Summary of Plant Physiology and Growth

Summary of the influence of elevated CO2 on C 3 and C 4 plant communities. Symbols indicate a large CO2 response (++), a moderate response (+), or a negligible response (0).

 

Community

 

C3

C4

Gross CO2 assimilation

++

+

Net CO2 assimilation

++

+

Shoot density

++

0

Shoot biomass

++

0

Root biomass

++

0

Root productivity

++

0

ur long-term (17 y) investigations have focused on plant physiological processes and growth in response to elevated CO2. As reported above, photosynthesis and growth in the C 3 plant community consistently increased in response to elevated CO2, particularly in years of high rainfall and low salinity. These responses were absent or greatly diminished in the C 4 community exposed to elevated CO2 (Table at right). A focus of our recent work has been to understand the fate the 'excess' carbon assimilated by the C 3 plant community, much of which has been allocated belowground. In the next section we report on changes in soil heterotrophic processes that return carbon to the atmosphere. In the final section, we report on changes in carbon storage and the status of the carbon budget.


 Research Questions