title: No evidence that boron influences tree species distributions in lowland tropical forests of Panama.
abstract: It was recently proposed that boron might be the most important nutrient structuring tree species distributions in tropical forests. Here we combine observational and experimental studies to test this hypothesis for lowland tropical forests of Panama. Plant-available boron is uniformly low in tropical forest soils of Panama and is not significantly associated with any of the > 500 species in a regional network of forest dynamics plots. Experimental manipulation of boron supply to seedlings of three tropical tree species revealed no evidence of boron deficiency or toxicity at concentrations likely to occur in tropical forest soils. Foliar boron did not correlate with soil boron along a local scale gradient of boron availability. Fifteen years of boron addition to a tropical forest increased plant-available boron by 70% but did not significantly change tree productivity or boron concentrations in live leaves, wood or leaf litter. The annual input of boron in rainfall accounts for a considerable proportion of the boron in annual litterfall and is similar to the pool of plant-available boron in the soil, and is therefore sufficient to preclude boron deficiency. We conclude that boron does not influence tree species distributions in Panama and presumably elsewhere in the lowland tropics.
authors.affiliation: Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Panama.
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Turner
authors.affiliation: Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Panama.|Department of Plant Biology, University of Illinois, Urbana, IL, 61801, USA.
authors.forename: Paul-Camilo
authors.initials: PC
authors.lastname: Zalamea
authors.affiliation: Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Panama.
authors.forename: Richard
authors.initials: R
authors.lastname: Condit
authors.affiliation: Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Panama.
authors.forename: Klaus
authors.initials: K
authors.lastname: Winter
authors.affiliation: Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Panama.
authors.forename: S Joseph
authors.initials: SJ
authors.lastname: Wright
authors.affiliation: Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Ancon, Panama.|Department of Plant Biology, University of Illinois, Urbana, IL, 61801, USA.
authors.forename: James W
authors.initials: JW
authors.lastname: Dalling
mesh_terms: D018533:Biomass; D001895:Boron / Q000494:pharmacology*; D065928:Forests; D010176:Panama; D011891:Rain; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development; D012987:Soil / Q000737:chemistry; D013045:Species Specificity; D014197:Trees / Q000187:drug effects / Q000502:physiology*; D014329:Tropical Climate
chemical_list: D012987:Soil; D001895:Boron
keywords: Barro Colorado Island; Mehlich-III extraction; boron (B); ecosystem budget; hot-water extraction; nutrient cycling; species distribution; tropical forest