title: Is the WBE model appropriate for semi-arid shrubs subjected to clear cutting?
abstract: It is crucial to understand the adaptive mechanisms of woody plants facing periodic drought to assess their vulnerability to the increasing climate variability predicted in the Sahel. Guiera senegalensis J.F.Gmel is a semi-evergreen Combretaceae commonly found in Sahelian rangelands, fallows and crop fields because of its value as an agroforestry species. We compared canopy leafing, and allometric measurements of leaf area, stem area and stem length and their relationships with leaf water potential, stomatal conductance (gs) and soil-to-leaf hydraulic conductance (KS-L), in mature and current-year resprouts of G. senegalensis in Sahelian Niger. In mature shrubs, seasonal drought reduced the ratio of leaf area to cross-sectional stem area (AL : AS), mainly due to leaf shedding. The canopy of the current-year resprouts remained permanently leafed as the shrubs produced leaves and stems continuously, and their AL : AS ratio increased throughout the dry season. Their KS-L increased, whereas gs decreased. West, Brown and Enquist's (WBE) model can thus describe allometric trends in the seasonal life cycle of undisturbed mature shrubs, but not that of resprouts. Annual clear cutting drives allometric scaling relationships away from theoretical WBE predictions in the current-year resprouts, with scaling exponents 2.5 times greater than those of mature shrubs. High KS-L (twice that of mature shrubs) supports this intensive regeneration process. The adaptive strategy described here is probably common to many woody species that have to cope with both severe seasonal drought and regular disturbance over the long term.
authors.affiliation: Faculté d'Agronomie et des Sciences de l'Environnement, Université de Maradi, BP 465 Maradi, Niger IRD-UMR HydroSciences Montpellier, Université Montpellier 2, 34095 Montpellier Cedex 5, France hassanebil-assanou.issoufou@ird.fr.
authors.forename: Hassane Bil-Assanou
authors.initials: HB
authors.lastname: Issoufou
authors.affiliation: CEFE-CNRS-UMR DREAM, Université de Montpellier 2, 34293 Montpellier Cedex 5, France Departamento de Biologia, Universidade Federal de Lavras, CP 3037, CEP 37200-000, Lavras, MG, Brazil.
authors.forename: Serge
authors.initials: S
authors.lastname: Rambal
authors.affiliation: UPS-UMR CESBIO, 18 Avenue Edouard Belin, 31401 Toulouse Cedex 4, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Le Dantec
authors.affiliation: IRD-UMR HydroSciences Montpellier, Université Montpellier 2, 34095 Montpellier Cedex 5, France.
authors.forename: Monique
authors.initials: M
authors.lastname: Oï
authors.affiliation: CNRS-UMR Laboratoire d'étude des Transferts en Hydrologie et Environnement, Bâtiment OSUG-B, Domaine universitaire, BP 53, 38041 Grenoble cedex 09, France.
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Laurent
authors.affiliation: Faculté d'Agronomie et des Sciences de l'Environnement, Université de Maradi, BP 465 Maradi, Niger.
authors.forename: Mahamane
authors.initials: M
authors.lastname: Saadou
authors.affiliation: IRD-UMR HydroSciences Montpellier, Université Montpellier 2, 34095 Montpellier Cedex 5, France.
authors.forename: Josiane
authors.initials: J
authors.lastname: Seghieri
mesh_terms: D000222:Adaptation, Physiological; D002980:Climate; D029764:Combretaceae / Q000254:growth & development*; D055864:Droughts; D017753:Ecosystem; D004777:Environment; D008954:Models, Biological; D018515:Plant Leaves / Q000254:growth & development*; D018547:Plant Stems / Q000254:growth & development; D013312:Stress, Physiological; D014867:Water; D014934:Wood
chemical_list: D014867:Water
keywords: Guiera senegalensis; adaptive mechanism; allometry; resource allocation; resprouts; water-limited environment