title: Does species diversity limit productivity in natural grassland communities?
abstract: Theoretical analyses and experimental studies of synthesized assemblages indicate that under particular circumstances species diversity can enhance community productivity through niche complementarity. It remains unclear whether this process has important effects in mature natural ecosystems where competitive feedbacks and complex environmental influences affect diversity-productivity relationships. In this study, we evaluated diversity-productivity relationships while statistically controlling for environmental influences in 12 natural grassland ecosystems. Because diversity-productivity relationships are conspicuously nonlinear, we developed a nonlinear structural equation modeling (SEM) methodology to separate the effects of diversity on productivity from the effects of productivity on diversity. Meta-analysis was used to summarize the SEM findings across studies. While competitive effects were readily detected, enhancement of production by diversity was not. These results suggest that the influence of small-scale diversity on productivity in mature natural systems is a weak force, both in absolute terms and relative to the effects of other controls on productivity.
authors.affiliation: U.S. Geological Survey, Lafayette, LA 70506, USA. jim_grace@usgs.gov
authors.forename: James B
authors.initials: JB
authors.lastname: Grace
authors.forename: T
authors.initials: T
authors.lastname: Michael Anderson
authors.forename: Melinda D
authors.initials: MD
authors.lastname: Smith
authors.forename: Eric
authors.initials: E
authors.lastname: Seabloom
authors.forename: Sandy J
authors.initials: SJ
authors.lastname: Andelman
authors.forename: Gayna
authors.initials: G
authors.lastname: Meche
authors.forename: Evan
authors.initials: E
authors.lastname: Weiher
authors.forename: Larry K
authors.initials: LK
authors.lastname: Allain
authors.forename: Heli
authors.initials: H
authors.lastname: Jutila
authors.forename: Mahesh
authors.initials: M
authors.lastname: Sankaran
authors.forename: Johannes
authors.initials: J
authors.lastname: Knops
authors.forename: Mark
authors.initials: M
authors.lastname: Ritchie
authors.forename: Michael R
authors.initials: MR
authors.lastname: Willig
mesh_terms: D044822:Biodiversity; D018533:Biomass; D004777:Environment; D016013:Likelihood Functions; D008962:Models, Theoretical; D017711:Nonlinear Dynamics; D006109:Poaceae / Q000502:physiology*