title: Nutrient acquisition, soil phosphorus partitioning and competition among trees in a lowland tropical rain forest.
abstract: We hypothesized that dinitrogen (N2)- and non-N2-fixing tropical trees would have distinct phosphorus (P) acquisition strategies allowing them to exploit different P sources, reducing competition. We measured root phosphatase activity and arbuscular mycorrhizal (AM) colonization among two N2- and two non-N2-fixing seedlings, and grew them alone and in competition with different inorganic and organic P forms to assess potential P partitioning. We found an inverse relationship between root phosphatase activity and AM colonization in field-collected seedlings, indicative of a trade-off in P acquisition strategies. This correlated with the predominantly exploited P sources in the seedling experiment: the N2fixer with high N2fixation and root phosphatase activity grew best on organic P, whereas the poor N2fixer and the two non-N2fixers with high AM colonization grew best on inorganic P. When grown in competition, however, AM colonization, root phosphatase activity and N2fixation increased in the N2fixers, allowing them to outcompete the non-N2fixers regardless of P source. Our results indicate that some tropical trees have the capacity to partition soil P, but this does not eliminate interspecific competition. Rather, enhanced P and N acquisition strategies may increase the competitive ability of N2fixers relative to non-N2fixers.
authors.affiliation: Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, MT, 59812, USA.
authors.forename: Megan K
authors.initials: MK
authors.lastname: Nasto
authors.affiliation: Institute at Brown for Environment and Society, Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, 02912, USA.
authors.forename: Brooke B
authors.initials: BB
authors.lastname: Osborne
authors.affiliation: MPG Ranch, Missoula, MT, 59803, USA.
authors.forename: Ylva
authors.initials: Y
authors.lastname: Lekberg
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, CA, 94305, USA.
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Asner
authors.affiliation: Department of Global Ecology, Carnegie Institution for Science, Stanford, CA, 94305, USA.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Balzotti
authors.affiliation: Institute at Brown for Environment and Society, Department of Ecology and Evolutionary Biology, Brown University, Providence, RI, 02912, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Porder
authors.affiliation: Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, 80303, USA.
authors.forename: Philip G
authors.initials: PG
authors.lastname: Taylor
authors.affiliation: Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, 80303, USA.
authors.forename: Alan R
authors.initials: AR
authors.lastname: Townsend
authors.affiliation: Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, MT, 59812, USA.
authors.forename: Cory C
authors.initials: CC
authors.lastname: Cleveland
mesh_terms: D003364:Costa Rica; D007887:Fabaceae / Q000502:physiology; D029586:Moraceae / Q000502:physiology; D038821:Mycorrhizae; D009586:Nitrogen Fixation; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D065947:Rainforest; D036226:Seedlings / Q000502:physiology; D012987:Soil / Q000737:chemistry*; D013045:Species Specificity; D014197:Trees / Q000502:physiology*; D014329:Tropical Climate
chemical_list: D012987:Soil; D010758:Phosphorus; D010744:Phosphoric Monoester Hydrolases
keywords: arbuscular mycorrhizal (AM) fungi; nitrogen fixation; nutrient acquisition strategies; phosphatase enzymes; phosphorus partitioning; tropical forest