Survey and documentation of the potential and actual invasive alien plant species and other biological threats to biodiversity in Awash

The study was conducted at the Awash National Park (ANP) Ethiopia, to document Invasive Alien Species (IAS) and to assess the spread of Prosopis juliflora (Sw.) DC. A total of 64 sample plots were laid systematically along the altitudinal gradient of 750 to 1916 m. Potential IAS were recorded. IAS which may threaten biodiversity of the park includes species such as Prosopis juliflora, Parthenium hysterophorus L., Cryptostegia grandiflora Roxb. ex R. Br. , Parkinsonia aculeata L., Senna occidentalis (L.) Link, Datura ferox L. and Xanthium strumarium L. Except P. juliflora and P. hysterophorus, all others were not recorded in Ethiopia as IAS. P. juliflora was recorded in three plots with cover of 1% to 10%. P. juliflora was also found spread in different parts of the park particularly following the route of cattle movement. P. hysterophorus was recorded in and around nine sample plots. Plot 46, 47 and 48 were highly infested by P. hysterophorus which covered more than 60, 70 and 80% of the ground layer respectively. C. grandiflora was recorded in 11 plots with cover ranging from 1% to 35%. In view of all the natural as well as anthropogenic threats to the biodiversity of the Park, the ANP is at high risk. The rich biodiversity needs immediate management intervention.


Description of the study area
The study was conducted in

Data Collection
The following environmental parameters were measured for each sampling plot: -Altitude, by using pocket altimeter and Garmin GPS; -Slope, by using clinometer and -Geographical coordinates, by using Garmin GPS.
The average cover abundance of plant species from 64 sampling plots recorded by visual estimation of the percentage foliage cover of each species in the sample plot and recorded as percentage.

Results and Discussion
Average cover abundance of The main rainy season is from July to September, with a short rainy season from February to April.
The nature of rainfall in the study area is irregularly distributed and the mean annual rainfall is 550.9 mm (Ebro et al. 2004).Sweden, in 1985.He is one of the leading experts in the flora of Ethiopia and Eritrea and he is also the author /co-author of many scientific articles in refereed journals and also a number of books in the field.

Sampling Design and data collection
Ethiopia spans a remarkable number of the world's broad ecological regions due to its dramatic geological history, broad latitudinal spread and immense altitudinal range.This range from the depressions in the Afar (126 m below sea level) to the spectacular mountaintops of Ras Dashen in the north (4620 m) and the Bale Mountains in southeast Ethiopia (4272 m).This variety of habitats also supports a rich variety of different species which contributes to the overall biodiversity of the country (IBC 2005).Biodiversity conservation is the protection, restoration and sustainable management of wildlife and natural resources such as forests and water and the biological Abstract The study was conducted at the Awash National Park (ANP) Ethiopia, to document Invasive Alien Species (IAS) and to assess the spread of Prosopis juliflora (Sw.)DC.A total of 64 sample plots were laid systematically along the altitudinal gradient of 750 to 1916 m.Potential IAS were recorded.IAS which may threaten biodiversity of the park includes species such as Prosopis juliflora, Parthenium hysterophorus L., Cryptostegia grandiflora Roxb.ex R. Br. , Parkinsonia aculeata L., Senna occidentalis (L.) Link, Datura ferox L. and Xanthium strumarium L. Except P. juliflora and P. hysterophorus, all others were not recorded in Ethiopia as IAS.P. juliflora was recorded in three plots with cover of 1% to 10%.P. juliflora was also found spread in different parts of the park particularly following the route of cattle movement.P. hysterophorus was recorded in and around nine sample plots.Plot 46, 47 and 48 were highly infested by P. hysterophorus which covered more than 60, 70 and 80% of the ground layer respectively.C. grandiflora was recorded in 11 plots with cover ranging from 1% to 35%.In view of all the natural as well as anthropogenic threats to the biodiversity of the Park, the ANP is at high risk.The rich biodiversity needs immediate management intervention.

Fig 1 .
Fig 1. Beisa Oryx, one of the many species with high conservation value of the Awash National Park.
proximity of ANP to Amibara (one of the Districts bordering it, where there is a high infestation of P. juliflora.Together with uncontrolled movement of both wild and domestic animals to the Park, the invasion of the Park by P. juliflora plant Species and the spread of P. juliflora in the Park and to identify other threats to the Biodiversity of the Park in order to provide information for appropriate decision making on the biodiversity conservation of ANP. current status of plant diversity of ANP as well as the spread of invasive plant species is not available.Due to the close abundance of Parthenium hysterophorus L., Cryptostegia grandiflora Roxb.ex R. Br. and Prosopis juliflora (Sw.)DC.Even though, not all alien species will become invasive or threaten the environment, this is an area in which an early investigation should be made to reduce the potentially wide-ranging impacts when they do become invasive, and because of the difficulties, including financial costs and in reversing the impacts.Invasive Alien Species are species which are an introduced species which invades natural habitats, non-native (or alien) to the ecosystem and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.The study showed that, in the ANP there are plant species which are known to be invaders, noxious weeds and escape from cultivation that became semi naturalized.Plant species which were observed in different parts of the Park and which are alien to the ecosystem in general and to the ANP in particular; with actual and future invasive potential and which needs serious management measures are Prosopis juliflora (Sw.)DC., Parthenium hysterophorus L., Cryptostegia grandiflora Roxb.ex R. Br., Parkinsonia aculeata L., Senna occidentalis (L.) Link, Datura ferox L., Xanthium strumarium L. Except encountered in each sample plot were recorded and their cover was recorded by visual estimation of the percentage foliage cover of each species in the sampling plot and recorded as percentage.Sampling sites in ANP. Park areas where distributed among grasslands such as the Illala Sala area.Other inaccessible areas and areas with security problems were excluded from sampling.
three most abundant alien plant species is shown in Fig. 2. Appendix 1 shows the relative coverage of the species recorded in the relevés.The results showed the greater River, and covers 756 km 2 .The vegetation of the study area is described as open grassland, bushland/shrubland and riverine vegetations (Jacobs & Schloeder 1993), woodland and grassland with altitudinal range between 750 and 1916 m.a.s.l.(Gamachu 1977).
During the reconnaissance survey, based on visual observation and by consideration of the vegetation and other environmental gradients, the ANP was grouped into seven vegetation stands.Data collection was conducted during October to November 2008 and March 2009.The assessment was conducted along altitudinal gradient ranging from 750 to 1916 m by using systematic sampling design.Nine transect lines were established systematically at different places based on identified vegetation stands.In nine transects, 64 sample plots each with a size of 20 x 20 m were established at every 200 m interval along the transect or 50m altitudinal drops when there is a steep slope.All woody vascular plant species as well as IAS ISSN 1989-8649 Manag.Biolog.Invasions, 2011, 2 Prosopis juliflora and Parthenium hysterophorus which were recorded in Ethiopia as IAS, the other five species were not so far recorded as IAS in Ethiopia.Even Parkinsonia aculeate is grown by many government and non-government nursery sites and being distributed to growers in different parts of the country.Among the different altitudinal ranges covered, all the IAS were observed in the intermediate to low altitude between 770 to 1047 m a.s.l. which are plain areas, river sides, foot of mountains and road sides.The higher altitude (1094 to 1916 m a.s.l.) from the middle of Mount Fentale to the top up to the edge of the volcanic crater, which is mainly dominated by the endemic tree species Acacia prasinata Schweinf.is so far free from such IAS.This may be because of its inaccessibility.Prosopis juliflora is one of the IAS which becomes a threat globally as well as locally in Ethiopian.In Ethiopia P. juliflora has become a problematic species expanding at an alarming rate in Afar and Somali regions.P. juliflora is extensively spreading following the main road of Djibouti -Addis Ababa, passing several towns like Mille, Gewaine and others.It has reached to Awash and Metehara towns where the ANP 6 is located in between.Among the 64 sample plots of the study, P. juliflora was recorded in plots 30, 31 and 32 with cover percentage of 10, 3 and 1% respectively (Fig. 2).It is extensively emerging in places where cattle overnight for long period of time.Also out of the sample plots there are several parts of the Park were P. juliflora is growing (Fig. 3).The direction of the introduction of P. juliflora into the Park also coincided with the major direction of pastoralist movement to the Park, which is from the northeast and south part of the Park by Afar and Kereyu/Ituu pastoralists respectively.Even though, there is no written document when and at which place of the Park was P. juliflora first observed, the age of the trees shows that it is a recent introduction which could be during the last three to five years.As it is shown in the map the direction of the spread of P. juliflora coincide with the pastoralist's movement given by Jacobs & Schloeder (1993), except a single tree observed around Kereyu lodge which is found in area where there is no cattle movement.The two major possible introduction and direction of spread of P. juliflora are expected to be from northeast and south part of the Park by Afar and Kereyu/Ituu pastoralists respectively.

Fig. 6 .Fig. 8 .Fig. 9 .
Fig. 6.P. aculeata, Planted as ornamental around Kereyu lodge of ANP has grown in some parts of the Park as semi naturalized plant.
Associate Research Officer working in Institute of Biodiversity Conservation, Ethiopia.He is a Botanist with MSc degree in Botanical Sciences from Addis Ababa University and B.Sc degree in Plant Sciences from Alemaya University, Ethiopia.He is now a PhD.Candidate in Environmental Science in Addis Ababa University, Ethiopia and working on Biodiversity Conservation, Invasive Alien Species, Ecology and Climate change related issues.Curator of Gene Bank, Institute of Biodiversity Conservation, Addis Ababa, Ethiopia), was born in Bale/Ethiopia in 1967.He obtained his BSc.degree from the Asmara University in 1989 (Eritrea), MSc.degree from the University of Addis Ababa (Ethiopia) in 1997 and PhD degree from the University of Oslo (Norway) in 2007.He is one of the experts in the flora of the region and also the author of some scientific articles in the field.Leader of the Ethiopian Flora Project & Keeper of the National Herbarium, Plant Biology and Biodiveristy Management Unit, Faculty of Life Sciences, College of Natural Sciences, Addis Ababa University, Addis Ababa), was born in Shewa in 1953.He obtained his BSc.and MSc.degrees from the University of Addis Ababa in 1978 and 1980 respectively, and his PhD degree from the University of Uppsala,