Photosynthesis, carboxylation and leaf nitrogen responses of 16 species to elevated pCO2 across four free-air CO2 enrichment experiments in forest, grassland and desert

David S. Ellsworth, Peter B. Reich, Elke S. Naumburg, George W. Koch, Mark E. Kubiske, Stan D. Smith

Research output: Contribution to journalArticlepeer-review

259 Scopus citations


The magnitude of changes in carboxylation capacity in dominant plant species under long-term elevated CO2 exposure (elevated pC a) directly impacts ecosystem CO2 assimilation from the atmosphere. We analyzed field CO2 response curves of 16 C3 species of different plant growth forms in favorable growth conditions in four free-air CO2 enrichment (FACE) experiments in a pine and deciduous forest, a grassland and a desert. Among species and across herb, tree and shrub growth forms there were significant enhancements in CO2 assimilation (A) by + 40 ± 5% in elevated pCa (49.5-57.1Pa), although there were also significant reductions in photosynthetic capacity in elevated pCa in some species. Photosynthesis at a common pCa (Aa) was significantly reduced in five species growing under elevated pC a, while leaf carboxylation capacity (Vcmax) was significantly reduced by elevated pCa in seven species (change of -19 ±3% among these species) across different growth forms and FACE sites. Adjustments in Vcmax with elevated pC a were associated with changes in leaf N among species, and occurred in species with the highest leaf N. Elevated pCa treatment did not affect the mass-based relationships between A or V cmax and N, which differed among herbs, trees and shrubs. Thus, effects of elevated pCa on leaf C assimilation and carboxylation capacity occurred largely through changes in leaf N, rather than through elevated pCa effects on the relationships themselves. Maintenance of leaf carboxylation capacity among species in elevated pCa at these sites depends on maintenance of canopy N stocks, with leaf N depletion associated with photosynthetic capacity adjustments. Since CO2 responses can only be measured experimentally on a small number of species, understanding elevated CO 2 effects on canopy Nm and Na will greatly contribute to an ability to model responses of leaf photosynthesis to atmospheric CO2 in different species and plant growth forms.

Original languageEnglish (US)
Pages (from-to)2121-2138
Number of pages18
JournalGlobal change biology
Issue number12
StatePublished - Dec 2004


  • Downregulation
  • Elevated CO
  • Free air CO enrichment
  • Leaf carboxylation capacity
  • Leaf nitrogen
  • Nitrogen allocation to RuBP carboxylase enzyme
  • Photosynthesis-nitrogen relationships
  • Photosynthetic nitrogen-use efficiency
  • Plant functional groups

ASJC Scopus subject areas

  • Global and Planetary Change
  • Environmental Chemistry
  • Ecology
  • General Environmental Science


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