Td. Lee et al., Leaf gas exchange responses of 13 prairie grassland species to elevated CO2 and increased nitrogen supply, NEW PHYTOL, 150(2), 2001, pp. 405-418
Leaf gas exchange responses to elevated CO2 and N are presented for 13 pere
nnial species, representing four functional groups: C-3 grasses, C-4 grasse
s, legumes, and nonleguminous forbs. Understanding how CO2 and N effects in
teract is important to predict plant community response to global change.
Plants were field-grown in monoculture under current ambient and elevated (
560 mu mol mol(-1)) CO2 concentrations (free-air CO2 enrichment), in combin
ation with soil N treatments, for two growing seasons.
All species, regardless of functional group, showed pronounced photosynthet
ic acclimation to elevated CO2, resulting in minimal stimulation of photosy
nthesis (A) averaging +15% in C-3 grasses, +8% in forbs, +7% in legumes and
-2% in C-4 grasses. The effects of CO, and soil N supply did not interact
for any leaf traits measured. Elevated CO2 consistently decreased stomatal
conductance (g(s)) leading to 40% increase in A/g(s).
This substantial acclimation of photosynthesis was greater in magnitude tha
n in most field studies, and was associated with the combined effects of de
creased g(s) and decreased leaf N concentrations in response to growth unde
r elevated CO2.