Population structure and carbon storage of critically endangered tree Karomia gigas (Faden) Verdic in the coastal forests of Lindi, Tanzania

Abstract

Global biological loss is predominantly propelled by human activities resulting in the extinction of some important plant species while pushing others to the brink of critical danger. Better understanding of the ecology of these important species facilitates safeguarding their habitats and the development of sustainable restoration strategies. Data on vegetation, physiographic, edaphic and anthropogenic variables were collected from forty (40) concentric temporary circular plots in two forest reserves (i.e. Mitundumbea and Litipo Forest Reserves) to determine population structure and above-ground carbon storage of Karomia gigas (Faden) Verdic a critically endangered tree species in the coastal forests of Lindi, Tanzania. Within the Litipo Forest Reserve, we recorded a total of 30 K. gigas individual trees, comprising 13 seedlings, 10 saplings and 7 mature trees. The largest measured diameter at breast height (dbh) in this forest was 29.2 cm while the smallest was 0.9 cm. In contrast, the Mitundumbea Forest Reserve had 15 mature K. gigas individual trees but lacked seedlings and saplings. The largest dbh recorded in this forest stood at 59.7 cm, with the smallest dbh measurement being 5.1 cm. We overall observed significant negative correlations between the abundance of K. gigas adults and both soil organic carbon (P = 0.005) and burnt areas (P = 0.003). The total abundance of K. gigas showed a negative association with soil organic carbon (P = 0.011). Furthermore, the carbon storage of K. gigas exhibited a negative relationship with burnt areas (P = 0.005) and a positive relationship with elevation (P = 0.016). None of the assessed physiographic, edaphic, and anthropogenic variables could explain the overall abundance of K. gigas seedlings and saplings. The average above-ground carbon stored by K. gigas in Litipo forest was 3.19 ± 0.72 t ha−1, while in Mitundumbea it was 12.76 ± 1.75 t ha−1. To increase the population size and restore this once-extinct tree species, anthropogenic fires must be controlled for plant diversity conservation and environmental sustainability.