This Special Issue of New Phytologist contains the latest information and new ideas about how root dynamics might alter in the face of a globally changing environment. The importance of this topic is clear: 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.

The introductory review (Norby & Jackson, 2000), which draws together the different contributions to the volume, asks three central questions:

[bull ] Do elevated atmospheric CO2, nitrogen deposition, and climatic change alter the dynamics of root production and mortality?

[bull ] How do physiological responses of roots to global change factors impact whole-plant and ecosystem metabolism?

[bull ] What are the implications of root dynamics for soil microbial communities and the fate of carbon in soil?

Ecosystem-level observations of root production and mortality in response to global change factors 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 from which ecosystem responses can be explained. The commissioned reviews and research papers in this volume attempt to meet that challenge. Following the introductory review, three papers provide a framework for subsequent analyses by presenting a global perspective on root turnover, a review of morphological and physiological attributes of roots, and a discussion of concepts of carbon allocation in plants. This is followed by a series of papers describing experimental studies on the effects of elevated CO2 and climatic change in various ecosystems. Three papers consider the physiological responses of roots to global change factors, followed by three papers reviewing mycorrhizal interactions and soil biology, and the implications for carbon sequestration in soil. The final paper returns to a global perspective with an analysis of how roots are handled in models of global change. Throughout these articles there is information on topics such as methodology for studying root dynamics, the major gaps in our knowledge, and the idea that leaves are a good analogy for roots.