Estimating carbon stocks and woody perennials diversity in cropland agroforestry on three different land ecosystems in Bangladesh

Abstract

Background

Cropland agroforestry practices are widely adopted over various land ecosystems in Bangladesh, offering the potential to capture carbon (C) and safeguard biodiversity. Lack of accurate assessments of biomass carbon and the diversity of woody perennials in cropland agroforestry practices across different land ecosystems presents a hurdle for the efficient execution of initiatives such as REDD + and comparable mechanisms. The present research sought to estimate biomass carbon stocks and diversity of woody species, exploring the influence of stand structure and diversity indices on these C stocks. We conducted woody perennials’ inventory in 180 sampling quadrates (10 m × 10 m) from cropland agroforestry practices in forest, plains land, and char land ecosystems.

Results

Altogether, we identified 42 woody species; however, the predominant species in three land ecosystems were Acacia auriculiformis, Gmelina arborea, and Tectona grandis. Swietenia macrophylla and Swietenia mahogany contributed the greatest amount of carbon stocks. Carbon stocks in woody perennials were 30–44% higher in plains land and forest land ecosystems compared to the char land ecosystem, attributable to significantly increased stand density, basal area and diameter. The significantly highest Shannon–Wiener index (2.75) and Margalef’s richness index (3.37) were found in forest land compared to other ecosystems. The highest total carbon stocks (131.27 Mg C ha⁻¹) of cropland agroforestry were found in the forest land ecosystem, which had the greatest soil organic carbon, density, and richness of woody perennials. A rise in the richness and diversity index of woody species by one unit led to a concurrent increase of 12 and 8 Mg C ha⁻¹ in carbon stocks, respectively.

Conclusions

Cropland agroforestry practices in the forest land ecosystem are more diverse and could sequester more carbon stock than in the other two land ecosystems in Bangladesh. The biomass C stocks of woody species were positively correlated with stand structure and diversity, having the potential to contribute to biodiversity conservation in Bangladesh and other similar countries.