Paper short abstract:

The lowlands of Baringo are semi-arid and the vegetation is dominated by A. tortilis and P. juliflora. We aim at understanding the distribution patterns of those species and its relationship to drought tolerance. We present first results on water use efficiency and relate them to soil measurements.

Paper long abstract:

Full list of authors: D. Otieno, N. Nyamari, D. Ondede, T. Kramm, P. Olewe, A. Kolb, G. Bareth, L. Biber-Freudenberger, C. Bogner

The lowlands of Baringo County (900 to 1200 m asl) are semi-arid with a bi-modal rainfall averaging 635 mm annually against a mean annual evaporation rate of 1,100 mm. The average minimum and maximum air temperatures are 20 and 30 °C. The vegetation is dominated by the genus Acacia, mostly overrepresented by the species A. tortilis, endemic to the lowlands and Prosopis juliflora, a neophyte that was introduced in the area in the 1970s. While A. tortilis is sedentary and remains relatively resistant to drought stress in their increasingly dry environment, P. juliflora is more versatile and prolific and has spread into most parts of the lowlands. Factors that promote this distribution pattern of the two species, however, remain unclear, but are likely to be related to their ability to withstand drought stress. In this study, we examine the mechanisms of stress resistance employed by A. tortilis and P. juliflora within their natural distribution range in Marigat, Baringo County. We present results of different data collection methods deployed to investigate water sources, root uptake, transport, and use by trees. These results are linked to our first soil measurements conducted in a fish-bone design along transects of rural roads in Marigat to understand how hydrological changes resulting from road influence the distribution patterns of A. tortilis and P. juliflora in Baringo County.