Status of soil properties of scattered Faidherbia albida (Del) in agricultural landscapes in Central Highland of Ethiopia

Scattered trees in general and scattered Faidherbia albida in particular are preserved in agricultural landscapes in Ethiopia. A study on this tree species was conducted at Meskan District of Gurage Zone, Ethiopia with the objectives of assessing the status of soil properties under it and its population distribution in agricultural landscapes. Twenty four  soil samples from the surface layer (0-10 cm) were taken from under six  isolated mature F. albida trees at 3 concentric transects (1, 3 and 5 m) from the tree trunk  and compared with soils taken from the adjacent open areas, 12 m far from the trees. In addition, 24 undisturbed soil samples were also collected from same points using core samplers for bulk density and moisture content determinations. The collected soil samples were analyzed following standard laboratory procedures. Assessment of the population distribution of the species was carried out at three different altitudinal zones, that is,1800-2000 m above sea level (asl), 2000-2200 m asl and 2200-2400 m asl and from four land use types (homestead, farmlands, woodlots and grazing land). A complete count and Y frame transect sampling methods were used to estimate number of stem per ha. The results revealed that organic matter (OM%), organic carbon (OC%) and total nitrogen (TN%) significantly differ between radial distances. The three parameters, were higher at 1 m distance compared with the values at 5 and 12 m distances. Though the difference is statistically not significant, available P and moisture content (MC) showed a decreasing trend, and bulk density (BD) and carbon nitrogen ratio (C/N) showed an increasing trend with increasing distance from the trees trunk. Population status of F. albida in the farms is dominated by higher diameter classes, with only 2% share of stems in the younger DBH-class of less than 5 cm. This may not indicate a threat to the species as it appear  as the community do not cut and harvest the whole tree but only lop which eventually may prolong the life span of the trees. Thus, this finding suggests that scattered F. albida trees are important agro-forestry resource to sustain soil fertility and subsequently crop yields. They are also important sources of multiple products such as fodder and shade for livestock during dry period, fuel and fencing material for households.   Key words: Faidherbia albida, soil property, population status, sustainability, Ethiopia.