title: Higher survival drives the success of nitrogen-fixing trees through succession in Costa Rican rainforests.
abstract: Trees capable of symbiotic nitrogen (N) fixation ('N fixers') are abundant in many tropical forests. In temperate forests, it is well known that N fixers specialize in early-successional niches, but in tropical forests, successional trends of N-fixing species are poorly understood. We used a long-term census study (1997-2013) of regenerating lowland wet tropical forests in Costa Rica to document successional patterns of N fixers vs non-fixers, and used an individual-based model to determine the demographic drivers of these trends. N fixers increased in relative basal area during succession. In the youngest forests, N fixers grew 2.5 times faster, recruited at a similar rate and were 15 times less likely to die as non-fixers. As succession proceeded, the growth and survival disparities decreased, whereas N fixer recruitment decreased relative to non-fixers. According to our individual-based model, high survival was the dominant driver of the increase in basal area of N fixers. Our data suggest that N fixers are successful throughout secondary succession in tropical rainforests of north-east Costa Rica, and that attempts to understand this success should focus on tree survival.
authors.affiliation: Department of Ecology, Evolution, and Environmental Biology, Columbia University, 1200 Amsterdam Ave, New York, NY, 10027, USA.
authors.forename: Duncan N L
authors.initials: DN
authors.lastname: Menge
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Connecticut, 75 N Eagleville Road, Unit 3043, Storrs, CT, 06269, USA.
authors.forename: Robin L
authors.initials: RL
authors.lastname: Chazdon
mesh_terms: D001419:Bacteria / Q000378:metabolism; D003364:Costa Rica; D009586:Nitrogen Fixation; D018547:Plant Stems / Q000502:physiology; D065947:Rainforest; D013045:Species Specificity; D014197:Trees / Q000502:physiology*
keywords: Pentaclethra macroloba; biogeochemistry; demography; growth; individual-based model; mortality; recruitment; tropical forest