Multiple drivers of tree and soil carbon stock in the tropical forest ecosystems of Bangladesh

Tropical forest ecosystem act as a carbon sink and plays a vital role in climate change mitigation. The carbon storage capacity of tropical forest ecosystems is declining gradually in recent years. But studies regarding the multiple drivers of tree and soil carbon in the tropical forest ecosystems are scarce. Our study aims to quantify the tree and soil carbon storage capacity and to explore how these carbon storages are associated with both biotic (stand structure, anthropogenic disturbance) and abiotic drivers (climate, topography, and soil) simultaneously in tropical forest ecosystems. The present study was conducted in two forest-protected areas of Bangladesh, namely- Satchari National Park (SNP), and Khadimnagar National Park (KNP). Results showed that tree carbon stock was 72.9 t ha(-1) and 58.2 t ha(-1) in SNP and KNP, respectively. Besides, soil carbon was 77.1 t ha(-1) in SNP and 130.5 t ha(-1) in KNP. We found that tree carbon was positively correlated with all stand structure parameters. However, soil carbon was negatively correlated with tree richness, height, and basal area. Anthropogenic disturbance had a negative correlation with tree carbon and a positive correlation with soil carbon stock. No significant correlation was observed between tree carbon and local climatic parameters. But soil carbon had a positive correlation with annual precipitation and a negative correlation with annual mean temperature. Furthermore, tree carbon was positively associated with elevation and slope whereas soil carbon was negatively associated with elevation. Tree carbon was negatively correlated with silt% but positively with sand%. Conversely, soil carbon showed significant positive associations with soil moisture, bulk density, soil pH, and soil silt%. Our study provides a comprehensive insight on the understandings of key drivers of tree and soil carbon storage in the tropical forest ecosystem of Bangladesh. We concluded that anthropogenic disturbance and stand characteristics regulate tree carbon stock while soil carbon is mainly associated with local climate and soil properties in the studied tropical forest ecosystems.