title: Tight coupling of leaf area index to canopy nitrogen and phosphorus across heterogeneous tallgrass prairie communities.
abstract: Nitrogen (N) and phosphorus (P) are limiting nutrients for many plant communities worldwide. Foliar N and P along with leaf area are among the most important controls on photosynthesis and hence productivity. However, foliar N and P are typically assessed as species level traits, whereas productivity is often measured at the community scale. Here, we compared the community-level traits of leaf area index (LAI) to total foliar nitrogen (TFN) and total foliar phosphorus (TFP) across nearly three orders of magnitude LAI in grazed and ungrazed tallgrass prairie in north-eastern Kansas, USA. LAI was strongly correlated with both TFN and TFP across communities, and also within plant functional types (grass, forb, woody, and sedge) and grazing treatments (bison or cattle, and ungrazed). Across almost the entire range of LAI values and contrasting communities, TFN:TFP ratios indicated co-limitation by N and P in almost all communities; this may further indicate a community scale trend of an optimal N and P allocation per unit leaf area for growth. Previously, results from the arctic showed similar tight relationships between LAI:TFN, suggesting N is supplied to canopies to maximize photosynthesis per unit leaf area. This tight coupling between LAI, N, and P in tallgrass prairie suggests a process of optimal allocation of N and P, wherein LAI remains similarly constrained by N and P despite differences in species composition, grazing, and canopy density.
authors: Division of Biology, Kansas State University, Manhattan, KS, USA.|Department of Plant Science, Pennsylvania State University, University Park, PA, USA.
authors: Anne E
authors: AE
authors: Klodd
authors: Division of Biology, Kansas State University, Manhattan, KS, USA. nippert@ksu.edu.
authors: Jesse B
authors: JB
authors: Nippert
authors: Division of Biology, Kansas State University, Manhattan, KS, USA.|Department of Environmental Science, University of Virginia, Charlottesville, VA, USA.
authors: Zak
authors: Z
authors: Ratajczak
authors: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.
authors: Hazel
authors: H
authors: Waring
authors: Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield, S10 2TN, UK.
authors: Gareth K
authors: GK
authors: Phoenix
mesh_terms: D000818:Animals; D002417:Cattle; D065948:Grassland; D009584:Nitrogen; D010758:Phosphorus; D010788:Photosynthesis; D018515:Plant Leaves
chemical_list: D010758:Phosphorus; D009584:Nitrogen
keywords: Co-limitation; Fire; Grassland; Grazers; Nutrients