Effects of Industrial Activities on the Structure and Floristic Pattern of Vegetation within the Calabar Port Authority, South-Southern Nigeria

Effects of Industrial Activities on the Structure and Floristic Pattern of Vegetation within the Calabar Port Authority, South-Southern Nigeria
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Transcript Journal of Geography and Geology Vol. 4, No. 1; March 2012  Published by Canadian Center of Science and Education 203 Effects of Industrial Activities on the Structure and Floristic Pattern of Vegetation within the Calabar Port Authority, South-Southern Nigeria R. A. Offiong Dept. of Geog. & Reg. Planning, University of Calabar, Calabar, Nigeria   A. I. Iwara Dept. of Geography, University of Ibadan, Ibadan, Nigeria Tel: 234-803-945-1970 E-mail: G. N. Njar Dept. of Geog. & Reg. Planning, University of Calabar, Calabar, Nigeria   J. E. Atu   Dept. of Geog. & Reg. Planning, University of Calabar, Calabar, Nigeria   Received: September 5, 2011 Accepted: September 19, 2011 Published: March 1, 2012 doi:10.5539/jgg.v4n1p203 URL: Abstract The paper evaluated the effects of industrial activities on the structure and floristic pattern of woody tree/shrub species in the Calabar Port Authority. Three plots of 0.16 ha were employed to collect vegetation parameters (structure and floristic) from vegetation adjoining highly impacted site (HIS) and of less impacted site (LIS). Shannon-Wiener’s index showed that vegetation in the LIS was more diverse and heterogeneous than vegetation in the HIS with species diversity index of 2.29 and 2.26 respectively; whereas, the index of evenness revealed what tree/shrub species encountered at the HIS (0.53) were fairly equally abundant compared to tree/shrub species in the LIS (0.44). Vegetation in the LIS was richer at both spatial scale and taxonomic level than vegetation in the HIS, as a result of the favourable edaphic conditions and absence of toxic substances that facilitated vegetation growth. Therefore, to preserve the threatened diversity of available tree/shrub species in the area, government was encouraged to enact laws to stop the destruction and transformation of remaining hectare of vegetation into industrial and residential estates. Keywords:  Industrial activities, Calabar Port authority, Floristic composition, Structural composition, Adaptive capacity 1. Introduction Forest vegetation represents an important renewable natural resource with scientific, agricultural, medicinal,  pharmaceutical, educational, cultural and ecological values. However, irrespective of these immense ecological values of this species to biotic organisms especially man, anthropogenic activities such as deforestation,  pollution, industrialization, habitat destruction and degradation by physical and chemical means are causing significant and irreversible loss to this unique resource (El-Khouly, 2004). The landscape and vegetation of the Calabar Port environment have in the past three decades been subjected to irreversible environmental change, as a result urban and industrial development, agriculture, tourism, and population growth. The Calabar Port ecosystem contributes immensely to the economic development and environmental security of the state and country as a whole. It is noted to contain some virgin forest in the country with abundant resources (Lameed and Ayodele, 2008). The presence of industries and increasing urbanization in the area are immensely affecting the forest resources available. Indeed, the developmental efforts of the government and entrepreneurs in opening up Journal of Geography and Geology Vol. 4, No. 1; March 2012  ISSN 1916-9779 E-ISSN 1916-9787 204 areas for access to and fro the area have resulted in the removal of vegetation and subsequent degradation of the environment. The operations and effluent management of industries in the Calabar Port Authority in relation to other municipal wastes negatively impact on the wetlands, coastal and terrestrial ecosystem of the port environment. The industrial activity in the area includes food processing, fuel bunkering, tanneries, corrugated iron sheets, logging, shipping as well as municipal waste disposal. These activities result in soil pollution through the continuous discharge of untreated effluents, thereby increasing the levels of heavy metals in the soil. The concentration of heavy metals such as lead, oil and grease, copper, bromide, mercury, aluminum, zinc among others in large quantities induces many biochemical and structural changes in the biological systems of the plants (Kabir et al.,  2008), which inhibit plant growth. There is however urgent need to address the depletion of the area’s rich biodiversity to avoid inherent impacts (such as alteration in temperature, flood, accelerated soil erosion, soil loss etc) on the survival of man especially, the generations to come. Perhaps, the most serious risks of industrial production activities in the area include air and water pollution from the discharge of effluents (in  both gaseous, solid and liquid forms) without prior treatment into rivers, estuaries, lagoons, soil, vegetated areas and into the atmosphere. This of course is of great concern to the terrestrial and aquatic environment. The danger associated with these heavy metals on the environments stems from the fact that, they are not only toxic, but have cumulative or synergistic effects on terrestrial and aquatic resources when combined (Lameed and Ayodele, 2008; Muwanga and Barifaijo, 2006). Indeed, the continuous growth and expansion of industries in the Calabar Port environment is causing massive environmental pollution with inherent impacts on plants growth. Vegetation in the port authority differs one from location to the other depending on the extent of pollution. Polluted soil is noted (Kabir et al.,  2010) to alter  plant growth and quality, and the effects are often destructive. However, with the daily industrial activities and expansion of the work environments like the tank farm that is ongoing, the natural forest vegetation of the Calabar Port environment is drastically modified and altered resulting in structural and floristic changes, loss of habitat, and pollution of streams and disappearance of watersheds among others. Information on flora composition, diversity and biomass is absolutely essential in understanding forest ecosystem dynamics and conservation; as it may be a tool to estimate the level of adaptation to the environment and their ecological significance (Raddy et al.,  2008). However, for sustainable development, management and conservation of the remaining vegetation in the area in line with the global call for forest protection as sequester of CO 2 (carbon sink), it becomes imperative to evaluate the impacts industrial activities have on woody tree/shrub species in order to ascertain the ecological status of vegetation in the Calabar Port Authority and to call for its protection. This study is therefore relevant because it would contribute to the existing gap in knowledge; as there are paucity of documented studies that have examined this effect, despite the existence of the Calabar Port Authority for decades as a business hub of Cross River State. 2. Review of Related Literature The quest for man’s continued existence on planet earth has led to the modification of vegetation causing tremendous changes to the world ecosystems. Vegetation which helps to regulate the flow of numerous  biogeochemical cycles, most critically those of water, carbon, and nitrogen has been destroyed due to man’s desire to make living worthwhile (Iwara et al.,  2011). The need for the improvement in living standards such as industrial and residential expansion has led to the wanton destruction and pollution of forest vegetation. Pollution effects are indeed many and wide-ranging. There is no doubt that excessive levels of pollution are causing a lot of damage to biotic organisms including tropical rainforest. Several scholars have perhaps raised concern regarding the destruction of forest for various non-agricultural uses. For instance, Baskaran et al.,  (2009) assert that industrialization is an important tool for development of any nation, but they argue that industrial activity has expanded so much all over the world that today; it has become a matter of major concern in the deterioration of the environment. With the growth of industries (sugar, paper, tannery, textile, sago, dye industries), pollution of natural ecosystem by industrial waste water has increased tremendously. The effluents not only affect plant growth but also deteriorate soil properties, thereby hindering plant’s growth. Robin and David (2001) contend that the present levels of anthropogenic activities are rapidly altering natural habitat giving almost no time to local biota to develop adaptations. This results in irreversible variations in existing vegetal cover. They further argue that habitat destruction is the major cause of species extinctions. Seenivasan et al., (2008) note that industrial growth is causing an enormous environmental pollution. They note that industrial activities result in the pollution of soil; as polluted soil can alter plant growth and quality, and the effects are often destructive. Kabir et al.,  (2008) with similar view report that lead is a toxic environmental contaminant that induces many biochemical and structural changes in biological systems. McLaughlin et al., Journal of Geography and Geology Vol. 4, No. 1; March 2012  Published by Canadian Center of Science and Education 205 (1999) posit that heavy metal contamination of soils due to intensive industrial activities and agricultural development usually causes environmental problems. Elevated levels of heavy metals not only decrease soil microbial activity and crop production, but also threaten human health through the food chain. Dave and Krishnayya (2004) assert that species diversity varies greatly through space and time. Disturbance they argue is widely believed to be one of the main factors influencing variation in species diversity. Disturbance is a discrete event that abruptly destroys or displaces individual, by directly or indirectly changing the availability of substrate and /or other resources and creates an opportunity for new individuals to become established. In similar manner, Remegie and Yansheng (2008) submit that human disturbance like selective logging or cultivation seems to have an influence on plant species diversity. They contend that after disturbance, a habitant is more heterogeneous because of small, sunny gaps beside dense forest, different microclimate conditions in a near distance among others. These heterogeneous environments offer diverse possibilities for high amount of different species. Kitazawa and Ohsawa (2002) believe that various habitats can be regarded as spatially and temporally dynamic  patches of vegetation being subjected to diverse human interference. Kitazawa and Ohsawa allege that human activities can decimate or impoverish local and regional biota. Human they maintain have altered ecosystems to varying degrees and the resultant array of natural, semi-natural and human made ecosystems within a landscape can be conceived as constituting both a readily measurable gradient of land use and a more complex gradient of anthropogenic effects. Pitchairamu et al  ., (2008) in a study carried out to examine the floristic inventory and quantitative vegetation analysis of Tropical Dry Deciduous Forest in Piranmaali Forest, India discovered that tree species richness varies along the disturbance gradient in different stands. They reported that the undisturbed stand showed the highest species richness (11-9); species richness was lowest (5-4) in the disturbed stand, while in the moderately disturbed stand; the diversity was somewhat higher (8-7). They however concluded that tree species varied according to the disturbance gradient in different stands. Pickett and White (1985) assert that disturbance of an ecosystem means any discrete event that disrupts the ecosystem, community or population structure, or the physical environment. Species composition, community dynamic and ecosystem services of forest ecosystems become adversely affected by disturbances of both natural and anthropogenic srcin. They classified disturbance into large scale or community wide (landslides, volcanoes, drought, lightening, forest fire and various human activities) and small-scale disturbance such as mortality of few trees. The review of literature apparently reveals that industrial activities characterized by forest destruction and discharge of untreated wastes on the environment exert tremendous effects on the world’s ecosystems (terrestrial and aquatic). The indiscriminate discharge of untreated waste in whichever form on land increases the levels of heavy metals in the soil, which in the long-run leads to structural and floristic changes. The composition, diversity and structure of vegetation are important factors for assessing biological diversity of forest ecosystem because they give vital information on plants’ adaptation to changes in environmental conditions within or above their level of tolerance. 3. Materials and Methods   3.1 Study Area The study area was carried out within the work environment of Calabar Port Authority (NPA). The Calabar Port Authority lies between latitude 05 00’40”N and longitude 008 19’04”E (GPS readings). The area has temperature of 27 0 C, and rainfall ranges between 2000mm - 3000mm reaching its peak within the month of July and August; with a relative humidity of about 80%. It has a luxuriant topography which heads seaward; the soils are basically clayed-loamy. It also has luxuriant vegetation dominantly occupied by oil palms, grasses, herbs,  Alstonia boonei ,  Anthocleista vogelii , Terminelia spp, nypa palms and cultivated crops. The area is basically an industrial zone comprising of primary, secondary and tertiary industries. The industries in the area include food  processing industries, fuel bunkering activities, tanneries, metal works, building materials and engineering industries, logging activities, shipping services and financial institutions among others. These industries through their numerous production activities have impacted tremendously on the biophysical components of the Calabar Port ecosystem mostly soil and vegetation. The vegetation of the area has been seriously modified due to the continuous expansion of industrial units and the indiscriminate disposal of toxic substances. 3.2 Vegetation Sampling and Data Collection This study assessed the impact of industrial activities on the structure and floristic pattern of woody tree/shrub species within the Calabar Port Authority, by comparing vegetation parameters (structure and floristic) adjoining highly impacted area (Calabar Port Authority) with those of less impacted site (in Odukpani as control). The study sites have similar climate, but have different anthropogenic activities. The highly impacted site (HIS) Journal of Geography and Geology Vol. 4, No. 1; March 2012  ISSN 1916-9779 E-ISSN 1916-9787 206 (Calabar Port Authority) is completely an industrial estate with patches of farmlands, as such is mostly polluted  by the discharge of untreated industrial effluents, while the less impacted site (LIS) is characterized by fallows as a result of farming activities and sporadic logging as well as fuel wood harvesting activities. The vegetation of  both communities is purely fallow with patches of woodland. The heavy metal found in the highly impacted site includes caustic soda, dye, hydrocarbons, lead and fecal coliform. Two belt transects of 80m with interval of 5m in-between were laid in the two study sites. In each site, four quadrats measuring 40x40m were laid out of which three were randomly selected for estimating vegetation attributes. In all, six quadrats (three in the highly impacted site and three in the less impacted site) were selected and studied. However, in each quadrat, all woody stems ≥ 10 centimeters (cm) diameter at breast height (DBH 130cm from the ground) were counted regardless of trees or shrubs species. Other vegetation components examined in each quadrat were number of tree/shrub species, , tree height, crown and basal cover. Basal cover and crown cover were determined using the line transect method (Jennings et al  . 1999; Coulloudon et al. 1999); tree diameter was obtained using measurement at breast height of 130cm (Hall and Okali, 1979); tree height was measured using the trigonometry approach (in each quadrat, only tree species with the highest canopy was measured) (Offwell Woodland and Wildlife Trust, 2000). 3.3 Data Analysis The vegetation data were quantitatively analysed for species diversity, relative density, relative frequency, relative dominance, basal area, Importance Value Index (IVI) and species evenness. The Importance Value Index (used to determine dominance of tree/shrub species in the two vegetation communities) for the enumerated tree species was determined as the sum of the relative density, relative frequency and relative dominance. The various vegetation analytical methods employed are shown below: Basal Area (BA) for each plot was calculated using the formula given by Cintron and Novelii (1984); Adams et al.,  (2007) as: Basal Area (BA) = 0.7857 X D 2  (cm) Where: D = Diameter at breast height taken at 137cm Importance Value Index (IVI) for every species in each plot was calculated using the equation given by Cintron and Novelii (1984) and Adams et al. , (2007) as: IVI= Relative density (R  d ) + Relative frequency (R  f  ) +Relative dominance (R  D ) Where: d  No. of trees of species AR*100Total No. of all tree species    f  Frequency of occurrence of species AR*100Total frequency of all species    D BA of all trees of species AR*100Total BA of all species    Species Diversity Index for the two communities was calculated using Shannon-Wiener’s Index given by Price (1997) as: H 1  = S - Σ  Pi log e  Pi I=1 Where: H 1  = Shannon-Diversity Index; S = total no. of tree/shrub species in each community; Pi = the proportion or relative abundance of individual tree/shrub species; Log e  = Natural logarithm. Species Evenness Index for the two communities was calculated using Shannon-Wiener’s Index given also by Price (1997) as: E = H 1 / log e  S Where: E = Shannon-Wiener’s Evenness Index; H 1  = Shannon-Diversity Index for each study community; S = total no. of tree/shrub species in each community and Log e  = Natural logarithm. Journal of Geography and Geology Vol. 4, No. 1; March 2012  Published by Canadian Center of Science and Education 207 Test of significance : Independent T-test statistical technique was used to determine differences in tree growth variables (crown cover, basal cover, and tree size or DBH as well as tree height) between the two vegetation communities. The analysis was done using statistical package for social sciences (SPSS) 17.0 for Windows. 4. Results and Discussion 4.1 Floristic Composition of Woody Tree/Shrub Species In the highly impacted site (HIS), 67 woody stems of 11 tree/shrub species belonging to 9 families were encountered, while 191 woody stems of 14 tree/shrub species belonging to 12 families were recorded in the less impacted site (LIS) (Table 1). Mean stem density was 55 trees/shrubs per plot or 0.04 ha for vegetation in the LIS, while that for the HIS was 23 trees/shrubs ha -1 . The Vegetation in the LIS was more diverse, richer and heterogeneous at both spatial scale and taxonomic levels than vegetation in the HIS. This variation in the composition of woody tree/shrub species was attributed to the industrial activities prominent in vegetation adjoining NPA work environment which probably made it unfavourable for trees/shrubs to adapt to the area. The discharge of toxic substances inhibits the growth of tree/shrub species. Indeed, the retention and presence of toxic pollutants in the area greatly decreased the habitat potential of flora in the region. This result corroborates earlier studies like those of Uzair et al  . (2009) Kabir et al.  (2010) that the presence of toxic substances in the soil limits flora potential of the area. In the HIS,  Apocynaceae ,  Arecaceae and  Fabaceae were the most abundant families with 19, 19 and 9 tree/shrub species respectively; whereas, in the LIS, only  Fabaceae was the most abundant family with 26 tree/shrub species. The density of trees in the two vegetation communities differed significantly (t cal  = 11.085, t crit = 2.776). Also, results in table 1 showed that vegetation in the less impacted site was richer, more diverse and heterogeneous than vegetation in the highly impacted site with species diversity indices of 2.29 and 2.26 respectively. In addition, the index of evenness obtained for vegetation in the highly impacted site (0.53) revealed what tree/shrub species encountered along were fairly equally abundant compared to tree/shrub species in the less impacted site (0.44) that showed discernible pattern of dominance in occurrence and distribution by tree/shrub species like  Elaeis guineensis ,  Alstonia boonei,    Musanga cecropioides ,  Anthocleistra vogelii  and Terminelia superb . The presumably reason for the moderate species diversity obtained for vegetation in the highly impacted site could be that either that the impact of industrial disturbance was not enough to eradicate all the tree/shrub species from the area or that tree species might have survived the disturbance due to their adaptive capacity (Kuss, 1986; Adnan and Rashid, 2001). 4.2 Structural Composition of Woody Tree Species Information on the structure of vegetation in the study communities is shown in table 1. Total basal area for woody stems with ≥ 10 centimeters (cm) diameter at breast height measured for vegetation in LIS was 28016.72cm 2  with mean value of 9338.91cm 2 /ha, woody stems in the HIS was 4538.46 cm 2 with mean value of 1512.0 cm 2 /ha. However, the distribution of tree size across the 0.04 ha plots using DBH interval classes revealed the dominance of big stemmed individuals in the less impacted site (LIS), tree species increased with increasing girth (stem diameter) and girth class of 91 – 120cm recorded the highest number of individuals or stems of 86; while the girth interval classes for vegetation in the highly impacted site (HIS) was dominated by small stemmed individuals with girth class of 31 – 60cm having the highest number of stems (Figure 1). The low tree/shrub growth variables in terms of basal cover, crown cover, tree size (DBH) and tree height in the highly impacted site compared to those in the less impacted site was attributed to the varying site disturbances such as gravel deposition, farming activities and the discharged of toxic substances. These series of disturbances are reported (El-khouly, 2004; Kabir et al.,  2010) to have significant effects on the establishment and growth of  plants. The high structural distribution of vegetation parameters in the less impacted site was due to the relatively low level of disturbances, as the ecological status of the vegetation was near stable. Another possible reason according to Aweto (2001) is the favourable site condition like the abundance of sapling, facilitating ecological succession. The result of independent samples test showed that basal area and tree size varied significantly  between the two vegetation communities (t cal  = 12.00, t crit = 2.776 and t cal  = 14.623, t crit = 2.776). Tree distribution by height indicated that a total of 84.74m was measured across the 3 plots in the less impacted site with a mean value of 28.25m /ha (Table 1); the tallest tree/shrub species in the LIS were  Albizia zygia (35.12m),  Alstonia boonei  (27.08m) and  Musanga cecropioides  (22.54m); while in the highly impacted site, a total of 47.46m was measured across the 3 plots with a mean value of 15.82m /ha. The tallest tree/shrub species were Terminelia superb (18.96m),  Elaeis guineensis  (15.34m) and  Alstonia boonei  (13.16m). The height of trees in the two communities differed significantly (t cal  = 3.070, t crit = 2.776) with trees in the less impacted site showing better canopy structure. This structural characteristic was attributed to favourable site conditions like
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