Mirza Asadul Kibriya
Department of Environment, Paribesh Bhaban, E/16, Agargaon, Sher-E-Bangla Nagar, Dhaka 1207, Bangladesh
Sanjoy Saha*
Centre for Integrated Studies on the Sundarbans (CISS), Khulna University, Khulna 9208, Bangladesh
Mohammad Raqibul Hasan Siddique
Forestry and Wood Technology Discipline, Khulna University, Khulna 9208, Bangladesh
Mahmood Hossain
Forestry and Wood Technology Discipline, Khulna University, Khulna 9208, Bangladesh
Leaching, Mass loss, Nutrient cycling, Shorea robusta
Madhupur Sal Forest of Bangladesh
Crop-Soil-Water Management
Nutrient status, Leaf litter, Madhupur sal forest
Leaf litter selection and leaching experiment: Bulk of freshly fallen senescent leaves of S. robusta were collected from Modhupur Sal forest of Tangail district during dry season (February) when the maximum leaf fall took place. Litter was air-dried at room temperature for a week. The air-dried leaves were mixed thoroughly and a total of 33 samples of 5 gm each were prepared. Each sample was placed at room temperature into individual beaker (500 ml) and 200 ml of distilled water was poured in each beaker and few drops (0.2-0.3 ml) of HgCl2 solution (50 mg l-1) (McLachlan, 1971; Otsuki & Wetzel, 1974) were added in each beaker to prevent fungal decay. Three samples were kept in an oven at 80 °C until constant weight to obtain the air-dry to oven-dry conversion weight.
Sample collection and measurement: Three replicates of samples were collected at 1, 2, 3, 6, 12, 24, 48, 72, 120 and 192 hours of intervals and the collected samples were rinsed by distilled water and oven-dried at 80 °C to constant weight. The mass loss (%) due to the leaching was calculated from the differences between initial and final oven-dried weights and was expressed as a percentage of initial weight. The rate of mass loss was obtained by dividing mass lost (%) with the leaching time. Conductivity (μS cm-1), total dissolved solid (mg L-1) of leached water sample were measured by a conductivity and TDS meter (Ciba-Corning Diagnostic Ltd., England).
Nutrients measurement in leaf litter: The leaf samples were processed and acid digested according to Allen (1974). Nitrogen (N) and phosphorus (P) concentration in sample extracts were measured according to Weather burm (1967) and Timothy et al., (1984), respectively using UV-Visible Recording Spectrophotometer (Shimadzu UV-160A, Japan). Potassium (K) concentration in leaf extracts at different time intervals were measured by Flame photometer (PFP7, Jenway LTD, England). The nutrient amounts released from leaf litters were calculated as differences between initial and final absolute amounts and also expressed as a percentage of the initial value.
Statistical analysis: The rate of mass loss and nutrients (N, P and K) concentration in leaf litter of each species at different time intervals was compared by one-way ANOVA analysis followed by Duncan Multiple Range Test (DMRT) of variance using SAS 6.12 statistical software.
Estimation of leaf litter and leaf litter standing crop: Estimation of leaf litter production was conducted during the peak litter fall time in the Modhupur forest of Tangail District using temporary sample plots (litter trap) of 2 m x 2 m. The leaf litter inside the traps were collected daily (24 hours’ interval) for 15 days and oven-dried at 80 °C until constant weight. Moreover, twenty temporary sample plots of 2 m x 2 m were set randomly on the forest floor to estimate the leaf litter standing crops.
Quantification of leached nutrients: Amount of leaf litter standing crop was calculated as area basis. The initial and final nutrients (N, P and K) concentration will be multiplied with the total amount of leaf litter standing crop to get the harvestable amount of leaching nutrients.
Khulna University Studies Volume 16(1 & 2): 1-8 : 2019
Journal