Growth and biomass production of some selected native and introduced tree/shrub species under severely degraded landscapes of west showa zone of oromiya regional state, central highlands of Ethiopia

Abstract

Rehabilitation of degraded lands through tree/shrub planting could improve land productivity, rural livelihoods, biodiversity and other ecological services. The growth and early performance of six exotic, five indigenous, and a mixture of both origins were evaluated on a severely degraded land of Fotololo, West Shoa, Ethiopia. A total of sixteen treatments were arranged in randomized complete block design with three replications. Each plot contained 25 trees/shrub species planted at the spacing of 1.5m x 1.5m. The survival percentage of indigenous species after 42 months was generally lower than the exotic ones. The lowest survival percentage among indigenous species was recorded by Albizia gummifera (J.F.Gmel.) C.A.Sm. (4%) while the highest was recorded by Olea europaea subsp. cuspidata (Wall. & G.Don) Cif. (51%). Among the exotic species, Sesbania sesban (L.) Merr. and Acacia saligna (Labill.) Wendl. had the highest survival percentage (80 and 71%, respectively) but Acacia decurrens Willd. had the lowest rate (20%). The maximum height 3.75m and root collar diameter 49.9mm were attained by S. sesban (L.) Merr. followed by Acacia saligna (Labill.) Wendl. and Eucalyptus camaldulensis Dehnh. However, all indigenous species had grown poorly, with the height growth range of 0.52±0.39m (Albizia gummifera (J.F.Gmel.) C.A.Sm.) to 1.20±0.26m (Millettia ferruginea (Hochst.)). The growth and survival of C. africana Lam., Juniperus procera Hochst. ex Endl., Millettia ferruginea (Hochst.) and Olea europaea subsp. cuspidata (Wall. & G.Don) Cif. were slightly improved when they were planted in mixture with either of the following exotic species. The dry biomass of the undergrowth species varied between 448 gm-2 (from Olea europaea subsp. cuspidata (Wall. & G.Don) Cif. plot) and 952 gm-2 (from Sesbania sesban (L.) Merr. plot. Rhodes was the dominant species in the experimental site and followed by Digitaria, Cyanadon and Trifolium species. In conclusion Sesbania sesban (L.) Merr. and Acacia saligna (Labill.) Wendl. are the outstanding species with best growths and survival rate and they can be used as entry species to rehabilitate degraded lands at Fotololo and other areas with similar agro ecological conditions.