Unveiling tree diversity and carbon density of homegarden in the Thodupuzha urban region of Kerala, India: a contribution towards urban sustainability

The present study aimed to assess the role of homegarden (HG) in safeguarding the tree diversity and carbon (C) density or storage in the Thodupuza urban region of Idukki district in Kerala, India. A stratified random approach was used for selecting the four homegardens (HGs) with a size of 1hectare (ha). The study mainly focused on species richness, diversity, above ground biomass, carbon, correlation and distribution of carbon with various variables, species and group wise carbon storage of the system. A total of 992 trees from 66 species belonging to 31 families were enumerated with representation of 4 endemic, 1 vulnerable, 1 endangered and 23 exotics. The diversity indices obtained were closer to those of the forest ecosystem. Above ground biomass and carbon density were estimated to be 67.06 t/ha (tonne/hectare) and 31.85 6 t/ha respectively. Species Tectona grandis showed dominancy in carbon and Important Value Index. Correlation analysis among species revealed that carbon exhibited a strong positive trend with basal area and tree density, but in the case of plot (HG)-wise examination only basal area had a strong positive relationship. The diametric class analysis showed skewed type of distribution for carbon and tree density while diversity had reverse j-shaped curve. Among the two plant groups, cultivated species had an edge over native in storing carbon. Overall, this assessment shows the potential of using homegardens as a socio-ecological systems for sustainable development particularly in terms of land availability and climate mitigation options in the face of rapid urbanization.