Carbon stocks of homestead forests have a mitigation potential to climate change in Bangladesh

A total of 176 homestead forests at three altitudes in the Chittagong Hill Tracts, Bangladesh were randomly surveyed to estimate carbon (C) stocks and how stand structure affects the biomass C. All woody vegetations were measured, and litter and soil (0–30 cm depth) were sampled. The tree biomass C stock in the top two altitude forests was up to 37–48% higher than in low altitude, owing to significantly higher tree density and species diversity. An increase in species diversity index by one unit increased the biomass stock by 23 Mg C ha−1. The C stock of litterfall in low altitude forests was 22–28% higher than in the top two altitude due to the deposition of litters downslope and deliberate use of mulch for soil improvement and conservation, resulting in up to 5% higher total soil C. The topsoil C was 10–25% higher than the deeper soil, depending on the altitude. The forest stored 89 Mg C ha−1, indicating a potential for C sequestration in trees outside forest. This study would help policymakers to strengthen the recognition of small-scale forests for mitigation in REDD + (reducing emissions from deforestation and forest degradation, the role of conservation, sustainable management of forests, and enhancement of forest carbon stocks) and support owners through C credits from sustainably managed forests.

Effects of tree species diversity and stand structure on carbon stocks of homestead forests in Maheshkhali Island, Southern Bangladesh

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, and Artocarpus heterophyllus stored 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−1 in 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.

Effects of Tree Species Diversity and Stand Structure on Carbon Stocks of Homestead Forests in Maheshkhali Island, Southern Bangladesh

BackgroundThis study aimed to estimate the carbon (C) stocks in homestead forest ecosystems (trees, litterfall, and soil) of Maheshkhali Island in Bangladesh and how tree species diversity and stand structural variation affected these C stocks. We randomly surveyed a total of 239 homestead forests proportionately allocating in hillside (67), beachside (69), and inland (103) in 2019 for measuring woody plants and sampling litterfall and C in soil at 0-30 cm depth. Tree (above- and below-ground) biomass was estimated by using pan-tropical allometric equations, and carbon of litterfall and soil were analyzed in a laboratory. ResultsWe found a total of 52 tree species, of which, 41, 42, and 48 species were in the hillside, beachside, and inland, respectively, corresponding to the individuals of 840, 540, and 1504 sampled. According to the results, species diversity, richness, stand density, basal area (BA), and tree diameter at breast height (DBH) and height were significantly (p ≤ 0.05) greater in the hillside and inland homestead forests, compared to the beachside. Most abundant species, for example, Mangifera indica, Samanea saman, and Artocarpus heterophyllus in the inland and hillside homestead forests stored most C in biomass, compared to the beachside forest. Tree biomass C stocks were 48-67% greater in the inland and hillside than on beachside forests due to significantly (p ≤ 0.05) greater stand density, BA, and DBH. The overall C stock of litterfall was 0.1% of the total biomass carbon. C stock in soil surface was greatest in the hillside homestead forests due to the greatest litterfall. The total soil C stock was also affected by tree species, stand density and species richness, and their interaction with soil properties. Total soil C stocks across the depths were greatest (51 Mg ha-1) in the inland homestead forests, with the greatest stand density and species richness. ConclusionsHomestead forest ecosystems across the area stored total 96 Mg C ha-1, which thus can contribute to climate change mitigation while generating C credit for small-scale homestead forests owners as well as conserving biodiversity in Bangladesh and countries alike.