title: Deciduous and evergreen trees differ in juvenile biomass allometries because of differences in allocation to root storage.
abstract: OBJECTIVE
  Biomass partitioning for resource conservation might affect plant allometry, accounting for a substantial amount of unexplained variation in existing plant allometry models. One means of resource conservation is through direct allocation to storage in particular organs. In this study, storage allocation and biomass allometry of deciduous and evergreen tree species from seasonal environments were considered. It was expected that deciduous species would have greater allocation to storage in roots to support leaf regrowth in subsequent growing seasons, and consequently have lower scaling exponents for leaf to root and stem to root partitioning, than evergreen species. It was further expected that changes to root carbohydrate storage and biomass allometry under different soil nutrient supply conditions would be greater for deciduous species than for evergreen species.
  
  
  METHODS
  Root carbohydrate storage and organ biomass allometries were compared for juveniles of 20 savanna tree species of different leaf habit (nine evergreen, 11 deciduous) grown in two nutrient treatments for periods of 5 and 20 weeks (total dry mass of individual plants ranged from 0·003 to 258·724 g).
  
  
  RESULTS
  Deciduous species had greater root non-structural carbohydrate than evergreen species, and lower scaling exponents for leaf to root and stem to root partitioning than evergreen species. Across species, leaf to stem scaling was positively related, and stem to root scaling was negatively related to root carbohydrate concentration. Under lower nutrient supply, trees displayed increased partitioning to non-structural carbohydrate, and to roots and leaves over stems with increasing plant size, but this change did not differ between leaf habits.
  
  
  CONCLUSIONS
  Substantial unexplained variation in biomass allometry of woody species may be related to selection for resource conservation against environmental stresses, such as resource seasonality. Further differences in plant allometry could arise due to selection for different types of biomass allocation in response to different environmental stressors (e.g. fire vs. herbivory).
authors.affiliation: Resource Ecology Group, Wageningen University, PO Box 47, 6700 AA Wageningen, The Netherlands. kyle.tomlinson@wur.nl
authors.forename: Kyle W
authors.initials: KW
authors.lastname: Tomlinson
authors.forename: Frank
authors.initials: F
authors.lastname: van Langevelde
authors.forename: David
authors.initials: D
authors.lastname: Ward
authors.forename: Frans
authors.initials: F
authors.lastname: Bongers
authors.forename: Dulce Alves
authors.initials: DA
authors.lastname: da Silva
authors.forename: Herbert H T
authors.initials: HH
authors.lastname: Prins
authors.forename: Steven
authors.initials: S
authors.lastname: de Bie
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Sterck
mesh_terms: D018533:Biomass; D050260:Carbohydrate Metabolism; D008954:Models, Biological; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D012621:Seasons; D013312:Stress, Physiological; D014197:Trees / Q000254:growth & development* / Q000378:metabolism
keywords: Carbohydrate storage; leaf habit; nutrients; plant allocation theory; plant growth; savanna; trees