Plant rhizospheric N processes: what we don't know and why we should care.

An improved understanding of the rapid nitrogen fluxes that occur in plant rhizospheres has not been adequately incorporated into the study of how soil N availability and plant N uptake control a number of important ecological processes. One reason for this is that current methods that measure N availability do not account for the rapid exchange of resources between roots and their closely associated microbial communities. In this paper, we review the tight interactions between roots and microbes and discuss why ignoring the significance of these interactions has led to unrepresentative estimates of N availability in intact plant communities and an incomplete understanding of the environmental factors that control plant-available N. We also explain why current standard methods to measure soil N availability do not account for important rhizospheric processes. Finally, we issue a challenge to develop new methods that will estimate soil N transformations in intact plant communities and offer some potential approaches that may help catalyze this effort.