How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

A Tropical Tree's Response to Modestly Elevated Atmospheric CO2
Rasineni, G.K., Guha, A. and Reddy, A.R. 2011. Responses of Gmelina arborea, a tropical deciduous tree species, to elevated atmospheric CO2: Growth, biomass productivity and carbon sequestration efficacy. Plant Science 181: 428-438.

The authors write that "carbon sequestration as a climate change mitigation policy has received significant attention over the past several years," and they note that planting young fast-growing trees to absorb excess atmospheric CO2 "has recently gained potentiality, leading to identification of tree species with high CO2 sequestration capacity."

What was done
As their contribution to this endeavor, Rasineni et al. grew well-watered-and-fertilized five-week-old fast-growing Gmelina arborea trees out-of-doors at the University of Hyderabad, India, within open-top chambers maintained at ambient and ambient+100 ppm atmospheric CO2 concentrations throughout the 120 days of that region's spring and summer seasons, while they periodically made numerous measurements of the trees' physical properties and physiological prowess.

What was learned
At the conclusion of the spring and summer growing seasons, the trees in the modestly-elevated CO2 chambers exhibited net photosynthetic rates that were 38% greater than those of the trees growing in ambient air; and aided by a significant CO2-induced reduction in leaf transpiration rates, the mean instantaneous water-use efficiency of the leaves of the CO2-enriched trees was 87% greater than that of the ambient-treatment trees. And as a result of these CO2-induced plant physiological benefits, the above-ground biomass of the CO2-enriched trees at the end of the growing season was found to be 45% greater than that of the trees growing in ambient air, while their total biomass (above and below ground) was 53% higher.

What it means
In discussing their findings, Rasineni et al. note that elevated atmospheric CO2 "persistently enhanced all the growth characteristics in Gmelina, including plant height, number of branches, internodes, internodal distance, aerial biomass and total plant biomass." And they suggest that "high sink demand and better growth dynamics" are what led to the huge sustained increase in carbon sequestration in the tropical deciduous tree. Thus, they conclude that their findings point to the likelihood that "there are management options for creating short-rotation deciduous tree plantations to achieve increased sequestration of carbon in a future elevated CO2 environment."

Reviewed 30 November 2011