The cryptic nature of soil makes assessing root turnover extremely difficult.  Radiocarbon techniques have indicated multi-year lifespans for fine roots, whereas minirhizotron images indicate much shorter turnovers.  Accounting for root order may help to reconcile these disparate measurements. Seasonal variability in the ¹³C content of recently fixed plant sugars suggests that ¹³C measurements on fine roots could be an additional tool to examine root turnover over seasonal time spans.  These measurements could help to constrain turnover times derived from other measurement techniques.  Here, ¹³C content in a temperate forest of foliage, phloem sap, roots growing through root screens, and roots of different orders were compared to assess the usefulness of this technique.