title: Soil nutrients influence spatial distributions of tropical tree species.
abstract: The importance of niche vs. neutral assembly mechanisms in structuring tropical tree communities remains an important unsettled question in community ecology [Bell G (2005) Ecology 86:1757-1770]. There is ample evidence that species distributions are determined by soils and habitat factors at landscape (<10(4) km(2)) and regional scales. At local scales (<1 km(2)), however, habitat factors and species distributions show comparable spatial aggregation, making it difficult to disentangle the importance of niche and dispersal processes. In this article, we test soil resource-based niche assembly at a local scale, using species and soil nutrient distributions obtained at high spatial resolution in three diverse neotropical forest plots in Colombia (La Planada), Ecuador (Yasuni), and Panama (Barro Colorado Island). Using spatial distribution maps of >0.5 million individual trees of 1,400 species and 10 essential plant nutrients, we used Monte Carlo simulations of species distributions to test plant-soil associations against null expectations based on dispersal assembly. We found that the spatial distributions of 36-51% of tree species at these sites show strong associations to soil nutrient distributions. Neutral dispersal assembly cannot account for these plant-soil associations or the observed niche breadths of these species. These results indicate that belowground resource availability plays an important role in the assembly of tropical tree communities at local scales and provide the basis for future investigations on the mechanisms of resource competition among tropical tree species.
authors.affiliation: Department of Plant Biology, University of Illinois at Urbana-Champaign, 505 South Goodwin Avenue, Urbana, IL 61801, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: John
authors.forename: James W
authors.initials: JW
authors.lastname: Dalling
authors.forename: Kyle E
authors.initials: KE
authors.lastname: Harms
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Yavitt
authors.forename: Robert F
authors.initials: RF
authors.lastname: Stallard
authors.forename: Matthew
authors.initials: M
authors.lastname: Mirabello
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Hubbell
authors.forename: Renato
authors.initials: R
authors.lastname: Valencia
authors.forename: Hugo
authors.initials: H
authors.lastname: Navarrete
authors.forename: Martha
authors.initials: M
authors.lastname: Vallejo
authors.forename: Robin B
authors.initials: RB
authors.lastname: Foster
mesh_terms: D017753:Ecosystem; D006863:Hydrogen-Ion Concentration; D011157:Population Dynamics; D012987:Soil / Q000032:analysis*; D013020:South America; D014197:Trees / Q000502:physiology*; D014329:Tropical Climate
chemical_list: D012987:Soil