Estimation of seasonal water use of Faidherbia albida (Delile) A.Chev. in a Sahelian agroforestry parkland

Description of the subject. Faidherbia albida is recognized as a promising agroforestry species. In agroforestry systems, tree water use (TWU) dynamics is a key component of its impacts on associated crop yield and the water balance. Little is known about F. albida water uptake while an estimation of the ecosystem water balance is crucial in the context of climate change. Objectives. The aim of this study is to assess F. albida water use along a year and the implication of tree size, season and phenology. Method. Five mature trees were selected in an agroforestry parkland in the groundnut basin near Niakhar village in Senegal to monitor sap flow. Tree water use (TWU) or (Q) was calculated and climate conditions, soil water content and leaf phenological phases were also continuously recorded. Results. Results revealed a significant TWU variability between rainy and dry seasons and between leaf phenological stages. The maximal water use values were observed in the first part of the dry season between December and January, when the trees are in full leaf, with large between-tree variability, from 118 to 261 l·tree-1·d-1. The TWU slowly decreased during the dry season and reached minimal values during the leafless phase which takes place during the rainy season. Conclusions. The average annual water use was estimated at about 40,000 l·tree-1·year-1, i.e. 27 mm·tree-1·year-1, which represents 5.3% of 2019 annual rainfall (513 mm). The significant relationship of TWU with leaf phenological phases (R2 = 0.81) supports the possibility that a simple model can estimate the tree water use.