Arafat Rahman
Department of Soil, Water and Environment, University of Dhaka, Dhaka 1000, Bangladesh
MJ Uddin
Department of Soil, Water and Environment, University of Dhaka, Dhaka 1000, Bangladesh
Md Raisuddin Sikder
Department of Soil, Water and Environment, University of Dhaka, Dhaka 1000, Bangladesh
Humyra B Murshed
Department of Soil, Water and Environment, University of Dhaka, Dhaka 1000, Bangladesh
JA Faysal
Department of Soil, Water and Environment, University of Dhaka, Dhaka 1000, Bangladesh
Mohiyuddeen Ahmad
Department of Soil, Water and Environment, University of Dhaka, Dhaka 1000, Bangladesh
ASM Mohiuddin
Department of Soil, Water and Environment, University of Dhaka, Dhaka 1000, Bangladesh
Lalmai hill ecosystem, Toposequence, Soil properties, Carbon stock
Lalmai hill ecosystem of Bangladesh
Crop-Soil-Water Management
Soil Physical Properties
The Lalmai hills lie between 23°20' to 23°30' North latitude and 91°05' E to 91°10' East longitudes. This area is bordered on the east by the Tripura hills of India, particularly the Raghunandan hill; on the west by the Meghna River; on the north by the Gumti River; and on the south-southeast by the Dakatia River(14). The land use and the land cover are very diverse in the study sites. It was reported(15) the predominant flora species include Sal (Shorea robusta), Jackfruit (Artocarpus heterophyllus), Taal (Borassus flabellifer), and Kadam tree (Neolamarckia cadamba), etc. On the other hand, a variety of shrubs and herbs were also reported, viz. Bhant (Clerodendrum viscosum), Assam lata (Mikania scandens), Sothi (Curcuma zeodaria), Motkila (Glycosmis arborea) etc. The topography of the Lalmai hills consists of hillocks, floodplains, rivers, etc., and are located along with the central arcuate bulge of the westernmost part of the Chittagong-Tripura Fold Belt (CTFB) of the Bengal foredeep(14). It is reported that CTFB formed due to the still-ongoing collision between the Indian plate and the Burmese plate and exposing the Miocene to Recent deposits(16,17). The nature of the parent material is unconsolidated to semi-consolidated clay, silty clay, silt, and sands(14). Forty-five soil samples covering nine soil profiles were selected to conduct the present study. Four soil profiles, e.g., Lalmai series (Typic Endoaquepts), Khadimnagar series (Typic Endoaquents), Shalbon series (Aeric Endoaquepts), and Kharera soil series belongs to hill formation. It is reported that the Lalmai series, Khadimnagar series, Shalbon series belongs to Dupi Tila hill formation and whereas Kharera series (Typic Endoaquepts) belongs to Pleistocene piedmont deposits over Dihing formation; Pritimpasha series (Aeric Dystrudepts), Mano series (Aeric Dystrudepts) and Chakla series (Vertic Endoaquepts) belongs to North-eastern piedmont alluvium; Chandina series (Typic Dystrudepts/ Typic Endoaquepts) and Debidwar series (Typic Dystrudepts) belongs to Meghna estuarine alluvium(18). During field visit and sampling, Global positioning systems (GPS) was used to identify the geo-coordinates and elevation of the sampling sites. Soil drainage and soil textural class were assessed using appropriate field guides. The elevation of the sampling points was also verified from the raster data of the digital elevation model (DEM) using ArcGIS 10.3. Soil samples were collected at five different depths of 0-20, 20-40, 40-60, 60-80, and 80-100 cm intervals from each pit of the study sites. Using fixed depth (1 meter) of the soil profile, the sampling was performed in toposequence arrangements. Soil samples from each pit/profile were collected in thick polythene bags. The samples were air-dried, ground, and sieved through 2 mm and 0.5 mm sieve, respectively, and mixed thoroughly. The samples were then preserved in plastic containers for laboratory analysis. Soil pH was determined in soil-water suspension using a precalibrated pH meter(19). SOC was determined by following the method of Walkley and Black(20) and the Kjeldahl method(21) was used for total soil nitrogen (TSN) determination. The particle size analysis of soils was carried out by the hydrometer method(22). Soil bulk density was determined by using the core method(23). The cation exchange capacity of soils was determined by 1N ammonium acetate (24). It may be noted that the bulk density and SOC concentration (%) are the two prerequisites for estimating SOC stock or storage. SOC storage was calculated using the following equations(9,25,26). Total soil organic carbon (TSOC) = SOCi × BDi × Di; Where SOCi is the SOC content in the ith layer (g/kg soil), BDi is the bulk density in the ith layer (g/cc), and Di represents the thickness of the ith layer (cm).
Dhaka Univ. J. Biol. Sci. 30(2): 331-343, 2021 (July)
Journal