Tropical forests of Bangladesh are facing rapid loss in floristic diversity and resultant changes of vegetation necessitates the assessment of plant composition and diversity. The present study was conducted to assess the composition of native tree species of Rampahar Forest Reserve of Rangamati hill district, Bangladesh. Rampahar is a remnant tropical semievergreen natural forest extending to an area of 648 ha. Simple random sampling method with 20 m × 20 m sized 20 and 5 m × 5 m sized 10 samples plots were used to study both tree species composition and seedling status of tree species. A total of 50 tree species under 28 families and 15 regenerating tree species under 13 families were recorded in the study area. Family Moraceae possessed the highest number of tree species (6 species) while families Anacardiaceae and Sterculiaceae possessed the highest number (2 species) for regenerating tree species. The survey indicated that Protium serratum (Wall. ex Colebr.) Engl. is the most dominant tree species with the highest relative density (RD), relative frequency (RF) and importance value index (IVI). Basal area of all the tree species was 13.13 m 2 /ha where Ficus religiosa was represented by the highest basal area (1.14 m 2 /ha). Protium serratum was also a dominant regenerating tree species with highest RD (15.24%), RF (16.30%) and IVI (50.09). The native trees species of this remnant forest need attention for immediate conservation programs to prevent further degradation of the forest.
The Deccan Volcanic Province of India is considered as one of the largest basalts-covered regions in the world, formed due to extensive outpouring of basaltic lavas during Deccan volcanism (∼65 Ma). The sedimentary sequence below the flood basalt is mainly characterized by Mesozoic strata with a varying thickness of 1000 m to 2500 m. It is considered that requisite heat generation due to Deccan Trap volcanism soon after the Cretaceous sedimentation may have acted as a catalyst in hydrocarbon potential in this area (Vardhan et al. 2008). However, it is essentially unexplored because of the limitations of conventional marine streamer P-wave seismic acquisition in imaging the structures both intra-basalt and sub-basalt. The major challenges can be considered as follows: Strong reflections due to high impedance contrasts at the top (and bottom) of the basalts leading to significant loss of transmitted seismic energy; Scattering of energy due to large acoustic impedance contrast at top and bottom of the basalt; Generation of multiples, both surface-related and interbed, from the top and bottom of the basalt, and intra-basalt boundaries, masking genuine primary reflections at the pre-basasediments; Significant attenuation of seismic energy in the basaltic sequences due to its complex internal structure generally causing weak sub-basasignal; Low signal-to-noise ratio creating ambiguity in estimating accurate velocity model of subsurface. This case study demonstrates that, even with legacy marine streamer surveys, an appropriate workflow of combining suitable advanced technologies can help to overcome the long-standing challenges of sub-basalt imaging. The reprocessed data show clear uplift in the sub-basalt imaging and the inversion results validate the quality of the new data in relation to the well logs.
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