Changing CO_2 promises surprising changes in plant communities

摘要

High carbon dioxide (CO_2) levels - an important contributor to global warming - have changed the botanical composition of the worlds grasslands, farms, and urban landscapes by increasing the growth, reproduction, or survival of some species more thanothers. The greatest changes may have already happened, so studies of past effects offer clues to future surprises. Wayne Polley and Philip Fay, ecologists at the ARS Grassland Soil and Water Research Laboratory in Temple, Texas, US, offer an unprecedented look into the past and future. "Time tunnels" are used to expose a mix of tall prairie grasses and other plants to a gradient of CO_2 levels, from the Ice Age to 2050 A.D. They use the greenhouselike plastic-covered tunnels instead of open-top outdoor chambers in which plants are exposed to just one level of CO_2 per chamber.