The importance of early successional shrubs for recruitment of african wild olive (Olea europaea ssp. cuspidata) in Central Tigray, Ethiopia

Abstract

Recruitment of a late successional tree species, African wild olive (Olea europaea subsp. cuspidata; Oleaceae), was examined in protected and grazed areas in the Geba river catchment of central Tigray, northern Ethiopia, using T-square plotless sampling. The following hypothesis was tested: recruitment of O. europaea is higher under certain early colonizing shrubs compared to within gaps and under other shrubs. Both in grazing land and protected areas, recruits were exclusively found under shrubs, predominantly under Euclea schimperi, although Acacia etbaica was dominant by far in all sampled land uses. Structural traits of shrubs explain this disparity. However, early results of further research suggest that E. schimperi shrubs probably act as preferential perching sites for frugivorous birds and that dispersal of Olea propagules is directed to dense E. schimperi shrubs with a high number of stems at ground level. The application of appropriate protection of early successional shrubs combined with simple silvicultural measures can therefore significantly enhance natural regeneration of indigenous woodlands in the region without having to rely on expensive plantation activities.