Editorial
CO2 Sequestration: Our Father was Right … Probably: Recent landmark studies published in Science suggest that the terrestrial biosphere is removing CO2 from the atmosphere at a rate significantly faster than anyone, except our father, considered even remotely possible only a few short years ago.

Journal Reviews
A Means for Biology to Influence Climate: This study demonstrates that certain biogenic gases experience gas-to-particle conversions that result in the production of enhanced numbers of cloud condensation nuclei that can lead to the production of more clouds that reflect additional solar radiation back to space and counter global warming.

CO2 Sequestration by Tropical Forests: Long-term records of hundreds of plots of mature tropical forest reveal that tropical forest biomass is increasing at such a rate that Central and South America alone can account for approximately 40% of the world's missing carbon sink.

CO2 Sequestration in North America: Observation-driven calculations suggest that there exists a huge terrestrial carbon sink in North America that yearly sequesters all of the CO2 annually produced by the burning of fossil fuels in both the United States and Canada.

Evidence of Our Ignorance: Two reviews of the state of our knowledge of past millennial-scale climate oscillations reveal our lack of understanding of the mechanisms that may be responsible for them, highlighting the danger of believing too strongly that we know where earth's climate is headed in the next century or two.

Effects of Elevated CO2 on Photosynthetic Acclimation in Wheat: Spring wheat grown in open-field plots receiving elevated levels of atmospheric CO2 supplied by FACE technology exhibited photosynthetic acclimation by reducing leaf rubisco and nitrogen levels.  However, greater final yields were still produced, due to a CO2-induced increase in the efficiency of leaf photosynthetic nitrogen use.

Photosynthetic Acclimation to Elevated CO2 in Three Chalk Grassland Species: Three perennial plants (two forbs and a grass) common to chalk grassland swards of Europe exhibited varying degrees of photosynthetic down regulation in a free-air atmospheric CO2 enrichment (FACE) experiment.  Following a simulated grazing event, however, all three species displayed 30 to 40% increases in net photosynthesis when grown at elevated CO2.

Influence of Carbohydrate Utilization on Photosynthetic Acclimation of Ryegrass to Elevated CO2: Perennial ryegrass grown in FACE plots on farmland in Switzerland exhibited photosynthetic acclimation at elevated CO2 only when grown at low soil nitrogen.  And after cutting the grass, even this acclimation disappeared, indicating that acclimation is not a direct consequence of atmospheric CO2 enrichment but rather an indirect effect of low soil nitrogen limiting plant sink development.

Influence of Carbohydrates on Photosynthetic Acclimation of Rice: Rice plants grown at atmospheric CO2 concentrations of 350 and 700 ppm for 34 days had their CO2 concentrations switched for 10 days.  Plants that were grown at elevated CO2 were sink-limited in their growth and displayed signs of photosynthetic acclimation, but upon switching them to ambient CO2, these plants displayed an up regulation of leaf rubisco and a decrease in leaf carbohydrate content in response to the rapid adjustment in source strength.

Influence of Nitrogen Supply on Photosynthetic Acclimation of Wheat to Elevated CO2: Wheat plants grown in pots exhibited photosynthetic down regulation when supplied with a low fixed amount of nitrogen; and elevated CO2 exacerbated this acclimation.  In contrast, hydroponically-grown wheat that received a gradually increasing nutrient supply, which became ever larger with increasing plant size, exhibited no signs of photosynthetic down regulation when grown at elevated CO2 even at low nitrogen availability.  These observations led the authors to develop a more comprehensive conceptual framework for photosynthetic acclimation than has heretofore been elucidated.

Effects of a Naturally High CO2 Source on a Venezuelan Herb and Tree: Studies of herbs and trees growing near natural CO2 springs in Venezuela showed that a tripling of the air's CO2 content could increase the water-use efficiency of the herbs by a factor of 4 and that of the trees by a factor of 20.  In the dry season, this CO2-conferred advantage allowed the plants near the springs to continue to grow and sequester carbon, while those exposed to ambient air some distance away actually lost carbon to the air.