Impact of Land Use Type on Soil Seed Bank Flora in Chilimo Forest, Ethiopia: Implications for Natural Restoration of Vegetation

Abstract

A very long history of human interference and pressure from population growth has imparted different land use types in the Chilimo forest: shrub land, closed forest, Cupressus lusitanica plantation, Eucalyptus plantation, Juniperus procera dominated stand, Olea europaea subsp. cuspidata dominated stand, open forest, Podocarpus falcatus dominated stand, abandoned arable land, and grassland. A total of 100 plots (each 20 m x 20 m) were used in ten habitat types (10 plots in each) for the collection of data on the soil seed bank and standing vegetation. Soil samples were collected from within small quadrats (15 cm x 15 cm) from four successive soil layers. A total of 105 plant species were identified from the soil seed bank with total densities ranging between 4991 and 11017 seeds/m2. Of the total recorded species in the soil seed bank, herbaceous species were represented with the largest number (87.6%) whereas the contribution of woody species was low (11.4%). The highest number of species was recorded from the closed canopy stand while the highest density of seeds was found in the arable land. The overall vertical distribution of seeds showed the highest densities occurring in the upper 3 cm soil depth and gradually decreasing with increasing depth, except in the arable land. There was a significant difference among the habitat types in the density of soil seed bank suggesting different types, level and frequency of disturbance on different habitat types. The very low similarity between the soil seed bank and aboveground flora is reflective of both the current and past standing vegetation.