www.elsevier.com/locate/jnlabr/yjare Journal of Arid Environments Journal of Arid Environments 58 (2004) 134–153 Some biological characteristics that foster the invasion of Prosopis juliflora (Sw.) DC. at Middle Awash Rift Valley Area, north-eastern Ethiopia Hailu Shiferaw a , Demel Teketay b, *, Sileshi Nemomissa c , Fassil Assefa c a P. O. Box 2811, Addis Abeba, Ethiopia b Ethiopian Agricultural Research Organization, P.O. Box 2003, Addis Abeba, Ethiopia c Department of Biology, Addis Abeba University, P. O. Box 1176, Addis Abeba, Ethiopia Received 23 December 2002; accepted 20 August 2003 Abstract A study on some biological features of Prosopis juliflora, a multipurpose leguminous species introduced to Ethiopia, was carried out at Melka-Worer, North-east Ethiopia. The study focused on the number of seeds produced in a pod during the study period, seed dispersal through droppings of animals, soil seed banks, seed germination and stumping height of trees and coppicing ability of P. juliflora. The overall mean number of seeds was 2374seeds/pod. The width and length of seeds ranged between 0.8–1.7 and 8–29 cm, respectively. The mean weight of a seed of Prosopis was 0.0275g70.001 (S.E.) while there were 36,000–37,000seeds/ kg. The number of seeds recovered from 1 kg of droppings of each animal ranged between 760 (goats) and 2833 (cattle), suggesting that cattle are the major dispersers of seeds of the study species followed by warthogs, camels and goats. There was a highly significant difference in vertical distribution of the seed density of P. juliflora recovered from the soil samples while the horizontal distribution exhibited a great disparity in the density of soil seeds among the sample plots. The total mean soil seed density, in the litter layer and down to 9 cm depth, was 1932seeds/m 2 (7307S.E.). Germination of seeds of P. juliflora differed significantly among the various treatments. The highest germination percentage was obtained from seeds that were treated with mechanical scarification (100%) and sulfuric acid for 15–60min (97–99%). About 37% and 47% of the seeds recovered from droppings of goats and warthogs, respectively, germinated. All stumped trees of P. juliflora produced coppices except those stumped at 10 cm below ground. The overall mean number of coppices at the studied plots was 17.870.9 (S.E.) while the overall mean height of coppices, in 6 months after stumping, was 68.4 cm72.7 (S.E.). The results clearly demonstrated that Prosopis is equipped with a number of biological ARTICLE IN PRESS *Corresponding author. Tel.: +251-1-454-452; fax: +251-1-461-251. 0140-1963/$-see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaridenv.2003.08.011