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

Document Type

Article

Publication Date

12-2004

Publication Title

Global Change Biology

Volume

10

Issue

12

First page number:

2121

Last page number:

2138

Abstract

The magnitude of changes in carboxylation capacity in dominant plant species under long-term elevated CO2 exposure (elevated pCa) 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 (49.5–57.1 Pa), 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 pCa, 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 pCa 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 Vcmax 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 CO2 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.

Keywords

Deciduous forests; Deserts; Downregulation; Elevated CO2; Free-Air CO2 Enrichment (FACE); Grasslands; Leaf carboxylation capacity; Leaf nitrogen; Nitrogen allocation to RuBP carboxylase enzyme; Photosynthesis-nitrogen relationships; Photosynthetic nitrogen-use efficiency; pine forests; Plant functional groups

Disciplines

Plant Biology

Language

English

Publisher Citation

Ellsworth, D. S., Reich, P. B., Naumburg, E. S., Koch, G. W., Kubiske, M. E. and Smith, S. D. (2004), Photosynthesis, carboxylation and leaf nitrogen responses of 16 species to elevated pCO2 across four free-air CO2 enrichment experiments in forest, grassland and desert. Global Change Biology, 10: 2121–2138. doi: 10.1111/j.1365-2486.2004.00867.x

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