WOODY SPECIES DIVERSITY AND CARBON STOCK VARIATION ALONG ALTITUDINAL GRADIENTS AT MUHABURA VOLCANO, NORTHERN RWANDA

This study was conducted at Muhabura Volcano, in Volcanoes National Park, Northern Rwanda, to determine woody species diversity and carbon stock potential of woody species along altitudinal gradients. The study area was stratified into three strata based on physical appearance of vegetation and elevation gradients: low altitude 2502-2882 m a.s.l, middle altitude which lies between 2883-3109 m a.s.l and upper altitude which lies between 3110-4127 m a.s.l. A total of 60 plots of 20m x20m with 4 transect lines were used to collect information on woody species structure and composition, litter and soil in three altitudinal gradients. A total of 21 woody species that belonged to 16 families were identified. The overall species richness, Shannon wiener, Simpson, evenness and similarity indices values of the entire study area were 21, 2.46,0.46,0.65 and 0.38 respectively. The results of the study showed that the woody species diversity at low altitude was considerably more with even distribution while that of middle altitude was less diverse and dominated by few species. The most dominant species in the low altitude is Hagenia abyssinica (23%), the middle altitude presents Erica arborea (77%). There was no woody species with DBH greater or equal to 5 cm in the high altitude. The estimated total carbon stock in low, middle and high altitude were 162.0299±9.0944 t ha-1 and 142.7676±0.3984 t ha-1 and 132.923±18.8068 tons ha- 1, respectively, which showed a significant difference (P< 0.05). Similarly, soil organic carbon had a significance different across depths(0-30cm,30-60cm) in altitudinal gradients (P< 0.05). The largest carbon pool in all the three altitudinal gradients were soil organic carbon pool sinking the highest carbon amount of 162.02±90,142.76±0.39,132.92±18 C tons ha- 1 for low, middle and high altitude respectively. The results showed that Muhabura Volcano can be important for carbon stocks. Therefore, effective conservation of this mountain has a considerable contribution to climate change mitigation and biodiversity conservation. Thus, there is need to continue enforced protection against anthropogenic disturbances including fires and invasive exotic species at Muhabura Volcano, that could interfere with further carbon sinking, storage and biodiversity conservation.