Heritiera Fomes Research Articles

Why some trees are more vulnerable during catastrophic cyclone events in the Sundarbans mangrove forest of Bangladesh?

Mangroves are recognised for their diverse set of ecosystem services, including protection from tropical cyclones and tidal surges. Mangroves are also adapted to withstand disturbances across a range of climatic conditions, and the frequency and severity of disturbances are projected to increase in the coming years due to climate change and sea-level rise. The Sundarbans of Bangladesh and India is one of the most frequently affected mangrove forests in South Asia. We investigated the effect of cyclone disturbance and stand characteristics on the survival of two dominant mangrove tree species – Heritiera fomes and Excoecaria agallocha. Data was collected through field surveys after cyclone Sidr, a category 5 cyclone that struck in the area in 2007, creating substantial forest damage. We used a Generalized Additive Mixed Model to analyse the effect of tree species, stem diameter at breast height (dbh), and tree spatial position in the forest stand on the degree of cyclonic damage. We find that cyclonic damage in the Sundarbans forest is sensitive to species and dbh. At similar tree size, Heritiera fomes was more vulnerable to cyclonic damage than Excoecaria agallocha. In Heritiera fomes the intensity of wind damage during cyclone increase with increasing dbh. In Sundarbans, cyclonic damage also depended on stand factors such as proximity to the riverbank or forest edges. We suggest silvicultural treatments, such as increasing the tapering of crown or decreasing height/dbh ratios of valuable species, could minimise future cyclonic damage in the area. Further investigations are necessary to improve the management of mangroves in the Sundarbans in the face of climate change, sea-level rise, and novel anthropogenic pressures.

Litterfall assessment and reproductive phenology observation in the Sundarbans, Bangladesh: A comparative study among three mangrove species

Bangladesh has the single largest mangrove forest in the world, which is under threat from catastrophic disturbance and anthropogenic pressure. The study investigated monthly reproductive litterfall and correlated with climatic factors from March 2016 to February 2018. We applied circular statistics to detect seasonal trends of reproductive litterfall of Heritiera fomes, Xylocarpus mekongensis and Bruguiera sexangula in the Sundarbans. Although flower and fruit fall of H. fomes and X. mekongensis occurred for a specific period. But B. sexangula continued throughout the year. Flower fall of all three species peaked during March. Fruit fall of H. fomes, and X. mekongensis peaked during July and August respectively and the propagule fall of B. sexangula peaked during July. The highest proportion of flower fall was recorded in B. sexangula (2.13 ± 0.29 Mg ha−1year−1) followed by X. mekongensis (1.23 ± 0.07 Mg ha−1year−1) and H. fomes (1.06 ± 0.09 Mg ha−1year−1). But the highest fruit fall was recorded in H. fomes followed by X. mekongensis and B. sexangula. Annual flower and fruit fall were significantly different (p < 0.05) among the species. Mature fruit falls of the studied species were significantly correlated with temperature, rainfall and relative humidity but flower and immature fruit falls were significantly correlated with temperature, maximum wind speed and day length rather than tree size and biomass production.

Leaf morphological plasticity in three dominant tree species in the Sundarbans mangrove forest of Bangladesh in different salinity zones

Mangrove tree species show plasticity in their leaf morphological traits in different salinity zones. However, leaf morphological plasticity and its causes in different salinity zones are incompletely understood. To understand the mechanism of plasticity, this study investigated the responses of three dominant tree species Sundri (Heritiera fomes), Gewa (Excoecaria agallocha) and Goran (Ceriops decandra) of the Sundarbans to the salinity gradients. A total of 17 leaf parameters were measured and quantified. All collected data were analyzed using univariate and multivariate statistical tools to investigate leaf morphological plasticity. A wide range of phenotypic plasticity was observed in all leaf parameters studied among the salinity zones of the Sundarbans. One-way ANOVA and Tukey’s posthoc test revealed significant differences (P < 0.05) in all leaf parameters among the salinity zones and confirming that there was a high degree of phenotypic plasticity among the salinity zones of the Sundarbans. Petiole length (PL), leaf area (LA) and leaf length/petiole length (LL/PL) showed high level of plasticity among the salinity zones of the Sundarbans for each species of Sundri, Gewa and Goran. Plasticity index (PI) was developed in this study for each species studied. High level of phenotypic plasticity in these leaf traits reflects fitness of these species to different saline environments. Our results provide clear evidence that all the leaf parameters measured for three tree species viz., Sundri, Gewa and Goran effectively utilizes a plastic strategy in different salinity zones in the Sundarbans. Morphological trait plasticity could serve as powerful biological indicators to predict the shift of leaf morphology in upcoming environmental change events like sea level rise and reduction of fresh water flow from upstream.

Screening of Antimicrobial and Antioxidant Activity of Acetone Extracts of Heritiera fomes Whole Plant against Pathogens

Background: Phytochemicals are well known to have many important pharmaceutical properties. Heritiera fomes grows in low saline environments. The present study was initiated to explore the biologically beneficial properties of H. fomes. Methods: The crude extracts of H. fomes were extracted in acetone by orbital shaker and concentrated using rota evaporator. Total flavonoid content and Total phenolic content were estimated spectrophotometrically and the in-vitro antioxidant capacity was estimated by DPPH (2,2-diphenyl-1-picrylhydrazyl), Ferric Reducing Antioxidant Power (FRAP) and Hydrogen peroxide (H2O2) Scavenging Assays. Anti-microbial activity was determined by Disc diffusion method. Results: Phytochemical screening of acetone extract of H. fomes showed the presence of major classes of phytochemicals like alkaloids, glycosides, flavonoids, saponins, carbohydrates, phenols and sterols in considerable quantity. The total amount of phenolic and flavonoid content was found to be 75.3 mg GAE/g dry weight and 61.3 mg QE/g dry weight respectively. Antioxidant activity of plant extract determined by using different assays like H2O2 radical scavenging, DPPH and FRAP. A positive correlation between all the pairs of antioxidant assays was observed. Further, antimicrobial activity against various pathogens was evaluated by disc diffusion method where the zone of inhibitions were found to be in range from 5± 0.35 to 12 ± 0.50 mm. Conclusion: The study concludes that the plant Heritiera fomes has its effect in scavenging free radicals and has a potential to be a power antioxidant. Several in-vitro studies possess significant antioxidant, antimicrobial activities. The present study plays an important tool for new drug discovery.

Predicting multi-enzyme inhibition in the arachidonic acid metabolic network by Heritiera fomes extracts

Heritiera fomes is a mangrove plant with a rich history of ethnomedicinal usage against chronic inflammation. Biochemical analyses of H. fomes have exposed a plethora of bioactive phytochemicals that contribute to this therapeutic effect by perturbing enzymes of a complex inflammatory network mediated by arachidonic acid (AA) metabolism. This study is the first instance of utilizing cheminformatic approaches to elucidate a molecular linkage between these phytochemical interventions and the multi-enzyme AA metabolic network regulation. Analysis of the simulations reflects H. fomes as a functional reservoir of multiple safe and potent natural anti-inflammatory compounds. The investigation suggests two phytocompounds extracted from the plant: a sesquiterpene lactone and a flavone glycoside, as candidate inhibitors of multiple catalytic checkpoints of the inflammatory network. The outcomes of this research act as a primary guideline for future laboratory and clinical testing of anti-inflammatory potentials of H. fomes as an exploitable source of safe and potent drug-like molecules. Communicated by Ramaswamy H. Sarma

Molecular identification and antimicrobial activity of endophytic fungi isolated from Heritiera fomes (Buch. -Ham), a mangrove plant of the Sundarbans

BackgroundEndophytic fungi play a vital role in plant defense system by secreting various antimicrobial agents. To evaluate the antimicrobial activity of the endophytic fungi of the mangrove plant Heritiera fomes (Buch. -Ham), plants were collected from the Sundarbans, Bangladesh. The endophytic fungi were subsequently isolated and identified.ResultsFifty-five endophytic fungi were isolated from the leaves, root, and bark of H. fomes (Buch. -Ham). Genomic DNA was extracted for PCR (polymerase chain reaction) by specific primers to multiply ITS region and sequences were determined. Nucleotide sequence data were submitted to the Genbank and accession number for each fungal strain was obtained. Antimicrobial activity of the ethyl acetate (EtOAc) and methanolic extracts of eleven species from both fermentation and mycelium, respectively, were analyzed by microtiter plate-based antimicrobial assay incorporating resazurin as an indicator of cell growth against two Gram-positive bacteria namely Staphylococcus aureus NCTC 12981 and Micrococcus luteus NCTC 7508, two Gram-negative bacteria namely Escherichia coli NCTC 12241 and Pseudomonas aeruginosa NCTC 12903, and a fungus Candida albicans ATCC 90028. All the endophytic fungal extracts exhibited antimicrobial activities against more than one-tested pathogenic microbial strains. Overall, methanolic extracts showed greater activity than EtOAc extracts. Pseudopestalotiopsis camelliae-sinensis, Pestalotiopsis microspora, and Penicillium copticola were the most active endophytic fungal strains and exhibited strong inhibitory activity against the microorganisms under investigation and their MIC values ranged from 0.0024 to 5.0 mg/mL. Methanolic extracts of both P. camelliae-sinensis and P. microspora showed the highest antibacterial activity (MIC value of 0.0024 mg/mL) against P. aeruginosa NCTC 12903.ConclusionThis study showed that the isolated and identified endophytic fungi from H. fomes (Buch. -Ham) could be potential sources of antimicrobial agents.

STUDY OF ANTIMICROBIAL POTENTIALITY OF EIGHT DIFFERENT MANGROVE SPECIES AND DEVELOPMENT OF THEIR INTRA-RELATIONSHIP THROUGH CLUSTER ANALYSIS

Objective: The present study investigates the antimicrobial activities of eight different mangrove plants and also the development of their intra-relationship through cluster analysis.&#x0D; Methods: The dried and powdered leaves of different mangrove species were extracted by cold maceration process with water, methanol, and chloroform. The antimicrobial activity was done using the agar well diffusion method. The cluster analysis of the mangrove plants was analyzed by MINITAB Release 13.1.&#x0D; Results: The order of extraction yield for each mangrove species was methanol &gt; chloroform &gt; water. The methanol extract of Suaeda maritima, Avicennia marina, Avicennia officinalis, and chloroform extract of Sonneratia apetala gave the highest inhibition zones of 19 mm, 19 mm, 19.33 mm, and 19.33 mm, respectively, against Bacillus subtilis. The methanol extract of Ceriops decandra, Xylocarpus granatum, and Bruguiera gymnorrhiza found the highest inhibition zones of 21.67 mm, 22 mm, and 20.3 mm, respectively, against Escherichia coli, Shigella flexneri, and Staphylococcus aureus, respectively. The endangered and endemic species Heritiera fomes gave the highest result (18 mm) against both for Micrococcus luteus and B. subtilis in methanolic extract. The maximum zone of inhibition of fungal strains was found against Botrytis cinerea (15 mm), Fusarium oxysporum (16.33 mm), and Rhizopus oryzae (13.33 mm) with the methanol extract of X. granatum, S. apetala, and C. decandra, respectively. Cluster analysis of 8 mangrove species based on different bacterial pathogens was also shown where it demonstrated their intra-relationship against some bacterial pathogens.&#x0D; Conclusion: From this study, it may be concluded that mangrove plants can be used to discover bioactive natural products.

Impact of increased salinity on the plant community of the Sundarbans Mangrove of Bangladesh

The overreaching objective of the study was to assess the changes in eco-regional forest composition and the colonization of invasive plant species in the Sundarbans, the largest single block of tidal halophytic mangrove forest globally. The study also aimed to examine the relationship between different plant types and the salinity level. Additionally, the interconnection between the salinity and the ‘top dying’ disease of the pioneer and dominant species was also measured. Thirty sample plots were established at the mouths of an equal number of canals to collect the plant community’s primary data. In addition, secondary historical data were utilized to understand the natural dynamics of the forest eco-regions in this mangrove. The study revealed that the fresh swamp forests disappeared from their historical range. Over time, the Screw Pine (Pandanus tectorius) became extinct from the study area. Simultaneously, rice grass (Leersia hexandra) and wild rice (Potresia coarctata) stand on the brink of extinction. Sundari (Heritiera fomes), the pioneer and dominant species, suffers from the increased salinity, and its stocks are declining due to intensified “top dying” disease. In contrast, the salt lover species, notably white mangrove (Avicennia marina), enjoy the incremental hegemony. The abundance of the indicator species, Nypa Palm (Nipa fruticans), and Mangrove Date Palm (Phoenix pelludosa) show a declining trend because of increased salinity. A total number of 25 invasive plant species were enumerated in this study. Immediate mitigation actions are required to protect this alteration in the vegetation composition of this mangrove. Hence, the study proposed a conceptual model of a mitigation plan spotlighting the local pressures.

Comparison of physicochemical and antioxidant properties of edible fruits in the Sundarbans’ mangrove forest, Bangladesh

Ten edible fruits of the Sunderbans’ mangrove forest in Bangladesh were analyzed to compare their physicochemical, nutritional and antioxidant properties. Among the fruits, the lowest pH of 4.2 was observed in Sonneratia caseolaris whereas the rest remains within 6.1 to 7.1. The highest electrical conductivity (596.3 μS/cm), total dissolved solid (298.2 ppm) and ash content (0.26%) were recorded in the fruit of Phoenix paludosa. Carbohydrate, protein, lipid and vitamin C contents were the highest in Avicennia officinalis, Ceriops decandra, Heritiera fomes and Bruguiera gymnorrhiza fruits, respectively. In these fruits, the most abundant macro and micro-elements were K and Fe, respectively. C. decandra showed the highest content of polyphenols (58.5 mg GAE, gallic acid equivalent/g powder), flavonoids (86.4 mg CE, (+)-catechin equivalent/g powder) and anthocyanins (0.39 μmol/g powder). C. decandra also showed the strongest DPPH free radicals scavenging, reducing power, and total antioxidant capacity. Noticeably, total polyphenols showed their strong correlation to total flavonoids (r2 = 0.90), anthocyanins (r2 = 0.81), reducing power (r2 = 0.98) and total antioxidant capacity (r2 = 0.88) of the fruits. Fruits of C. decandra, therefore, should be considered as a potential source of antioxidants followed by H. fomes and P. paludosa.

Selection of mangrove species for shrimp based silvo-aquaculture in the coastal areas of Bangladesh

The purpose of this work was to assemble information with which to help identify and select mangrove species most likely to be useful and locally acceptable for use in transforming the dominant current non-mangrove shrimp culture practice in Bangladesh towards more sustainable shrimp silvo-aquaculture in the coastal regions of the country. We reviewed current mangrove use in the extensive aquaculture setting, compiled published evidence on mangrove properties and characteristics that influence their suitability for such use and assessed farmer preferences of the various species. Thirteen mangrove species (all of which are available in Bangladesh) were documented as being used in silvo-aquaculture system in the tropics. Followed by these already “established” mangrove species, Aegialitis rotundifolia, Heritiera fomes and Lumnitzera racemosa could be enlisted as additional “optional” mangrove species to consider, while Ceriops decandra, Excocaria agallocha and Phoenix paludosa were found to be unsuitable for silvo-aquaculture. Based on their experience and indigenous knowledge on mangroves, shrimp farmers ranked (in declining order of preference) Sonneratia apetala, S. caseolaris, Avicennia officinalis, Nypa fruticans, Bruguiera sexangula, Heritiera fomes, and also, the mangrove-associate wild rice species Oryza coarctata as the most suitable species to be used for promoting silvo-aquaculture in the coastal areas of Bangladesh. Thus, the focus group interviews with the farmers not only identified which mangroves enjoy most local support for use in transforming current shrimp culture towards more sustainable shrimp silvo-aquaculture but also provided additional leads for species interesting to further investigation into their suitability for silvo-aquaculture.

Vegetation Scenarios Of Artificially Planted Mangrove Species in Sundarbans as a tool to Mitigate Climate Change Issues in Bangladesh

Vegetation scenarios of artificially planted mangrove species such as Sundri ( Heritiera fomes Buch.-Ham ), Gewa ( Excoecaria agallocha L), Goran ( Ceriops decandra Griff. Ding Hou), Kankra ( Bruguiera sexangula lour. Poiret), Kirpa ( Lumnitzera racemosa Willd), Khaisi ( Aegiceras corniculatum L. Blanco), Amoor (A moora cucullata Roxb), Jhana ( Rhizophora apeculata Lam) were studied in the Sundarbans which is the world's largest contiguous mangrove forest from 2009 to 2018 in mesohaline and polyhaline zone in Bangladesh. The objectives of this research were to enrich vacant and poorly regenerated areas with a view to increase vegetation cover, biodiversity development, management and thus help to mitigate climate change through sustainable management of the ecosystem of the Sundarbans in this vulnerable delta. In the experimental plantation the average survival percentage of Sundri, Gewa, Goran, Kankra, Kirpa, Khaisi, Goran, Amoor, Jhana were 19%, 59%, 22%, 61%,75%, 54%, 8%, 26% in the polyhaline (&gt; 18 ppt) zone and 22%, 75%, 9%, 47%,51%, 48%, 7%, 5% respectively in the mesohaline (5-18 ppt) zone. Average height (m) of the planted trees of eight species in the mesohaline zone were 3.18 m, 5.38 m, 4.54 m, 7.01 m, 3.71 m, 2.63 m, 1.53 m, 7.74 m and average DBH (cm) of the tree species measured 2.14 cm, 3.68 cm, 3.78 cm, 5.77 cm, 2.66 cm, and 7.5 cm respectively Besides average height (m) of eight species in the polyhaline zone were 2.84 m, 5.42 m, 4.47 m, 6.74 m„ 3.74 m, 2.82 m, 1.04m, 7.48 m and average DBH of Sundri, Gewa, Goran, Kankra, Kirpa, Khaisi, Jhana (cm) were1.35 cm, 4.17 cm, 4.48 cm, 6.09 cm, 3.34 cm, and 8.04 cm respectively Therefore, it can be mentioned that Gewa, Goran and Khalshi in polyhaline zone showed better survival percentage and Jhana, Kirpa along with other species showed satisfactory growth performance in mesohaline and polyhaline zone simultaneously

Litterfall release, vegetative, and reproductive phenology investigation of Heritiera fomes Buch-Ham in the Sundarbans mangrove forests, Bangladesh: relationship with environmental variables

The study of vegetative and reproductive phenology through litterfall collection of mangrove species is vital for mangrove management and restoration in climate change situation. This study was carried out to investigate vegetative and reproductive phenological pattern of Heritiera fomes using litterfall data in the Sundarbans, Bangladesh for a period of 24 months. Leaf and stipule litterfall released throughout the year with a distinct periodic pattern. Vegetative litterfall (981.9–1211.3 g/sq m/yr) contributed 59.3% of total litterfall (1791.1–1907.3 g/m/yr). The order of vegetative litterfall was leaf > branch > stipule. Peak flowering and mature fruit litterfall were noticed in April (1.52 times of mean monthly flower production) and July (1.56 times of mean monthly production), respectively. Analysis of variance (ANOVA) showed significant difference (p < 0.05) among monthly litterfall productions, whereas t-test showed no significant difference (p > 0.05) of litterfall production between two successive years during study periods. Vegetative and flower litterfall were significantly influenced by maximum wind speed, mean monthly temperature and day length. On the contrary, mature fruits were significantly correlated with rainfall.

Leaf morphological and anatomical plasticity in Sundri (Heritiera fomes Buch.-Ham.) along different canopy light and salinity zones in the Sundarbans mangrove forest, Bangladesh

Sundri (Heritiera fomes Buch.-Ham.) is an evergreen mangrove tree species found abundantly in the freshwater zone of Sundarbans, Bangladesh and scattered in moderate or strong saline zones of the forest. H. fomes grows well in top canopy having full sunlight and even in full shade under the canopy. This study presents the plasticity of leaf morphological and anatomical characteristics in H. fomes due to variation of light intensity at different canopy depths and of salinity in different saline zones of Sundarbans. This study was conducted in two steps, firstly the light intensity and leaf phenotypic variations at different canopy depths (one-meter interval) in the fresh water zone of Sundarbans, secondly the leaf phenotypic variations in three saline zones having variable light environment at different canopy positions (top, middle and bottom) in each zone. Leaf samples were collected from three different salinity zones and each canopy positions and various morphological and anatomical characteristics were quantified. A wide range of variations were observed in the leaf parameters measured among the salinity zones of the Sundarbans and the canopy positions. The canopy of H. fomes showed an exponentially decreasing light gradient. Leaf plasticity index (PI) of all the parameters was developed for the salinity zones and the canopy positions of the Sundarbans. The ordination plots (PCA) suggested clear morphological and anatomical shift of the samples collected from different saline zones and canopy positions showing relationship to light and salt stresses in natural environment. Our results provide clear evidence on plastic strategy of H. fomes against salinity and light gradients in the Sundarbans.

Canopy gaps influence regeneration dynamics in cyclone affected mangrove stands in medium saline zone of the Sundarbans, Bangladesh

Regeneration in the canopy gaps in medium saline zone of the Sundarbans Reserve Forest (SRF), Bangladesh was studied to investigate either significant floristic and structural differences between canopy gaps and adjacent forest with continuous canopy. A total of eighteen plots (30 m × 20 m) with an area of 1.08 ha were sampled from six sites (three sample plots from each sites). Species richness in terms of total number of species (seedling, height < 1.5 m) in the study area was not significantly different between canopy gaps and continuous canopy, but there was still difference in floristic composition. Heritiera fomes and Excoecaria agallocha were the dominant and co-dominant seedling species in both sites but the study demonstrated that Ceriops decanrda, Aegiceras corniculatum and Phoenix paludosa were restricted only in canopy gaps whereas Bruguiera sexangula, Brownlowia tersa, Cerbera manghas and Petunga roxburghii were restricted only in continuous canopy. The study also revealed significant difference of seedling density between gaps (43,454 ha−1) and continuous canopy (28,237 ha−1). The density of H. fomes was significantly higher in canopy gaps (38,952 ha−1) than under continuous canopy (15,298 ha−1). Shannon diversity index (0.41 in gaps and 0.82 in canopy) was significantly reduced (50% of canopy) in the gaps. Our study concluded that canopy gaps enhanced colonization of H. fomes seedlings in the medium saline zone than does of floristic composition and species diversity. The study demonstrate that information on seedling dynamics in the canopy gaps may be important for management and conservation of the SRF.

Spatiotemporal mapping mangroves of Tengragiri wildlife sanctuary under Barguna district of Bangladesh using freely available satellite imagery

Naturally grown mangrove forest is the south coastal community’s green barrier from any type of hydro-meteorological hazard and disasters. South-western coastal area of Bangladesh is covered by the Sundarbans, and mid-central zone is covered by Tengragiri wildlife sanctuary which is taken as a protected area in this recent era but not mapped properly with considering different species diversification and temporal changes pattern which is required for successful co-management of this mangrove forest. This study identifies species composition, plant diseases, degradation of the mangrove forests and further focuses on mapping mangroves by conducting plotting-based primary field visit, variability analysis using different indices and cross-matching with secondary databases. Existing mangrove forest boundary’s 200 m buffering with three-time series satellite imagery 2000, 2010 and 2017 is considered for further analysis. Including all buffering zone, this protected area considered 9 major classes that included four subclasses for presenting result like Baen (Avicennia officinalis), Gewa-Goran (Excoecaria agallocha, Ceriops decandra), Keora (Sonneratia apetala), Sundri (Heritiera fomes), Plantation trees Samanea Saman (Raintree), agriculture-grassland (agri-grass) and homestead settlement, sandbar and waterbody. Mapping accuracy assessment purpose automatically generated 996 points cross-matched with previously mangrove species level detailed survey results and found highest accuracy in Sundri species (70%) and all others above 50%. During 2000–2017, the Keora area showed the highest increase 129% over 2000 and increasing rate 13.17 ha/yr. About 26% Sundri and Baen–Passur increased around 13.45 ha/yr. In case of Sundri, 70% area coverage remained intact during 2000–2017, while other 25% classified in 2017 as Avicennia officinalis, Gewa-Goran classes. Furthermore, using refracted electromagnetic energy from various physical characteristics of plants application, four indices (NDVI, DVI, MSAVI-2, RVI) are usable where single-species-level crop density analysis has limitations, but identification of Sundri and Keora by MSAVI-2 and NDVI found significant and alternately lower accuracy values from RVI. Identification of dominant mangrove species groups as well as area gains and losses over 2000–2017 is a robust biophysical baseline for management of the sanctuary. Natural hearts of this area and working as first-step warriors against natural disasters originated from Indian Ocean and Bay of Bengal; so far, it is very much required to save this forest and the coastal communities as well. The results of the study and maps will be helpful for the scientific community, planners, government-international bodies and the activists, Forest Department and the local community in effective planning, monitoring the effectiveness of co-management in conservation of the sanctuary.

Mangrove species diversity, stand structure and zonation pattern in relation to environmental factors — A case study at Sundarban delta, east coast of India

The forest structure and its relation to environmental parameters of Sundarbans, largest mangrove habitat in India, are presented. Quadrat method was used to analyze the vegetation-environment interaction and structural maturity of mangroves. Floristic studies revealed twenty-seven mangrove species including the critically endangered Sonneratia griffithii and endangered Heritiera fomes. Based on Importance Value Index, Avicennia marina, Excoecaria agallocha, Avicennia officinalis and Avicennia alba were designated as the most important species. Higher diversity indices were observed (Shannon index, ranged from 4.2-1.8; Pielou’s index, 0.96-0.91) revealing greater species diversity and even dispersion of mangroves in Sundarbans. Stem density varied from 133 to 19333 ha−1 and individual basal area 0.4 to 13.4m2ha−1. A very low Maturity Index Value was recorded indicating a low degree of structural maturity. Most of the vegetation parameters (density, species diversity index, β diversity) and few of the edaphic parameters (pH, grain size, total carbon) were found to be in better condition; however, salinity showed significant negative correlations with vegetation characteristics. The study revealed a mixed species composition with intermediate structural development indicating a growing forest in Sundarbans. The data evolved in the study would be fundamental in site-specific management and conservation efforts of mangroves in this world heritage site.

Micronutrient Contents of Heritiera fomes Species at Three Saline Zones of the Sundarban Mangrove Forest, Bangladesh

Micronutrient or essential heavy metals viz. Copper (Cu), Zinc (Zn) and Iron (Fe) distribution trend were studied at the age of 6, 9 and 30 months old Heritiera fomes seedlings at three distinct saline zones viz. Chandpai (Oligohaline), Jungra (Mesohaline) and Munshiganj (Polyhaline) of the Sundarban mangrove forest. Among the observed micronutrients, Fe content comparatively lower than Cu and Zn. Relatively higher Cu was found in the root of 6 month age Heritiera fomes seedlings grown at the Chandpai (Oligohaline) zone but higher content of Zn was found in the both root and the shoot. At the 9 month age, comparatively higher content of Cu was found in the root of the seedlings grown at the Jungra (Mesohaline) zone but in the shoot, comparatively higher Cu content was observed in the seedlings grown at the Munshiganj (Polyhaline) zone. At the age of 30 months, Cu and Zn both contents found comparatively lower. At the same age (30 months) Fe content was found relatively higher in the root and the shoot of H. fomes seedlings grown at Chandpai saline (Oligohaline) zone but lower in 6-month-old seedlings. At the older age seedlings may appear more metal tolerant/avoider than the younger age seedlings.

In vitro callus induction from nodal and leaf explants of Heritiera fomes Buch - Ham: An endangered mangrove

Heritiera fomes (an important threatened mangrove) belongs to the family Sterculiaceae, is well known to be used as folk medicine for curing heart diseases, diabetes, pain, diarrhoea, skin disorders and hepatic disorders. Moreover, the ethanolic extract of stem bark had been reported to have the properties like antioxidant, lipoxygenase inhibitory, antihyperglycemic, antinociceptive effects and antibacterial activities. Being an important species, its multiplication is must. But in general, its multiplication through seeds is difficult due to having problems of seed collection, habitat type, seed viability and short storage life of seeds. In contrary, in vitro micropropagation could be one of the options. Hence, a study was conducted to investigate the callus induction from nodal and leaf explants of H. fomes under in vitro micropropagation for development of a protocol for future work. The result revealed that, the MS (Murashige and Skoog) medium containing BAP (2.0 mg/l) + NAA (1.0 mg/l) was found to be the most suitable for callus induction and mass of callus (i.e., fresh weight and dry weight) from nodal explants and the MS medium containing BAP (2.0 mg/l) + NAA (2.0 mg/l) was best for the callus induction and mass of callus (i.e., fresh weight and dry weight) from leaf explants of H. fomes.

EFFECT OF SALT STRESS ON CHLOROPHYLL AND PROLINE ACCUMULATION IN LEAVES OF Heritiera fomes Buch.-Ham. AND Xylocarpus moluccensis (Lam.) M. Roem. SEEDLINGS REGULATING ITS SURVIVAL AND GROWTH

Heritiera fomes Buch.-Ham. and Xylocarpus moluccensis (Lam.) M. Roem. are the two most important trees of the Sundarbans. Survival and biomass increment, chlorophyll and proline concentration in leaves were investigated in seedlings of the two species grown at different levels of salinity in hydroponic culture. Seedlings were grown at 0, 5, 10, 15, 20, 25, 30 and 35 ppt salinities for 90 days. Significant reduction of chlorophyll concentration was found with increasing salinity for both the species. Total chlorophyll concentration halved for both the species as the salinity was increased from 0 to 35 ppt (0.34 to 0.17 mg/g for H. fomes and 0.07 to 0.03 mg/g for X. moluccensis). In addition, the H. fomes leaves have five times more chlorophyll concentration than X. moluccensis. Proline accumulation in leaves of X. moluccensis was found considerably high compared to H. fomes and increase with salinity for both the species. It was quadrapoled (254 to 1462 µmoles/g) in X. moluccensis and doubled (8 to 16 µmoles/g) in H. fomes. Seedling survival was found to vary with species and salinity levels. Survival of H. fomes seedlings decreased from 83% to 58% at 15 to 35 ppt salinity and no mortality was observed at lower salinities of 0 to 10 ppt. In contrast no mortality was observed from 0 to 25 ppt salinity in X. moluccensis seedlings and 92% seedling survived at 30 and 35 ppt salinities. Both the species showed lower biomass accumulation at higher salinities. Higher biomass increment (38 to 52%) was observed for X. moluccensis than that of H. fomes(33%) at lower salinities (0 to 5 ppt) and reduced gradually at higher salinities. This study revealed that X. moluccensis is more salt tolerant than H. fomes considering higher survival as a result of high proline accumulation in leaves that helps to overcome salt induced negative osmotic pressure. But growth is reduced due to lowering of chlorophyll accumulation at higher salinities for both the species.

Using Continuous Change Detection and Classification of Landsat Data to Investigate Long-Term Mangrove Dynamics in the Sundarbans Region

Mangrove forests play a global role in providing ecosystem goods and services in addition to acting as carbon sinks, and are particularly vulnerable to climate change effects such as rising sea levels and increased salinity. For this reason, accurate long-term monitoring of mangrove ecosystems is vital. However, these ecosystems are extremely dynamic and data frequency is often reduced by cloud cover. The Continuous Change Detection and Classification (CCDC) method has the potential to overcome this by utilising every available observation on a per-pixel basis to build stable season-trend models of the underlying phenology. These models can then be used for land cover classification and to determine greening and browning trends. To demonstrate the utility of this approach, CCDC was applied to a 30-year time series of Landsat data covering an area of mangrove forest known as the Sundarbans. Spanning the delta formed by the confluence of the Ganges, Brahmaputra and Meghna river systems, the Sundarbans is the largest contiguous mangrove forest in the world. CCDC achieved an overall classification accuracy of 94.5% with a 99% confidence of being between 94.2% and 94.8%. Results showed that while mangrove extent in the Sundarbans has remained stable, around 25% of the area experienced an overall negative trend, probably due to the effect of die-back on Heritiera fomes. In addition, dates and magnitudes of change derived from CCDC were used to investigate damage and recovery from a major cyclone; 11% of the Sundarbans was found to have been affected by Cyclone Sidr in 2007, 47.6% of which had not recovered by mid-2018. The results indicate that while the Sundarbans forest is resilient to cyclone events, the long-term degrading effects of climate change could reduce this resilience to critical levels. The proposed methodology, while computationally expensive, also offers means by which the full Landsat archive can be analyzed and interpreted and should be considered for global application to mangrove monitoring.