ABSTRACT
The study described the composition and status of undergrowth (shrubs, herbs and grasses) in a degraded deforested area of Chittagong (South) forest division, Chittagong, Bangladesh. A stratified random quadrat method was used in the study. The area on the whole consists of 45 species of undergrowth of 31 families. Shrubs layer includes 14 species of 12 families and herbs and grasses include 31 species of 19 families. Among the shrubs Clerodendrum viscosum shows the highest density (94 plants/100 m2) and Cassia alata shows the lowest density (8 plants/100 m2). The highest frequency was found in Clerodendrum viscusum (50%) and lowest frequency was found in Corcorus capsularis (5%). The highest abundance was recorded in Corcorus capsularis (13) followed by Ipomoea fistulosa (11) and Lantana camara (11). Among the herbs and grasses Imperata cylindrica shows the highest density, frequency and abundance (7638 plants/100 m2, 77% and 394, respectively) followed by Cynodon dactylon (687 plants/100 m2), Unidentified4 (265 plants/100 m2). The lowest frequency (5%) and abundance (3) were recorded in Pueraria sp. and Musa paradisiaca, respectively. Abundance frequency ratio of each shrubs, herbs and grasses are >0.05 showing the contagious nature of each species distribution.
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DOI: 10.3923/ajps.2004.651.654
URL: https://scialert.net/abstract/?doi=ajps.2004.651.654
INTRODUCTION
Biodiversity is a concept, which refers to the range of variation or differences among some set of entities within the living world[1]. Biodiversity or biological diversity pertains to the diversity of biological organisms, both animals and plants in a region, country; continent or the world[2]. Total forest area of Bangladesh is 1,334 000 ha of which natural forest is about 709000 ha and plantation is about 625000 ha. From 1990-2000, 7% natural forest is reduced and 4% plantation is increased[3]. Bangladesh has a rich biological heritage of flowering plants. An estimated 5000 species of angiosperms alone are available in the forest of Bangladesh of which 2260 species are reported from Chittagong[4]. In 1990s only 3.7% Tropical forest protection has been provided in Bangladesh and 12 tree species were threatened[3]. A large portion of diversity already lost due to the multidimensional (e.g. illicit felling, natural calamities etc.) problem facing the forest of Bangladesh. After the Convention of Biological Diversity Government of Bangladesh has taken a strategy to conserve the biological diversity of the country by providing adequate protection.
The study site was once a natural forest and then cleared for plantation of Tectona grandis and Eucalyptus camaldulensis. However the area was completely illicit felled. Now regeneration of felled trees from coppice and natural regeneration of some other native species were started with some undergrowth[5]. Evaluation of biological diversity from conservation point of view in disturbed areas focuses on measuring riches and not more complex indices of heterogeneity[6]. More frequently the number of species in certain taxa and vegetation types are measured but occasionally abiotic features are used[7]. Much of the biodiversity in tropical forests resides in herbs, shrubs and small trees[8]. No published information on the species composition and diversity in the shrubs, herbs and grasses in the study area is available. Therefore a need exist to identify the undergrowth and assess their diversity. Present study was conducted to determine the composition and status of undergrowth in the study area.
MATERIALS AND METHODS
Study site: The study was conducted in the degraded deforested area of Bamerchara and Danerchara at Sheelkup union of Banskhali upazilla of Chittagong, Bangladesh. It lies between 21°51 to 22°11 N latitude and 91°51 to 92°03 E longitude[9]. It is a reserved forest under Jaldi beat of Jaldi range of Chittagong (south) forest division[10]. Government has declared it as a biodiversity conservation area and some protection has been provided in the area. Both the lakes are connected with a narrow channel and surrounded with small hills. The climate is typically sub tropical with a long dry season extending from October to May. From June to September the southwest monsoons provide the majority of the average rainfall of about 2540 mm, average temperature vary from 39.4 to 8.3°C throughout the year, the humidity is very high throughout the year[9].
Methods: Stratified random sampling was used in the study. Thirty sample plots were selected at Danerchara and 10 sample plots were selected at Bamerchara proportionally on the map and finally identified in the field. Sample size 2x2 m was selected using species area curve[11]. All the species and individuals of shrubs and herbs and grasses in the plot are counted. Herbarium of each species was prepared from representative sample. The collected specimens were identified following[12,13] and taxonomists of Bangladesh Forest Research Institute, Chittagong. Density, frequency and abundance, were calculated following[14,15]. Abundance frequency ratio (A/F) was calculated according to Curtis and Cottam[16] (<0.025-regular, 0.025 to 0.05-random, >0.05-contagious distribution). Data was collected during February 2003 to August 2003.
RESULTS
Species composition: Shrubs layer consists of 14 species of 12 families. Family Caesalpiniaceae and Verbinaceae dominate containing 2 species each and remaining family contains 1 species each (Table 1). Thirty one species of herbs and grasses of 19 families are recorded in the study area (Table 2). However, 3 species of Graminnae family and 2 species of Rubiaceae family were unidentified. Graminnae family is dominated containing 8 species followed by Polygonnaceae (3 species) Convolvulaceae and Rubiaceae (2 species each). The remaining family contains 1 species each.
Density, frequency, abundance and abundance frequency ratio: Among the shrubs Clerodendrum viscosum shows the highest density (94 plants/100 m2) followed by Eupatorium odoratum (86 plants/100 m2), Ipomoea fistulosa (74 plants/100 m2) and lowest density was found at Cassia alata (8 plants/100 m2). The highest frequency was found in Clerodendrum viscosum (50%) followed by Eupatorium odoratum (47.5%) and lowest frequency was found in Corcorus capsularis (5%). The highest abundance was recorded in Corcorus capsularis (13), followed by Ipomoea fistulosa (11), Lantana camara (11) and Urena lobata (8). The lowest abundance was found in Cassia alata (3) (Table 3).
Table 1: | Shrub species of the study area with their species and family name |
Table 2: | Herbs and grasses of the study area with their species and family name |
Each species of shrubs shows the abundance frequency ratio of > 0.05 which indicate the contagious distribution of each species. Table 4 shows the density, frequency, abundance and abundance frequency ratio of herbs and grasses in the study area. Imperata cylindrica shows the highest density (7638 plants/100 m2) followed by Cynodon dactylon (687 plants/100 m2), Unidentified4 (265 plants/100 m2) and Mimosa pudica (233 plants/100 m2). Pueraria sp. shows the lowest density (5 plants/100m2) and remaining species shows the density less than 120 plants/100 m2 each in the study area.
Table 3: | Density, frequency, abundance and abundance frequency ratio (A/F) of shrubs in the study area |
Table 4: | Density, frequency, abundance and abundance frequency ratio (A/F) of herbs and grasses in the study area. |
Imperata cylindrica shows the highest frequency (77%) followed by Mimosa pudica (75%) Cynodon dactylon (27%), Mikania cordata (25%), Polygonum barbatum, unidentified-3 and Convolvulus sp. (22% each). Pueraria sp. shows the lowest frequency (5%) among the herbs and grasses in the study area. Abundance was highest in Imperata cylindrica (394), followed by Cynodon dactylon (100), Unidentified-4 (53). The lowest abundance was found in Musa paradisiaca (3.29). Abundance frequency ratio of each herbs and grasses are >0.05 showing the contagious nature of each species.
DISCUSSION
Under the plantation of Anogeissus pendula and Hollarhina antidysenterica sixteen and twelve species of ground flora were recorded, respectively[17]. Chowdhury et al.[18] recorded 114 species of undergrowth of Tectona grandis plantation at Ichamati forest beat of Chittagong, Bangladesh. The species composition of the area is very poor (Table 1 and 2). The area is dominated by Tectona grandis and Eucalyptus camaldulensis. Insufficient undergrowth of Tectona grandis plantation was due to broaden leaf canopy, microclimate and site topography[19]. These research findings may be true for the study site also. It is a degraded site and requirement of species started recently due to some protection by the Government. So it could be enriched its species composition of undergrowth in the future if the providing protection will be accessible. Considering density, frequency and abundance the area is dominated by Corcorus capsularis, Ipomoea fistulosa and Lantana camara though density of Clerodendrum viscusum, Eupatorium odoratum and Ipomoea fistulosa are more and Eupatorium odoratum, Aralia sp. and Ipomoea fistulosa are frequently distributed in the shrubs layer (Table 3). Imperata cylindrica and Cynodon dactylon are dominated, denser and frequently distributed in the herbs and grasses layer of the study area (Table 4). The area was a natural forest and plantation of Tectona grandis and Eucalyptus camaldulensis were clearly illicit felled and was barren for sometimes. Then Imperata cylindrica and Cynodon dactylon covered the area. Contagious pattern illustrate a nature of natural vegetation[17,20]. From abundance frequency ratio (A/F) of shrubs, herbs and grasses it is very obvious that the area again turning to a natural vegetation. Researches conducted in a number of tropical countries have shown that tree planting on a degraded tropical land can dramatically increase the native forest species diversity. Under appropriate conditions these plantations seem to catalyze natural forest succession by modifying understory microclimate conditions and soils, thereby creating a more favourable environment for the establishment of native forest flora and also for attracting seed dispersing wildlife which lead to the progressive enrichment of biological diversity[17]. The coppice of Tectona grandis and Eucalyptus camaldulensis might act as a facilitator of the regeneration of shrubs and herbs from a completely barren to a condition of conservation. Therefore, a proper protection from illicit felling of coppice and scientific management of undergrowth may lead the area as a biodiversity rich site in the country.
REFERENCES
- Chowdhury, M.A.M., M.K. Hossain, T.K. Osman and M.A. Gafur, 1985. Studies on the undergrowth of Teak Tectona grandis at Ichamati Forest beat, Chittagong. III. Relations between soil properties and dominants undergrowths. Chittagong Univ. Stud. Part II: Sci., 9: 42-49.
Direct Link - Margules, C. and M.B. Usher, 1981. Criteria Used in Assessing Wildlife Conservation Potential: A Review Biology Conservation. In: Biological Diversity in Surface Mined Areas After Reclamation, Soni, P., H.B. Vasistha and O. Kumar (Eds.). Vol. 115, Indian Institute of Forest Management, India, pp: 475-482.
Saheduzzaman Reply
Very good topics for discussion and restoration of the ecosystems.