Photosynthetic acclimation of overstory Populus tremuloides and understory Acer saccharum to elevated atmospheric CO2 concentration: interactions with shade and soil nitrogen

Abstract

We exposed Populus tremuloides Michx. and Acer saccharum Marsh. to a factorial combination of ambient and elevated atmospheric CO2 concentrations ([CO2]) and high-nitrogen (N) and low-N soil treatments in open-top chambers for 3 years. Our objective was to compare photosynthetic acclimation to elevated [CO2] between species of contrasting shade tolerance, and to determine if soil N or shading modify the acclimation response. Sun and shade leaf responses to elevated [CO2] and soil N were compared between upper and lower canopy leaves of P. tremuloides and between A. saccharum seedlings grown with and without shading by P. tremuloides. Both species had higher leaf N concentrations and photosynthetic rates in high-N soil than in low-N soil, and these characteristics were higher for P. tremuloides than for A. saccharum. Electron transport capacity (Jmax) and carboxylation capacity (Vcmax) generally decreased with atmospheric CO2 enrichment in all 3 years of the experiment, but there was no evidence that elevated [CO2] altered the relationship between them. On a leaf area basis, both Jmax and Vcmax acclimated to elevated [CO2] more strongly in shade leaves than in sun leaves of P. tremuloides. However, the apparent [CO2] x shade interaction was largely driven by differences in specific leaf area (m2 g-1) between sun and shade leaves. In A. saccharum, photosynthesis acclimated more strongly to elevated [CO2] in sun leaves than in shade leaves on both leaf area and mass bases. We conclude that trees rooted freely in the ground can exhibit photosynthetic acclimation to elevated [CO2], and the response may be modified by light environment. The hypothesis that photosynthesis acclimates more completely to elevated [CO2] in shade-tolerant species than in shade-intolerant species was not supported.

Seedling survival in a northern temperate forest understory is increased by elevated atmospheric carbon dioxide and atmospheric nitrogen deposition

“…Studies have found that soil fertility can restrain the plant growth response to CO 2 enrichment (Kubiske et al, 1997;Curtis et al, 2000;Oren et al, 2001;Tissue et al, 2001). Our results further suggest that soil N availability may mediate the acclimation response of photosynthesis to CO 2 enrichment, with low N sites acclimating more to elevated CO 2 than sites having higher fertility (Medlyn et al, 2000, Kubiske et al, 2002. This suggests that the response of ecosystems to enriched atmospheric [CO 2 ] will depend on the nutrient availability of the ecosystem (Saxe et al, 1998;Kö rner, 2000;McMurtrie et al, 2001;Spinnler et al, 2002).…”

Linking photosynthesis and leaf N allocation under future elevated CO2and climate warming inEucalyptus globulus

“…It has been hypothesized that within-canopy differences in the light environment may influence the response to eC (Kubiske et al , 2002) as a result of light-driven differences in photosynthetic N allocation (Evans, 1993; Hikosaka and Terashima, 1995). Although lower canopy leaves showed weaker responses to eC and eT relative to upper canopy leaves, there were no significant canopy×treatment interactions for any of the measured parameters (except for a significant canopy×temperature effect on LMA), probably due to the open crown structure in Eucalyptus species.…”

Global Change Effects on Plant Chemical Defenses against Insect Herbivores

“…For example, the inclusion of insect herbivory in a growth chamber experiment altered the lifetime fitness response of Arabidopsis thaliana to elevated CO 2 (Bidart‐Bouzat et al 2005); in other words, herbivory was found to either suppressed or decreased plant fitness enhancements induced by elevated CO 2 per se . Other studies have also demonstrated that plant responses to elevated CO 2 can be influenced by plant‐plant competition, temperature, light, water stress, and nutrients (Bazzaz and Miao 1993; Bazzaz et al 1995; Zhang and Lechowicz 1995; Kellomaki and Vaisanen 1997; Curtis and Wang 1998; Andalo et al 2001; Kubiske et al 2002; Wullschleger et al 2002).…”