Impacts of Prosopis juliflora L. on Soil Seed Bank Flora in Amibara Rangeland of Afar Regional State, Ethiopia

Abstract

Background: Prosopis juliflora L. is an evergreen exotic weedy species seriously devastating valuable rangeland resources in arid and semi-arid parts of Ethiopia. Its increasing alarming rate of invasiveness had affecting the livelihood of the pastoral communities in Amibara rangeland of Afar National Regional State. Therefore, the aim of this study was to investigate the effects of Prosopis juliflora L. on soil seed bank flora. Methods: The total of 20 soil samples were collected from five sites by measuring sample quadrats of (20 m × 20 m) area were laid out and the soil samples from each quadrant were taken from 5 sub-quadrats/m2, one from the center and four from the corners, at two depths (0-3 cm and 3-10 cm). The soil samples from the identical layers were mixed in plastic bags to form composite sample. Finally, the composite samples were transported to the Haramaya University to conduct seed germination test in the greenhouse. The soil samples were spread thinly (2 cm thickness) over sterilized soil in shallow trays (20 cm × 25 cm) placed on a bench and allowed for seed germination. Result: The total of 38 herbaceous plant species /m2 belongs to 16 families were emerged in the upper and lower layer (0-3 cm and 3-10 cm) of the soil seed bank samples. The highest values of species diversity were (3.17) in Awash-arba, (3.15) in Alaydagi, (3.04) in Kurkura within m2 area at the depth of 0-3 cm. While the least diversity values of 2.75 in Melka-Werer and 2.77 was recorded in Sarkamo. Jaccard’s coefficient similarity index was exhibited high species similarity of 55.6% in the upper soil seed bank layers (0-3 cm) in Melka-were and Sarkamo. Whereas, species similarities of 45.2% were obtained in the lower layer (3-10 cm) soil seed banks in Awash-arba and upper layer soil seed bank in Alaydagi respectively. While species similarity was decreases as 31.8% in the lower layer soil seed banks in Sarkamo and Kurkura. Increasing species richness and the diversity was also noticed in under open canopy upper layer soil seed bank samples, while decreasing richness and diversity observed in under closed canopy. This indicates that the Prosopis juliflora L. tree has high growth retarding potential on its under canopy soil seed bank flora and in the lower layer soil seed bank samples also.