Diversity, regeneration status, and population structures of gum and resin producing woody species in Borana, Southern Ethiopia

Abstract

Severe drought and large-scale ecosystem degradation are the two major threats exacerbating livelihood vulnerability of the pastoral and agropastoral communities in Borana Zone, southern Ethiopia. Strategic integration and sustainable management of the vast gum and resin bearing dry forests offer significant socioeconomic and ecological opportunities to enhance adaptation of these communities to adverse climatic variability, while enhancing ecosystem resilience. This study was carried out to investigate the diversity, abundance, distribution, and population structure of gum and resin bearing species in Borana drylands. Surveys were carried out in two districts: Arero and Yabello. Seventy-five (20 × 20 m) quadrats were established at 500 m intervals along transects in seven localities. Forty-six woody species distributed in 16 families and 25 genera were encountered. Gum and resin producing species comprised about 42 and 61% of the total number of species, 49 and 68% of the density ha-1, and 73 and 84% of the total basal area at Arero and Yabello, respectively. Regeneration and diameter class distribution showed clear signs of healthy populations, except for a small number of species, which exhibited bell-shaped diameter class distribution patterns. The results revealed that Borana Zone hosts more diverse commercial gum and resin bearing species compared to the northern part of the country, where organized production and marketing of gum and resin are well developed, and other relatively similar places, such as Middle Rift Valley and the neighbouring Somali region in Ethiopia. Such diversity, abundance, and the overall positive regeneration status of most of the gum and resin bearing species in Borana make up a solid and healthy basis for promoting the sustainable management of woodland resources through organized production and commercialization of high value oleo-gum resins.