Interactive effects of atmospheric CO2 and soil-N availability on fine roots of Populus tremuloides

he objective of this experiment was to understand how atmospheric carbon dioxide (CO2) and soil-nitrogen (N) availability influence Populus tremuloides fine-root growth and morphology. Soil-N availability may limit the growth response of forests to elevated CO2 and interact with atmospheric CO2 to alter litter quality and ecosystem carbon (C) and N cycling. We established a CO2 x N factorial field experiment and grew six genotypes of P. tremuloides for 2.5 growing seasons in 20 large open-top chamber/root- box experimental units at the University of Michigan Biological Station in northern lower Michigan (USA). In this paper we describe an integrated examination of how atmospheric CO2 and soil-N availability influence fine-root morphology, growth, mortality, and biomass. We also studied the relationship between root biomass and total soil respiration