regeneration process of secondary vegetation structure.
Hence, results showed that the vegetation in the area is more of a rich, diverse and heterogeneous nature with a mixture of various life forms involving trees, shrubs, herbs and climbers, characterized by both natural and anthropogenic influences.This is attributed to processes such as the influence of human activities (farming and constructions, soil removal), regeneration, as well as seasonal variation influenced by local environmental conditions (Edwin-Wosu and Edu, 2013).These had affected the vegetation structure in terms of species abundance and diversity.
This corroborates the affirmation of Offiong et al. (2012) that human activity is an important agent influencing plant species biodiversity.
The level of similarity was generally lower than 50% as observed in the standing vegetation of the plots using the similarity analysis.This is a reflection of the difference in species composition of the plots.Indices of similarity of each pair of plots are shown in Table 4.The highest variation (93.9) was observed between plot south 350 m and plot west 350 m, while the level of variation of 28.2 was the lowest, between south 100 m and south 200 m plots, possibly because of closeness of the two areas.
Out of the 46 families encountered in this study, 32 representing 70% had one or two species representation due to several anthropogenic activities.These activities portends grave danger to plant species losses occurring as a result of direct human activities (such as farming and soil collection for construction purposes) and fragmentation of the ecosystem from continued land development.This is because some of the plants species encountered in this study have been documented to have medicinal properties in the studies of Chima et al. (2013), Oni (2010).Some of these plants especially Panicum maximum, Sida acuta, Chromolaena odorata, Aspilia Africana, Andropogon gayanus have also been reported to be tolerant to metal pollution around metal based industries in the works of Anoliefo et al. (2008) and have been listed as candidates for potential phyto-remediation of heavy metal contaminated soils subject to further studies.
In view of the potential of the species identified in the study area and the fact that majority (70%) are vulnerable for elimination because of their limited number in representation and occurrence (having ≤ 2 species or occurring in ≤ 2 plots), government should enforce that the provisions of  Environmental Impact Assessment reports is strictly adhered to.These include among other things, compensatory planting and restocking of indigenous species, provision of new appropriate habitat and careful timing of major disturbances.

Conclusions
The findings of the present study provides a complete view of the floristic composition of the study area, which is rich in regenerating species that could result in the establishment of a diverse natural forest if protected to conserve the saplings of the regenerating species.However, since this previously forested area seems to have been opened up for development (potentially into industrial and residential estates), the importance of preserving the threatened diversity and available plant forms in the area cannot be overemphasized.Government, industries and individuals must abide by the provisions of the EIA act in further development of the vicinity.

Table 1 .
Species distribution according to families

Table 2 .
Occurrence and status of the plant species in the of study area

Table 3 .
The frequency and percentage of the plant life form of the study area