Arbuscular mycorrhizal associations in Boswellia papyrifera (frankincense-tree) dominated dry deciduous woodlands of Northern Ethiopia

This study assessed the arbuscular mycorrhizal (AM) status of Boswellia papyrifera (frankincense-tree) dominated dry deciduous woodlands in relation to season, management and soil depth in Ethiopia. We studied 43 woody species in 52 plots in three areas. All woody species were colonized by AM fungi, with average root colonization being relatively low (16.6% – ranging from 0% to 95%). Mean spore abundance ranged from 8 to 69 spores 100 g⁻¹ of dry soil. Glomus was the dominant genus in all study sites. Season had a strong effect on root colonization and spore abundance. While spore abundance was higher (P < 0.001) in the dry season in all three study sites, root colonization showed a more variable response. Root colonization was reduced in the dry season in the site that was least subject to stress, but increased in the dry season in the harshest sites. Management in the form of exclosures (that exclude grazing) had a positive effect on spore abundance in one of the two sites considered. Spore abundance did not significantly differ (P = 0.17) between the two soil depths. Our results show that in this arid region all trees are mycorrhizal. This has profound consequences for rehabilitation efforts of such dry deciduous woodlands: underground processes are vital for understanding species adaptation to pulsed resource availability and deserve increasing attention.