Changes in the production and turnover of roots in forests and grasslands in response to rising atmospheric CO2
concentrations, elevated temperatures, altered precipitation, or nitrogen deposition could be a key link between
plant responses and longer-term changes in soil organic matter and ecosystem carbon balance. Here we summarize
the experimental observations, ideas, and new hypotheses developed in this area in the rest of this volume. Three
central questions are posed. Do elevated atmospheric CO2, nitrogen deposition, and climatic change alter the
dynamics of root production and mortality? What are the consequences of root responses to plant physiological
processes? What are the implications of root dynamics to soil microbial communities and the fate of carbon in soil?
Ecosystem-level observations of root production and mortality in response to global change parameters are just
starting to emerge. The challenge to root biologists is to overcome the profound methodological and analytical
problems and assemble a more comprehensive data set with sufficient ancillary data that differences between
ecosystems can be explained. The assemblage of information reported herein on global patterns of root turnover,
basic root biology that controls responses to environmental variables, and new observations of root and associated
microbial responses to atmospheric and climatic change helps to sharpen our questions and stimulate new research
approaches. New hypotheses have been developed to explain why responses of root turnover might differ in
contrasting systems, how carbon allocation to roots is controlled, and how species differences in root chemistry
might explain the ultimate fate of carbon in soil. These hypotheses and the enthusiasm for pursuing them are based
on the firm belief that a deeper understanding of root dynamics is critical to describing the integrated response
of ecosystems to global change.