Family- and population-level responses to atmospheric CO2 concentration: gas exchange and the allocation of C, N, and biomass in Plantago lanceolata (Plantaginaceae).

To ascertain the inheritance of responses to changing atmospheric CO(2) content, we partitioned response to elevated CO(2) in Plantago lanceolata between families and populations in 18 families in two populations. Plants were grown in 35 Pa and 71 Pa partial pressure of CO(2) (pCO(2)) in open-top chambers. We measured above- and belowground mass, carbon (C), nitrogen (N), hexose sugar, and gas exchange properties in both CO(2) treatments.

Response of soil biota to elevated atmospheric CO in poplar model systems.

We tested the hypotheses that increased belowground allocation of carbon by hybrid poplar saplings grown under elevated atmospheric CO would increase mass or turnover of soil biota in bulk but not in rhizosphere soil. Hybrid poplar saplings (Populus×euramericana cv. Eugenei) were grown for 5 months in open-bottom root boxes at the University of Michigan Biological Station in northern, lower Michigan.

Interacting effects of soil fertility and atmospheric CO on leaf area growth and carbon gain physiology in Populus×euramericana (Dode) Guinier.

Two important processes which may limit productivity gains in forest ecosystems with rising atmospheric CO are reduction in photosynthetic capacity following prolonged exposure to high CO and diminution of positive growth responses when soil nutrients, particularly N, are limiting. To examine the interacting effects of soil fertility and CO enrichment on photosynthesis and growth in trees we grew hybrid poplar (Populus × euramericana) for 158 d in the field at ambient and twice ambient CO and in soil with low or high N availability. We measured the timing and rate of canopy development, the seasonal dynamics of leaf level photosynthetic capacity, respiration, and N and carbohydrate concentration, and final above- and belowground dry weight.

Carbon-isotope discrimination by leaves of Flaveria species exhibiting different amounts of C3-and C 4-cycle co-function.

Carbon-isotope ratios were examined as δ(13)C values in several C3, C4, and C3-C4 Flaveria species, and compared to predicted δ(13)C, values generated from theoretical models. The measured δ(13)C values were within 4‰ of those predicted from the models. The models were used to identify factors that contribute to C3-like δ(13)C values in C3-C4 species that exhibit considerable C4-cycle activity.