Showing papers on "Heritiera fomes published in 2019"

Effects of nutrient limitation, salinity increase, and associated stressors on mangrove forest cover, structure, and zonation across Indian Sundarbans

Abstract: Anthropogenic coastal activities and natural stressors aggravate degradation of small coastal patches of mangroves, which in turn destroy local resilience of mangrove forests in the Indian Sundarbans, the continuous mangrove habitat that spans between India and Bangladesh. We conducted an analytical survey across 19 shoreline mangrove fringes spanning the Sundarbans, including both healthy and disturbed forests, and evaluated ninety-five 60-cm composite sediment cores across a degradation and salinity gradient from ~ 4 to ~ 12 ppt. Increased salinity and anoxicity greatly inhibited nutrient cycling and release by microbial decomposers, subsequently resulting in nutrient-poor soil as a condition of degradation. Nutrient limitation, salinity rise, anoxicity increase, and sulfide build-up negatively controlled forest structure causing declines of forest coverage from ~ 98 to ~ 11%. In addition, the tide-dominated salinity gradient controlling species zonation was disrupted in disturbed forests with salinity-sensitive species gradually disappearing. An obvious change in species distribution is anticipated while salt-sensitive Heritiera fomes, Xylocarpus spp., and Phoenix paludosa failed to cope with increased salinity, evident by their absence from many forests. Excoecaria agallocha and Avicennia spp. acclimated well and expanded freely into degraded forests across the Sundarbans. Overall, our study strongly establishes salinity intrusion as primary mechanism for mangrove degradation.

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

Abstract: 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.

Comparison of calorific values and ash content for different woody biomass components of six mangrove species of Bangladesh Sundarbans

Abstract: The study of calorific values of mangrove plants is valuable indices for reflecting the energy conversion and material flow of the forest ecosystem. In this study, the calorific value and ash content of different biomass components, i.e. leaf, bark, sapwood and heartwood of six important mangrove species, namely goran (Ceriops decandra Griff. W. Theob.), keora (Sonneratia apetala Buch.-Ham.), passur (Xylocarpus mekongensis Pierre), sundri (Heritiera fomes Buch.-Ham.), gewa (Excoecaria agallocha L.) and jhana garjan (Rhizophora mucronata Lam.) of Bangladesh were evaluated. The gross calorific values (GCVs) and ash-free calorific values (AFCVs) of different biomass components of six species were in the range of 14.15–19.18 MJ/kg and 14.90–19.37 MJ/kg, respectively. Heartwood of H. fomes showed the highest GCV and AFCV among all of the mangrove species. The highest ash content (AC) was found for the bark of X. mekongensis (6.7%), while S. apetala sapwood and H. fomes bark showed the lowest AC (0.5%). The GCVs, AFCVs and ACs of different woody biomass components of six mangrove species were significantly different. The fuel value index (FVI) of heartwood and sapwood of six mangrove species was ranged between 1.34 for E. agallocha heartwood and 7.15 for H. fomes heartwood. The findings of this study are important for selecting the suitable fuelwood species for higher fuel value from and around the biggest single tract mangrove forest, the Sundarbans.

Effect of NPK fertilizers on seedling growth of mangrove species

Abstract: An experiment was conducted to assess the effect of NPK fertilizers on seedling growth and survival of five important mangrove species of Bangladesh for nine months. Seedlings were raised in the nursery using plastic pots. NPK fertilizers with three treatments (control, 4 gm and 8 gm doses) were used two times when seedlings age was 3 and 6 months. The result showed that seedlings height growth of Excoecaria agallocha was enhanced significantly with the application of NPK fertilizers but it was shown negatively significant effect on height growth of Xylocarpus mekongensis after second time fertilizer application. Moreover, NPK application enhanced mortality of Avicennia officinalis and Ceriops decandra seedlings in both times of fertilizer application. But no effect of NPK fertilizers on seedlings growth and survival of Heritiera fomes were observed.

Invasive Species in the Sundarbans Coastal Zone (Bangladesh) in Times of Climate Change: Chances and Threats

Abstract: The Sundarbans mangrove forests, wetlands and their native as well as invasive plant species are lying within the Bangladesh coastal region, which is gifted with vast natural resources, a delta, tidal flat, mangrove forests, marches, lagoons, bars, spilt, estuaries and coastal ecological environment. These habitats, biotopes and ecosystems also serve as habitat for especially four dominant tree species of the Sundarbans, the Sundri (Heritiera fomes), Gewa (Excoecaria agallocha), (Ceriops decandra) and (Sonneratia apetala). But the existence of these and many more native species is endangered. The Sundarbans species are threatened by various natural and anthropogenic pressures including climate change. So the native species are approximately decreasing significantly by the year 2100 due to sea level rise (88 cm) in the Sundarbans area compared to the year 2001.There 23 invasive species, which belong to 18 families and 23 genera. These species are highly invasive, six species are moderately invasive and the remaining are potentially invasive. From the 23 invasive species only four are exotic or alien. The disturbances may arrest succession at any stage and contribute to the biological invasion of invasive plants. The within these biodiversity hotspots and vast natural or coastal water resources lying potential for communities survival and 36.8 million dependent people are some of the strongly pending managing demands next to existing Natural World Heritage Sites’ already existing protective management support to be discussed in this chapter. As with the coastal natural resources drastically reduction due to unplanned use by community and stakeholders, also the Sundarbans mangrove forests, wetlands and their species are vastly affected through these developments and the most important observation for vulnerability aspects and maximum possible amplitudes is coming up, which has been investigated in within this research and chapter. Also the present situation stated that an integrated natural resource management plan is necessary for the protection of the mangrove coastal ecosystem.

Species Distribution in Different Ecological Zones and Conservation Strategy of Halophytes of Sundarbans Mangrove Forest of Bangladesh

Abstract: Species distribution of halophytes and their conditions in different ecological zones of Sundarbans mangrove forest were evaluated. Water flow within the rivers of the Sundarbans mangrove forest and seasonal variation of water salinity of the rivers were discussed. Highest salinity (electrical conductivity) 27,500 micromhos/cm (Polyhaline zone) and 5800 micromhos/cm (Oligohaline zone) was observed in April; and lowest salinity was 10,150 micromhos/cm (Polyhaline zone, July) and 500 micromhos/cm (Oligohaline zone, July). Environmental constraints and ecophysiological response in relation to soil environment and plant and plant roots in relation to salinity were highlighted. Surface soil of this halophytic forest is silty clay loam; soil pH ranges from 6.9 to 7.5; calcium is the dominant cation and is highest in the Oligohaline zone followed by Mesohaline and Polyhaline zones. The respiratory roots (pneumatophores) of various forms (such as peg like, knee root, buttress roots, stilt roots) in different species were described. Measurement of redox potential in soils from selected places showed low values particularly in the Oligohaline zone (+60 mV, where the Heritiera fomes plant shows top dying) followed by Mesohaline and Polyhaline zone. Low oxidation-reduction potentials (anaerobiosis) may be one of the factors responsible for the cause of top dying, and these properties influence plant growth and distribution. Highest soil salinity (6950 micromhos/cm) was in the Polyhaline zone, and in the Oligohaline zone, highest salinity was 650 micromhos/cm. The vegetation pattern is given based on field observation, with the dominant species; and associated species are placed in relation to density and abundance. Comparison of species composition (large and small trees, shrubs, herbs, palms, fern, lichen and climbers) and their condition in the three ecological zones showed the nature of their distribution pattern. Plant association and distribution of halophyte species in relation to salinity in different ecological zones indicated their nature of distribution. Anthropogenic and natural threats to the halophytic mangrove species and their conservation are discussed. Research for mangrove conservation in relation to stress ecology and rehabilitation of mangrove halophytes, linkage between the structure of mangroves and ecosystem services and future of mangrove halophytes were highlighted.