INVESTIGATIONS ON CANOPY FEATURES OF THREE INDIGENOUS WOODLAND TREE SPECIES OF ETHIOPIA

Abstract

Canopy features, diversity of undercanopy vegetation, and undercanopy soil chemical characteristics of three indigenous woodland tree species namely: Acacia tortilis (Forssk.) Hayne, Acacia senegal (L.) Willd, Balanites aegyptiaca (L.) Del. were studied, The objective of the study was to explore the potential of the tree species for use in agroforestry systems. The study was conducted at three different sites within the Great Rift Valley at Adamitulu area, Abijata Shalla and Awash National Parks. At each site a total of 15 study trees were selected from 50 x 50 m releves. From each tree, data on tree height, diameter at breast height (DBH), canopy depth and canopy diameter were collected. Effect of treeson undercanopy vegetation diversity was assessed by estimating cover of undercanopy herbaceous vegetation. Soil samples were
collected beneath and outside tree canopies to investigate the influence of tree species on undercanopy soil. A. tortilis had the highest DBH (0.42 ± 0.12) and canopy diameter (13.64 ± 2.25) whereas the highest tree height (5.18 ± 0.77) and canopy depth (2.94 ± 0.73) were recorded for B. aegyptiaca. The highest undercanopy vegetation diversity was recorded for A. tortilis (2.13) followed by A. senegal (1.92) and B. aegyptiaca (1.78). In general, surface soil organic carbon, total nitrogen, available phosphorus, exchangeable potassium, and electrical conductivity were higher under tree canopies for all the study trees compared to outside canopy soils. Soil conductivity, organic carbon, total nitrogen and available phosphorus were found to be highest for surface soils,
under A. tortilis. However, no difference in soil nutrient content among the tree species were found at greater soil depth. Implications of the findings for agroforestry systems are discussed.