Original article Hydraulic redistribution study in two native tree species of agroforestry parklands of West African dry savanna Jules Bayala a, *, Lee Kheng Heng b , Meine van Noordwijk c , Sibiri Jean Ouedraogo a a De ´partement Productions Forestie `res, Institut de l’Environnement et de Recherches Agricoles, 03 BP 7047 Ouagadougou 03, Burkina Faso b Soil and Water Management and Crop Nutrition Section, IAEA, Wagramer Strasse 5, P.O. Box 100, A-1400 Vienna, Austria c World Agroforestry Center, ICRAF S.E. Asia, JI. CIFOR, Situ Gede, Sindang P.O. Box 161, Bogor, Indonesia article info Article history: Received 18 September 2007 Accepted 30 June 2008 Published online 15 August 2008 Keywords: Hydraulic redistribution Modelling Parkland systems Tree–soil–crop interactions abstract Hydraulic redistribution (HR) in karite ´(Vitellaria paradoxa) and ne ´re ´(Parkia biglobosa) tree species was studied by monitoring the soil water potential (j s ) using thermocouple psychrometers at four compass directions, various distances from trees and at different soil depths (max depth 80 cm) during the dry seasons of 2004 and 2005. A modified WaNuL- CAS model was then used to infer the amount of water redistribued based on j s values. Tree transpiration rate was also estimated from sap velocity using thermal dissipative probes (TDP) and sapwood area, and the contribution of hydraulically redistributed water in tree transpiration was determined. The results revealed on average that 46% of the psychrometer readings under karite ´ and 33% under ne ´re ´ showed the occurrence of HR for the two years. Soil under ne ´re ´ displayed significantly lower fluctuations of j s (0.16 MPa) compared to soil under karite ´ (0.21 MPa). The results of this study indicated that the existence of HR leads to a higher j s in the plant rhizosphere and hence is impor- tant for soil water dynamics and plant nutrition by making more accessible the soluble elements. The simulation showed that the amount of water redistributed would be approx- imately 73.0 L and 247.1 L per tree per day in 2005 for karite ´ and ne ´re ´ , and would represent respectively 60% and 53% of the amount transpired a day. Even though the model has certainly overestimated the volume of water hydraulically redistributed by the two species, this water may play a key role in maintaining fine root viability and ensuring the well adaptation of these species to the dry areas. Therefore, knowledge of the extent of such transfers and of the seasonal patterns is required and is of paramount importance in park- land systems both for trees and associated crops. ª 2008 Elsevier Masson SAS. All rights reserved. 1. Introduction In the parklands of the Sahel, farmers practise agroforestry by retaining trees that provide edible fruits and growing cereal crops between and under them, despite the regular occur- rence of water shortage during the growing season. Trees preserved in the parkland systems of Burkina Faso in West Africa are dominated by Vitellaria paradoxa C.F. Gaertn or * Corresponding author. Tel.: þ226 50 33 40 98; fax: þ226 50 31 50 03. E-mail address: jules.bayala@coraf.org (J. Bayala). available at www.sciencedirect.com journal homepage: www.elsevier.com/locate/actoec 1146-609X/$ – see front matter ª 2008 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.actao.2008.06.010 acta oecologica 34 (2008) 370–378