The Sundarbans is the world’s single largest mangrove forest. That extends across Bangladesh and Indian state of West Bengal. It is formed by the interplay of greater Ganga–Brahamputra estuarine system that supports brakish water environment. 62% area of the total Sundarbans is situated in Bangladesh and the rest 38%is in West Bengal. The forest is estimated to be five thousand three hundred years old and is unique reservoir of bio-diversity (Chowdhury 2001). Mangroves are the threatened coastal, deltaic intertidal halophytic plants, play very dominant and important roles in the estuarine mouths, sea land interphase areas or deltaic ecosystems of both the tropical and subtropical zones, especially, in the highly populated South East Asian countries, several PacificIslands and Australian coasts. In spite of their important role and immense ecological impacts these mangroves and the mangrove ecosystems have faced both biotic and abiotic threat and these highly productive mangrove zones have been cleared or the mangrove ecosystems have also been degraded very rapidly during the last three centuries (Naskar et al. 1999).
Sundarban River Side
The forest Sundarbans is flat and its elevation is hardly three meters above mean sea level (Siddiqui 2001). The entire area is intersected by a complex network of streams and rivers varying considerably in width and depth (Choudhury 1968). At a comparatively recent period, all these rivers were connected with the Ganges. Now however, the only one which is a direct influence is the Baleswar which is responsible for fresh water supply in the eastern part of the Sundarbans. A number of the rivers namely Passur, Sipsah, Arpangasia, Malancha and to a slight extent the Jamuna and the Rainmangal have indirect connection and they receive overflow of the Ganges during rains. They also receive a considerable amount of local drainage throughout their long and meandering courses during the monsoon (Siddiqui 2001). Erosion and compensatory accretion are occurring continually along the banks of all larger rivers, but the rivers of the Sundarbans, are more stable than the main streams of the Ganges and the Brahamaputtra further east (Das and Siddiqui 1985). The floristic composition of the Sundarbans is rich compared to many other mangroves of the world (Choudhury 2001). Prain (1903a) recorded 334 species of plants belonging to 245 genera and 75 families for the Sundarbans and adjoining areas. Henning (1892) reported 70 species from 34 families for the entire Sundarbans (Indian and Bangladesh). Chaffey and Sandom (1985) presented a list of 66 species in the Bangladesh Sundarbans from 37 families.
Sundarban Sundari Tree
Heritierafomes (Sundri) and Excoecaria agallocha (Genwa)are the principal species of this forest.H.fomes constitutes about 65% of the total merchanttable timber. (i) H.fomes (Sundri), (ii) H.fomes (Sundri), – E.agallocha(Genwa), (iii) E.agallocha (Genwa) – H. fomes (Sundri), and (iv) Ceriops decandra (Goran) – E. agallocha (Genwa) forest typc caovered 21%, 29.7%, 14.8% and 14.46% of area respectively (Siddiqui 2001). Other more important tree species include Xylocarpus mekongensis (Passur), Avecennia officinalis (Baen), Amoora cuculata (Amur), Xylocarpus granatum (Dhundul), Sonneratia apetala (Keora), Rhizophora mucoronata (Garjan), Bruguieragymnorrhiza (Kankra), Ageiceras corniculatum (Khalshi) (Rahman 1995).
Sundarban's Fisherman Casing Fish
The Sundarbans is an important natural resource that provides a large number of products such as timber, pulpwood, fish, thatching materials, honey, bees wax shells etc. In addition it supports a very rich and diverse flora and fauna. It is the largest remaining habitat for the Royal Bengal Tiger. Some 600,000 people are directly dependent on this forest for their livelihood. In addition, the mangrove forest acts as a natural barrier to cyclones and tidal bores, and protects the densely populated agricultural areas to its north. The Sundarbans and the coastal plantations are important food source and breeding ground for off-shore fisheries, economic and commercial shrimp cultivation particularly in the south western districts of Bangladesh (Rahman 1995).
Mangroves, the sole vegetation of this area, constitute a very specialized forest ecosystem at the lands sea interface of the estuarine region in the tropical and subtropical countries. One of the important features of this area is the regular flooding by tidal water twice daily. The tidal water passing through the creeks, crevices inundate the lower part of the vegetation. This is a very dynamic ecosystem provide a unique opportunity for the interactions among plants, soil, adjoining water and aquatic living resource, for example-prawns, fishes and other biotic organisms and help to exchange different chemical indices and energy contents among themselves (Nanda 1999).
The freshwater flow from the upstream of the river Ganga is now reduced in comparison to the early 20th century; consequently the deltic lands in this lower Ganga basin of the Sundarbans tidal forests are now almost disconnected from many of these distributaries of the river Ganga. The reduced flow from the up stream has turned the tidal river water more saline, hampering the natural regeneration process of many important mangrove floras. Now-a-days, there is an alarmingly in creased population pressure on the natural virgin mangrove forests, severely affecting the regeneration process. Both the biotic and abiotic factors in this Sundarbans mangrove forest affected the natural growth and developmental process of mangrove flora (Naskar and Guha 1986).
Rayel Bengal Tihger of Sundarban
Although mangrove ecosystems have tremendous value for coastal communities and associated species, they are being destroyed at alarming rates (Shamsuddoha et al. 2007). Over at last 50 years, about one third of the world’s mangrove forests have been lost (Shamsuddoha et al. 2007). Human threats to mangroves include the overexploitation of forest resources by local communities, conversion into large scale development such as agriculture, fishery, salt extraction, urban development and infrastructure, and diversion of fresh water for irrigation (UNEP 1994). Mangrove flora is very specific for their salt tolerance habitats, tidal inundation, and salt elimination nature. Any changed soil and water conditions have severe effect on these mangrove flora and fauna. But unfortunately, the physiognomic features of the Sundarbans are very much interfered by human activities and mangrove forests are gradually getting eliminated from these areas (Naskar 1996).
Mangrove Forest of Sundarban
The greatest human treat to mangroves is the establishment of shrimp culture ponds. Because mangroves are often viewed as wastelands, many developing countries are replacing these forests with agricultural land and/or shrimp culture production. Shrimp culture pond accounts for the loss of 20 to 50 percent of mangroves worldwide (Primavera1997).Since all human society depend directly or indirectly on their ability to manage plants, animal and micro-organism effectively, the task of sustainablemanagement of mangrove forest ecosystem is of paramount importance. According to Raven (1988) the most of world’s tropical forests will be destroyed or severely damaged within next 25 years, because of the explosive growth of human population in the tropics and subtropics, extensive and acute poverty in the region, and above all, collective ignorance of effective ways to manage tropical ecosystems so that they will be productive on a sustainable basis.
International awareness focused on preserving biodiversity for immediate use for the future has gained momentum only in recent years (UNCED 1992). Genetic resources are a common heritage to mankind; they should be made available to promote development in present generations while, at the same time, their availability for the benefit of future generations must be assured. Bangladesh is unique in having diversified genetic resources in a range of habitats. The term genetic resources relates to actually or potentially useful characteristics (disease resistance, rapid growth, yield of quality factor or the presence or absence of chemical etc) of plants and animals those are transmitted genetically (FAO,1984). The main causes of resource depletion include degradation of natural forests, due to a combination of activities like urbanization, deforestation, jhooming, or intentional firing, improper land use and commercial logging, felling etc. At the beginning of the eighteenth century the forests are about double of the present conditions.
Sundri Tree's Root in Sundarban
The Bangladesh Sundarbans lies between the latitudes 21o 31` and 220 30` N and between the longitudes 890 and 900 E. It occupies a land of 401,600 ha, of which 395,500 ha are covered by forests (Chaffey et al. 1985), and comprises 44% of the total productive forest of Bangladesh (Anon 1989). Of the total area, approximately 70% are lands and 30% are waters. The distance between the northern and the southern boundaries averages about 80 km, although the distance between the extremities is about 100 km. The east to west distance within Bangladesh is about 80 km. The Sundarbans is bound by heavily populated agricultural land on the north and east, and by the Indian Sundarbans on the west. The Bangladesh Sundarsbans is a ReservedForest and has been divided into four administrative Ranges with 55 Compartments. During the British period, i. e., before 1947, the entire Sundarbans was administered as a single Forest Management Division (Siddiqui 2001). Satkhira range is under Satkhira district is the South West region of Bangladesh. This area is polyhaline zone represents the western part of the Aura Sipsa and east of the Raimangal and is connected with the upper moribund part of the kobadak-Betna river system. The subsystem has its lost connection with the Ganges and does not receive any surface water flow from upstream except for local runoff (Hussain and Acharya 1994). It was found that the Sundarbans mangrove forest would be most severely affected by climate change. Due to a combination of high evapo-transpiration and low flow in water, the salinity of the soil would in increase.
As a result the growth of freshwater loving species would be severely affected. Eventually the species offering dense canopy cover would be replaced by non-wood shrubs and bushes, while the overall forest productivity would decline significantly. The degradation of forest quality might cause gradual depletion of rich diversity of the forest flora and fauna of the Sundarbans ecosystem (Shamsuddoha et al. 2007). It is widely believed that if proper measures, such as restoration, regeneration and safeguarding of species and their ecosystem could be adopted for sustainable use, then the Sundarbans mangroves forests alone would become a potential natural resource for Bangladesh. Such a disturbed but economically and environmentally important forest ecosystems demands, a comprehensive ecological investigation both for National and international interests. Owing to the present state of degrading forest resource of Bangladesh, a general consensus has developed that unless some potential measures are adopted quickly. The rest of the forest will disappear soon creating ecological consequences and other natural catastrophe. Various types of research held in different sector of the study area. But no such data are available on the impact of environmental hazards on the diversity of plants. So, the Sundarbans received little attention with respect to the assessment of environmental hazards and their impacts on the floral diversity. Under the circumstances, it has become imperative to institute an investigation on the estimation of environmental hazards and their impacts on the floral communities of the Sundarbans. The present study deals on the impact of environmental hazards on the plant diversity of the Sudarbans-Satkhira range.
The Bangladesh Sundarbans lies between the latitudes 21o 31′ and 22o 30′ N and between the longitudes 89o and 90o E in the district of the Khulna, Bagherhat and Satkhira. It occupies a land area of 401,600 ha, of which 395,500 ha are covered by forests (Chaffey et al. 1985) and comprises 44% of the total productive forest of Bangladesh (Anon 1989). Of the total area, approximately 70% lands and 30% are waters. The distance between the northern and the southern boundaries averages about 80 km, although the distance between the extremities is about 100 km. The east to west distance within Bangladesh is about 80 km. The Bangladesh Sundarbans is a ReservedForest and has been divided into four administrative Ranges with 55 compartments. The forest is flat with a slope of 0.47cm/km and the maximum ground elevation is 3m above the mean sea level (Siddiqui 2001).
River systems:
A complex network of streams and rivers varying considerably in width and depth intersects the entire area. Some of the big rivers are several kilometers in width. The Sundarbans receives large volumes of fresh water from inland rivers flowing from the north and of saline water from the tidal incursions from the sea. The fresh water is charged with alluvium containing plants nutrients. This together with the salinity of the tidal water is the major factor determining the productivity of the forest ecosystem (Siddiqui 2001). At a comparatively recent period, all of the rivers were connected with Ganges. Now, only the Baleswar has direct connection and is responsible for fresh water supply to the eastern part of the Sundarbans. A number of rivers namely the Passer, the Sipsa, the Arpangasia, the Malancha and to slight extent the Jumuna and the Raimangal have indirect connections and receive the overflow of the Ganges during the rainy season. They also receive a considerable amount of local drainage throughout their long and meandering courses during the monsoon (Siddiqui 2001).
Raimangal estuary:
The rivers that contribute their water to this estuary are Harinbanga, Raimangal and Jamuna (Mamdut). The Kalindi river from the international boundary between India and Bangladesh, and takes the name Raimangal towards the south as it flows through the Sundarbans. The Jamuna, originating from Kishenganj in India, bifurcates at Bangsipur where it is called Madder gang and flows through the north of Sundarbans. Further south, it empties into the Bay of Bengal taking the name Jamuna again. This river is connected with the Malancha Faringi gang and with the Rimangal through Atarabankhi and some other connecting channels (Siddiqui 2001).The rivers that drain this estuary are the Malancha and the Barapanga. The latter is formed by the Bal river and the Arpangasia. These two rivers in turn receive that originate out side the Sundarbans. Arpangasia receives water through the Khulpetua and the Kobadak while the Bal river is connected with the Sipsa system through Jafa and to the Kobadak system through the Andarmanik khal and Chalki gang.The estuarine rivers are maintained by runoff from internal rivers such as Kobadak- and Betna. Major estuaries important for navigation e.g., the Passur and the Sipsa, receive fresh water principally from the Goari-Madhumati system. The Baleswar Haringhata estuary is dominated by tidal exchange with Meghna and to a lesser degree with the Padma through Arialkhan. In general, the estuaries of the west are classified as part of the moribund delta while estuaries of the eastern region are part of the active delta. The rivers in the west are strongly influenced by tides. In the east they are tide dominated during the dry season and less so during the wet season (Siddiqui 2001).
Soil characteristics:
Mangrove soil differ from other inland soils in that they are subjected to the twin effects of salinity and water logging, both of which are detrimental to the normal functioning of plant life. Tidal inundation and low water table, combine with poor drainage, generally lead to characteristically saturated water condition, low oxygen content and sometimes free hydrogen sulphide in mangrove soils. These soils are often semi-fluid and poorly consolidated (Hossain and Acharya1994).In general the Sundarbans soil is finely textured and the sub-soil is stratified and at greater depth is compacted (Choudhury 1968). Hasan and Mazumder (1990) mentioned that soils were slightly calcareous, uncured are partly cured clayey deposits which were homogenous both vertically and horizontally. In the eastern part of the forest, where the rivers supply fresh silt every year, the top layer is soft and fertile. In the western Sundarbans where there is little fresh supply of silt, even the surface soil settled down to a hard mass, and the ground is much less suitable for fast tree growth (Siddiqui 2001).
The Sundarbans is located south of the Tropic of Cancer and at the northern limits of the Bay of Bengal and may be classified as tropical moist forest after the Holdridge (1964) system. The coolest temperatures occur during December- January, and the warmest at the end of the dry season, during May-June (Hossain and Acharya1994). The four main season are pre-monsoon (March-May), monsoon (June-September), post-monsoon (October-November) and dry winter Season (December-February). The pre-monsoon season is characterized by southerly winds, high temperatures and evapotranspiration rates with occasional heavy thunder storms and norwesters. The area is inundated by tidal water increases and, due to increasing maritime influence, the salinity of river water also reaches a maximum during this season. The monsoons bring high rainfall, humidity and cloud cover. Sediment load and water levels of rivers also increase due to heavy rainfall in upper catchments areas. The post-monsoon season is hot and humid, sunny with heavy dew fall at night. Occasional thunder storms, cyclones and storm surges and rising salinity levels of river water occur during this season while the dry winter season is characterized by cool, dry and sunny weather with low precipitation. Tide levels remain low and large areas of the Sundarbans experience a dry, exposed period with no tidal inundation (Hossain and Acharya1994).
Rainfall:
Rainfall increases from west to east and the mean annual rainfall within the forest varies from about 2000mm in the east and it is 1600mm in the west. Eighty to eighty five percent of annual rainfall occurs during the monsoon season from May to September. Frequent and heavy showers occur from the middle of June to the middle of September. Precipitation budgets for the region show that for the region as a whole, there is a severe six month dry season when precipitation falls short of meeting evapotranspiration demands by almost 20 inches or 500mm. This is most severe between February and April when soil moisture is at its lowest for the entire year. During this period, the only water available for transpiration is the surface water in the rivers and creeks (Hossain and Acharya1994).
Temperature:
The temperatures in the Sundarbans are more equable than those of the adjacent land area. High temperatures occur from the middle of March to the middle of June. Cold weather commences at the beginning of December and warmer weather sets in at the end of February. The mean annual maximum temperature has been recorded as 31.30C at Satkhira, to the west of the Sundarbans, whiles the mean annual maximum 29.40 C. The mean maximum temperature for the hottest month has been recorded as 32.40 C at Patuakhali in the east of the Sundarbans (Hossain and Acharya1994).
Relative humidity:
Mean annual relative humidity varies from 70% at Satkhira to 80% at Patuakhali. June-October is the months with high humidity while humidity is lowest in the month of February. During the winter months rainfall is very low, but there are thick mists which contribute greatly to the humidity (Hossain and Acharya1994).
Wind:
Due to monsoonal variation of the climate there are variations in wind direction. The south-westerly monsoon starts from the middle of March, and recedes end of the September. The monsoon winds blow from the south with sustained force from March to October. The prevailing winds are from the north and northeast in January. February is a calm month with foggy weather in the mornings (Hossain and Acharya1994).
Cyclones:
Violent cyclonic storms crop up frequently from the middle of May to middle of June due to north coastal winds. Severe cyclones may also occur in October and early November. As a rule, autumnal storms last longer and are accompanied by rain. They may also be accompanied by tidal surges. Both the storms and tidal surges can cause severe damage to forests and human settlements (Hossain and Acharya1994).
The present investigation consisted of three basic methodological approaches, viz,: (i) Field observations and vegetation study (ii) Physico-chemical properties of water; and (iii) Physico-chemical properties of soil. The mangrove plant species were recorded and collected round the three years of the different five spots in every summer, monsoon, post-monsoon and winter seasons from March 2006 to February 2009. Water and soil samples were also collected for laboratory analysis in the same four different seasons to determine physical, chemical and nutrient status. Relationship between water and soil properties and importance value percent of the mangrove plant species were also statistically evaluated.
Selection Of The Sampling Spots
A total of 5 (five) sampling spots were selected for this research works covering almost all the main mangrove regions of Satkhira range. The study spots and their abbreviated field demarcations are as follows:
Name of mangrove forest spots and their symbolic representation are given below-
Koikhali forest area (Spot-1)
Kadamtala forest area (Spot-2)
Burigoalini forest area (Spot-3)
Kalagachia forest area (Spot-4)
Kobadak forest area (Spot-5)
DESCPIPTION OF THE SAMPLING SPOTS
SAMPLING SPOT – 1 (KOIKHALI FOREST AREA)
The first sampling spot Koikhali is situated 70 km away form Satkhira main town. It is situated 13 km western side of Kadamtala Forest Station. It is 2 km away form Koikhali forest station and situated on the river Kalindi. It is upper part of Raymongal estuarie. This spot consists with three sites.
Site - I(Bokchara): Bokchara site is the eastern part of Kalindi river and 2 km south form Kadamtola forest station. This site is inundated during the period of high tide and is flat or slightly sloping. There is soil erosion in this site and it is rich with diverse plan population.
Site - II (Golakhali): Golakhali site is situated on the bank of the river Mamdu. It is the eastern part of Mamdu river and 1.5 km south eastern side away form Koikhali forest station. This is rich with diverse flora and inundated during the high tide.
Site - III (Mathavanga): Mathavabga is situated on the bank of the river Mirgang. It is about 2 km east form Koikhali forest station. This stand is comparatively high and the river erosion in this site is minimum. It is rich with diverse plant population.
Sampling Spot – 2 (KadamtalaForest Area)
It is located at Kadamtala forest station which is 77 km away form Satkhira main town. It is situated on the bank of the river Chunkuri. It is upper part of the Jamuna-Malancha estuaries and is about 13 km east from Koikhali forest station. This spot also consists with three sites.
Site - I (Chunkuri): Chunkuri site is 1km west form Kadamtala forest station. This area inundated during the period of high tide and is situated on the river Chunkari. This site is flat or slightly sloping.
Site – II (Kadamtala):This site is located to opposite of Kadamtala forest station. It is eastern part of Kadamtala khal. Erosion is minimum here than other site. This site is moderately sloping and inundated during the period of high tide.
Site - III (Kalukhali): Kalukhali is located in the western side of Kalukhali khal. It is about 1km away form Munsigonj and it is rich with diverse plant population.
Sampling Spot – 3 (BurigoaliniForest Area)
This spot is very close to the Burigoalini forest station, which is 72km away from Satkhira main town. This spot is mostly disturbed by tourist and fish fry collector. This spot consists with three sites.
Site – I (Choto Kewakhali): This site is situated on the bank of the River Arpangasia which is about 1 km south from Burigoalini forest station. This forest is separated in north south in to two part by a small channel namely Choto Kewakhali khal.
Site - II (Gagirteck): This area is just opposite to the Burigoalini forest station and it is situated on the bank of the river Arpangasia. Most of the places are plain, sometimes slightly elevated.
Site - III (Dathnekhali): This site is situated on the bank of the river Chuna and 1km north from Burigoalini forest station. The land of this forest area is seen to be quite elevated, but under the effect of the tidal water flowing regularly.
Sampling Spot – 4 (Kalagachia)
This spot is situated on the bank of the river Kalagachia which is about 4 km south from Burigoalini forest station. Most of the forest floor is inundated frequently. There are many small canals and depressions inside the forest. Soil is clayey to clayloam and almost wet due to frequent inundation. This spot is consisted of 3 sites.
Site - I (Khalisabunia): This site is just the opposite side of the Kalagachia forest camp and is situated on the bank of the river Kalagachia-Arpangachia. Most of the place is more or less plain, sometimes slightly elevated. The habitats are observed to be frequently inundated and soils are mostly clayey that might be due to the flowing tidal water.
Site - II (Pashurtala): The site is about 1.5 km southern side form Kalagachia forest camp which is situated on the bank of the river Kalagachia. In this site, there is minimum soil erosion and the site is rich withmangrove plant population. This area is inundated during the period of high tide.
Site -III (Kewakhali): This site is situated near Kewakhali Khal which is about 1km north from Kalagachia Forest Camp. Most of the forest floor inundated frequently. There are many small canals and depressions inside the forest. Erosion is comparatively high in this site and it is rich with diverse plant populations.
Sampling Spot -5 (KobadakForest Area)
This spot is about 6 km east- southern side from Kalagachia Forest Camp which is situated on the bank of the river Kobadak- Arpangasia system. Kobadak sampling spot is basically a frequently inundated habitat with very thin vegetation. Soil of this site is wet, sandy- loamy in river side and clayey inside the forest. Interference and encroachment due to the presence of seasonal fishermen’s settlement is notable in this forest. This spot is consisted of 3 sites.
Site - I (Katteshar): The name of this site is Katteshar which is about 2 km west from Kobadak forest station. There are many small canals and depressions inside the forest. The soil of this forest is sandy-loamy, wet or slightly clayey. Most of the places are more or less plain sometimes slightly elevated.
Site - II (Sapkhali): This site is just opposite side of the Kobadak forest station and is situated on the western bank of the river Arpangasia. Soil erosion is lower here than other sites. The habitats are observed to be frequently inundated and soils are mostly sandy-loamy that may be due to the flowing of tidal water.
Site- III (Shannashichar): The name of this site is Shannashichar which is about 2 km south western side from Kobadak forest station. The trees of all associated species are observed to scattered. The land of this forest area is quite elevated, but under the effect of tidal water flowing regularly. The soil near the canal, i.e. at the edge of forest is sandy-loamy and non clayey and that inside the forest is compact loamy, covered by a thin layer of slippery clay.
There is a decrease in canopy closure in recent years. In 1960, 78% of the total area of the Sundarbans had a canopy closure of 75 % or more. A survey made in 1985 showed 65% of the forest as having a canopy closure of 70% or more. In 1996, the situation worsened further. Pre-dominant canopy classes are those having only 30% or more closure. In general, the forest is more closed in the east than in the west. The canopy closure in the east is usually more than 70%, in the middle part it is between 30 and more than 70% and the western part has from 30 to less than 70% (Siddiqui 2001).
Vegetation Study
Satkhira rage was selected on the experimental area. This area is strong saline zone. Every sampling spot was divided into-3 sites mainly on the basis of sloping, vegetation, age and soil erosion etc. The selected sites in all the sampling spots were treated as “permanent sample plots”.
Selection of sampling season:
The Sundarbans, mangrove ecosystems is dynamic and complex. Changes of vegetation are continuous. The mangove plant species of the different sample plots were recorded and collected round the three year with every Summer, Monsoon, Post-monsoon and winter seasons from March 2006 to February 2009.
Determination of quadrat size:
Mangrove plants investigation was performed by random quadrat method. In the present investigation quadrat size was determined by a more or less constant presence of plant species and in this regard ‘Species area curve’ (Ambasht 1990) was determined first. 5m×5m size was found to be most convenient quadrat size. Thus 5m×5m quadrat was considered finally for permanent spots for vegetation sampling in all the permanent sampling plots.
Vegetation recording and sampling:
In each permanent sampling plot, at least 20 quadrats were applied randomly. Plants names including local name, habits, life-form; (Raunkaier 1934) and economic uses of individual plant species was recorded. Samples of recorded plants were also collected in a view to build up small herbarium on ‘Mangrove Forest Flora of Satkhira range’. In this way, vegetation recording and sampling were accomplished in “SatkhiraRange” area of all five study spots during summer, monsoon, post-monsoon and winter seasons. Frequency status of existing plant species among the five areas was observed and dominance categories were determined.
Phytodiversity analysis:
The quantitative phytodiversity attributes density, relative density, frequency and relative frequency and importance value percent (IV %) of each attributes were analyzed and computed by following formulae.
Total number of individual s of a species in all the quadrat
i. Density (D) = -----------------------------------------------------------
Total number of quadrat studied.
Total number of invividual s of a species
ii. Relative density (D3) = ---------------------------------------------------- X 100
Total number of individual s of all the species.
Number of quadrat in Which species occurred
iii. Frequency (F) = ---------------------------------------------------- X 100
Total number of quadrat studied
Frequency of the species
iv. Relative frequency (F3) = ---------------------------------------- X 100
Total frequency (F) of all the species
v. The importance value percent (IV%) for each species was calculated by adding relative density (D3), relative frequency (F3) and dividing it by 200 and multiplied by 100.
PHYSICO-CHEMICAL CONDITIONS OF WATER
In every water sample were collected from all the permanent sampling sites. Then immediately different parameters of the samples were analyzed using the following standard methods.
PHYSICO-CHEMICAL CONDITIONS OF WATER
In every water sample were collected from all the permanent sampling sites. Then immediately different parameters of the samples were analyzed using the following standard methods.
WATER TEMPERATURE
Centigrade thermometer was used to determine of water temperature.
WATER SALINITY
Water salinity was recorded by using Hand Refractometer. The result was expressed in ppt.
HYDROGEN-ION CONCENTRATION OF WATER (pH)
Water pH was measured by HANNA digital pH meter (Model H198107).
Winkler’s method (unmodified) was followed for the estimation of dissolved oxygen. The water samples collected for dissolved oxygen estimation were treated with manganous sulphate solution, alkaline iodide solution and acidified with concentrated sulphuric acid on the spot. The treated samples were transferred to the laboratory and the remaining steps of analysis were done. No noticeable change occurred in the treated samples within 24 hours. The quantity of dissolved oxygen, thus estimated, was expressed in milligram of oxygen per liter of water (mg/l).
BIOCHEMICAL OXYGEN DEMAND (BOD)
The sample of BOD bottles were filled with water and immediately transported to the laboratory and left for incubation in 20oC for five days. Dissolved oxygen (DO) content of BOD bottle water sample was determined after five days by following the Winkler method (unmodified). The value of BOD was obtained by subtracting final dissolve oxygen (FDO) from initial dissolve oxygen (IDO).
When the DO content was almost negligible or showing a condition of total anoxia, the BOD was determined by dilution method (APHA 1989).
