Carbon stock and woody species diversity patterns in church forests along church age gradient in Addis Ababa, Ethiopia

Most of the Ethiopian Orthodox Churches comprise natural and planted forests and trees on their premises. A study was conducted to investigate carbon stock and woody species diversity patterns along the church age gradient in Addis Ababa city. We hypothesized that the carbon stock would relate to the church age gradient. Thus, the study was conducted in forests belonging to churches that were selected in a stratified random sampling from four age categories with the year of establishments ranging from 1897 to 1993. Counting of all the woody species and DBH and height measurement of all individuals with DBH of 5 cm and above was carried out. Carbon stock and different diversity indices were computed, and the relationships between church age and tree parameters were evaluated. Results showed that the forests were characteristically small (0.6 +/- 0.57 ha), and the tree species with the highest total carbon stock were Juniperus procera, Eucalyptus globulus and E. camaldulensis. The mean amount of carbon stock contained in each church forest was 156 +/- 92 t ha-1. A total of 50 indigenous and 40 exotic woody species were identified. A statistically significant difference (p < 0.05) among the four Strata was revealed for the carbon stock of native trees. Correlation analysis also revealed a significant positive relationship between church age and native trees' carbon stock. We conclude that the church forests have a very important role in carbon sequestration and biodiversity conservation, and thus scaling up the long-term maintenance and management of such small-sized forests in urban green spaces is vital.