Distribution of invasive plant species Prosopis juliflora (mesquite) in relationship to biophysical factors in Rombo, Mwanga, and Same districts

Report 2016

Prosopis juliflora is among aggressive invaders in tropical, arid and semi-arid natural grasslands. This plant which belongs to the Fabaceae family is native to Mexico, South America and the Caribbean, has become established as an invasive weed in many places including Africa (http://www.cabi.org/isc/datasheet/43942). In many areas where it is not native, the plant was firstly intentionally introduced and planted for soil and water conservation purposes, ornamental, as well as for fuelwood and fodder (Choge et al., 2002; de Souza Nascimentoa, 2014). Its competitive advantage over other vegetation is based on its ability to fix nitrogen and its tolerance against drought and soil saline condition (Felker et al., 1981; Khan et al., 1986; Singh 1996). Its thorniness and bushy habit enable it to quickly block paths and make whole areas impenetrable for human and livestock. P. juliflora tree is 3-12 m tall, with spreading woody cylindrical branches. It is more or less round- or flat-topped with persistent green foliage and somewhat spiny (Burkart, 1976).The plant grows in a wide range of soils - from sandy to clayey soils. It is generally found in areas where water and soil fertility are the principal agents limiting plant growth. Prosopis species are generally cross-pollinated (Simpson, 1977), although some limited self- pollination (4%) has been observed in P. juliflora (Sareen and Yadav, 1987). The tree produces a very large numbers of flowers, but few are fertile with high rates of ovary abortion (Goel and Behl, 1995). Negative impacts of the tree include loss in agricultural and pasture productivity, biodiversity loss due to its suppression power, and deaths of livestock due to eating of the pods produced by the tree (Choge et al., 2002). Its pollen has been identified among the respiratory allergens in tropical countries (Killian and McMichael, 2004; Dhyani et al., 2006). Positive benefits include production of fuelwood, charcoal, timber and sale of the pods to the feed processing industry (Maundu et al., 2009). The tree is also widely planted for soil conservation, hedgerows, and as an ornamental tree (Pasiecznik et al., 2001).This study intended to identify areas already infested with the tree in Rombo, Mwanga, and Same districts; and to relate their spatial distribution with biophysical factors such as soils, lithology, landforms, and agroecological zones.