title: Sodium co-limits and catalyzes macronutrients in a prairie food web.
abstract: Nitrogen and phosphorus frequently limit terrestrial plant production, but have a mixed record in regulating the abundance of terrestrial invertebrates. We contrasted four ways that Na could interact with an NP fertilizer to shape the plants and invertebrates of an inland prairie. We applied NP and Na to m2plots in a factorial design. Aboveground invertebrate abundance was independently co-limited by NaCl and NP, but with +NP plots supporting more individuals. We suggest the disparity arises because NP enhanced plant height by 35% (1 SD) over controls, providing both food and habitat, whereas NaCl provides only food. Belowground invertebrates showed evidence of serial co-limitation, where NaCl additions alone were ineffectual, but catalyzed access to NP. This suggests the increased belowground food availability in NP plots increased Na demand. Na and NP supply rates vary with climate, land use, and with inputs like urine. The co-limitation and catalysis of N and P by Na thus has the potential for predicting patterns of abundance and diversity across spatial scales.
authors.affiliation: Graduate Program in EEB, Department of Biology, University of Oklahoma, Norman, Oklahoma, 73019, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Kaspari
authors.affiliation: Graduate Program in EEB, Department of Biology, University of Oklahoma, Norman, Oklahoma, 73019, USA.
authors.forename: Karl A
authors.identifier: http://orcid.org/0000-0002-2628-5003
authors.initials: KA
authors.lastname: Roeder
authors.affiliation: Graduate Program in EEB, Department of Biology, University of Oklahoma, Norman, Oklahoma, 73019, USA.
authors.forename: Brittany
authors.initials: B
authors.lastname: Benson
authors.affiliation: Graduate Program in EEB, Department of Biology, University of Oklahoma, Norman, Oklahoma, 73019, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Weiser
authors.affiliation: Rocky Mountain Biological Laboratory, PO Box 519, Crested Butte, Colorado, 81224, USA.|Center for Macroecology, Evolution, and Climate, Natural History Museum, University of Copenhagen, Copenhagen, 2100, Denmark.
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Sanders
mesh_terms: D000818:Animals; D017753:Ecosystem; D020387:Food Chain; D065948:Grassland; D009584:Nitrogen; D010758:Phosphorus; D012964:Sodium / Q000032:analysis*
chemical_list: D010758:Phosphorus; D012964:Sodium; D009584:Nitrogen
keywords: grassland food webs; nitrogen; nutrient limitation; phosphorus; sodium