Biomass accumulation and carbon stocks of soil and tree components of different agroforestry systems in tropical moist regions of Bangladesh

Abstract

The increase in greenhouse gases has made global warming, the most pressing environmental challenge requiring prompt action. Agroforestry is globally recognized to mitigate this problem due to its significant potential to capture atmospheric carbon dioxide and provide various ecosystems benefits including food security. However, very few studies have been conducted on estimating biomass accumulation and carbon (C) stock in different agroforestry systems in the tropical moist climatic regions of Bangladesh. The current study was carried out to evaluate the biomass accumulation and C stock under four different agroforestry systems: Timber tree-based agroforestry system (TAS), fruit tree-based agroforestry system (FAS), medicinal plant-based agroforestry system (MPAS), and mixed tree-based agroforestry system (MAS) under tropical moist climatic conditions in Madhupur, Bangladesh. The sites and types of the agroforestry systems were selected based on dominance and accessibility. A total of 108 plots (10 m × 10 m) were randomly selected for data collection viz. plant density, height and diameter of the tree species, and collection of soil samples. A nondestructive sampling method followed by allometric equations was used to determine the biomass of the tree species. Overall, 216 Soil samples from two layers (0–15 cm and 15–30 cm depths) were also collected from randomly selected points to determine soil bulk density and soil organic carbon (SOC). The data was collected in four agroforestry systems: TAS, FAS, MPAS, and MAS with the plant density of 678, 611, 633 and 722 trees ha^-1 respectively. Results showed that tree C stock among the four agroforestry systems was significantly different, with a maximum stock of 226.05 t ha^-1 in MAS, and it was 29.99 %, 37.92 % and 54.81 % greater than the carbon stock of TAS, MPAS, and FAS, respectively. The highest SOC was estimated (51.22 t ha^-1) in MAS, at 0–30 cm depth followed by 42.37 t ha^-1, 41.00 t ha^-1, and 37.53 t ha^-1 for TAS, MPAS, and FAS, respectively. Similarly, the amount of total carbon stock (C stock of trees and SOC) of the agroforestry systems was found in the order of MAS > TAS > MPAS > FAS. The results suggested that MAS, with the highest biomass accumulation and C storage are the most effective agroforestry systems compared to the others in requisites of environmental benefits particularly in carbon storage.