CO \u3c inf\u3e 2 enrichment and warming of the atmosphere enhance both productivity and mortality of maple tree fine roots

• Fine roots are the key link for plant water and nutrient uptake, soil carbon (C) input and soil microbial activity in forest ecosystems, and play a critical role in regulating ecosystem C balance and its response to global change. • Red maple (Acer rubrum) and sugar maple (Acer saccharum) seedlings were grown for four growing seasons in open-top chambers and exposed to ambient or elevated carbon dioxide concentration [CO2] in combination with ambient or elevated temperature. Fine-root production and mortality were monitored using minirhizotrons, and root biomass was determined from soil cores. • Both elevated [CO2] and temperature significantly enhanced production and mortality of fine roots during spring and summer of 1996. At the end of the experiment in September 1997, fine root biomass was significantly lower in elevated temperature chambers, but there were no effects of elevated [CO2] or the interactions between elevated [CO2] and temperature. • Deciduous trees have dynamic root systems, and their activity can be enhanced by CO2 enrichment and climatic warming. Static measures of root response, such as soil core data, obscure the dynamic nature, which is critical for understanding the response of forest C cycling to global change. © New Phytologist (2004)