Background: The homestead forests of Bangladesh occupy 0.27 million hectares (10% of the total forested area) and have potential to store carbon (C) and conserve biodiversity. Small scale forestry practices, however, are lacking reliable estimation of C stocks and tree species diversity. This may hinder successful implementation of REDD + and similar mechanisms as they concentrate on large-scale forests. This study aimed to estimate the above- and below-ground carbon stocks in homestead forests of Maheshkhali Island in Bangladesh and how tree species diversity and stand structural variation affect these C stocks. We randomly surveyed a total of 239 homestead forests in the hillside, beachside, and inland in 2019.Results: Tree biomass C stocks were 48–67% greater in the inland and hillside forests than in the beachside due to significantly greater stand density, basal area, tree diameter. In total we found 52 tree species, but most abundant species in the inland and hillside forests,Mangifera indica,Samanea saman, andArtocarpus heterophyllusstored the most C in tree biomass. Greater tree species richness and diversity index in the inland and hillside forests indicated greater above- and below-ground tree biomass C stocks. An increase in tree species richness and diversity index by one unit was found to increase the tree biomass C stock by 22 and 30 Mg C ha⁻¹, respectively. The total soil C stock was also affected by tree species diversity, stand density, and their interaction with soil properties. Total soil C stocks were greatest (51 Mg ha⁻¹) in the inland forests, having also the greatest stand density and tree species richness. C stock in soil surface was greatest in the hillside forests due to the greatest litterfall, but the average share of litterfall from the total biomass C was only 0.1%.Conclusions: Homestead forest ecosystems could store 96 Mg C ha⁻¹in total, which can contribute to climate change mitigation by generating C credits for small-scale homestead forests owners. Above- and below-ground tree biomass C stocks were found to correlate with tree species diversity, which may also contribute to biodiversity conservation in the REDD + in Bangladesh and countries alike.

The impacts of alternative forest management scenarios and harvest intensities on climate change mitigation potential of forest biomass production, utilization and economic profitability of biomass production were studied in three boreal sub-regions in Finland over a 40-year period. Ecosystem modelling and life cycle assessment tools were used to calculate the mitigation potential in substituting fossil materials and energy, expressed as the net CO₂ exchange. Currently recommended management targeting to timber production acted as a baseline management. Alternative management included maintaining 20% higher or lower stocking in forests and final felling made at lower breast height diameter than used in the baseline. In alternative management scenarios, logging residues and logging residues with coarse roots and stumps were harvested in final felling in addition to timber. The net CO₂ exchange in the southern and eastern sub-regions was higher compared to the western one due to higher net ecosystem CO₂ exchange (NEE) over the study period. Maintaining higher stocking with earlier final felling and intensified biomass harvest appeared to be the best option to increase both climate benefits and economic returns. Trade-offs between the highest net CO₂ exchange and economic profitability of biomass production existed. The use of alternative displacement factors largely affected the mitigation potential of forest biomass.