title: Nutrient foraging strategies are associated with productivity and population growth in forest shrubs.
abstract: Temperate deciduous forest understoreys are experiencing widespread changes in community composition, concurrent with increases in rates of nitrogen supply. These shifts in plant abundance may be driven by interspecific differences in nutrient foraging (i.e. conservative vs. acquisitive strategies) and, thus, adaptation to contemporary nutrient loading conditions. This study sought to determine if interspecific differences in nutrient foraging could help explain patterns of shrub success and decline in eastern North American forests.
  
  
  
  Using plants grown in a common garden, fine root traits associated with nutrient foraging were measured for six shrub species. Traits included the mean and skewness of the root diameter distribution, specific root length (SRL), C:N ratio, root tissue density, arbuscular mycorrhizal colonization and foraging precision. Above- and below-ground productivity were also determined for the same plants, and population growth rates were estimated using data from a long-term study of community dynamics. Root traits were compared among species and associations among root traits, measures of productivity and rates of population growth were evaluated.
  
  
  
  Species fell into groups having thick or thin root forms, which correspond to conservative vs. acquisitive nutrient foraging strategies. Interspecific variation in root morphology and tissue construction correlated with measures of productivity and rates of cover expansion. Of the four species with acquisitive traits, three were introduced species that have become invasive in recent decades, and the fourth was a weedy native. In contrast, the two species with conservative traits were historically dominant shrubs that have declined in abundance in eastern North American forests.
  
  
  
  In forest understoreys of eastern North America, elevated nutrient availability may impose a filter on species success in addition to above-ground processes such as herbivory and overstorey canopy conditions. Shrubs that have root traits associated with rapid uptake of soil nutrients may be more likely to increase in abundance, while species without such traits may be less likely to keep pace with more productive species.
authors.affiliation: Department of Ecology, Evolution, and Natural Resources, Rutgers, The State University of New Jersey, 14 College Farm Road, New Brunswick, NJ 08901, USA.|Department of Biology, Bryn Mawr College, 101 North Merion Avenue, Bryn Mawr, PA 19010, USA.
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Caplan
authors.affiliation: Department of Biology, University of Mississippi, 30 University Avenue, University, MS 38677, USA.
authors.forename: Bram W G
authors.initials: BWG
authors.lastname: Stone
authors.affiliation: Department of Ecology, Evolution, and Natural Resources, Rutgers, The State University of New Jersey, 14 College Farm Road, New Brunswick, NJ 08901, USA.
authors.forename: Cara A
authors.initials: CA
authors.lastname: Faillace
authors.affiliation: Department of Ecology, Evolution, and Natural Resources, Rutgers, The State University of New Jersey, 14 College Farm Road, New Brunswick, NJ 08901, USA.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Lafond
authors.affiliation: Department of Ecology, Evolution, and Natural Resources, Rutgers, The State University of New Jersey, 14 College Farm Road, New Brunswick, NJ 08901, USA.|Rutgers Pinelands Field Station, PO Box 206, New Lisbon, NJ 08064, USA.
authors.forename: Joni M
authors.initials: JM
authors.lastname: Baumgarten
authors.affiliation: Department of Biology, Bryn Mawr College, 101 North Merion Avenue, Bryn Mawr, PA 19010, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Mozdzer
authors.affiliation: Rutgers Pinelands Field Station, PO Box 206, New Lisbon, NJ 08064, USA.
authors.forename: John
authors.initials: J
authors.lastname: Dighton
authors.affiliation: Department of Biological Sciences, Eastern Illinois University, 600 Lincoln Avenue, Charleston, IL 61920, USA.
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Meiners
authors.affiliation: Department of Ecology, Evolution, and Natural Resources, Rutgers, The State University of New Jersey, 14 College Farm Road, New Brunswick, NJ 08901, USA.
authors.forename: Jason C
authors.initials: JC
authors.lastname: Grabosky
authors.affiliation: Department of Ecology, Evolution, and Natural Resources, Rutgers, The State University of New Jersey, 14 College Farm Road, New Brunswick, NJ 08901, USA.
authors.forename: Joan G
authors.initials: JG
authors.lastname: Ehrenfeld
mesh_terms: D065928:Forests; D058865:Introduced Species; D019684:Magnoliopsida / Q000254:growth & development / Q000502:physiology*; D009515:New Jersey; D009584:Nitrogen / Q000378:metabolism*; D011158:Population Growth; D014197:Trees / Q000254:growth & development / Q000502:physiology
chemical_list: D009584:Nitrogen
keywords: Below-ground dynamics; deciduous forest understorey; foraging strategies; functional traits; nutrient acquisition; rhizosphere; root economics spectrum; root morphology; woody shrubs