Estimation of fine-roots turnover. Towards a revision of global carbon balance?

A comment is made on a recent paper published on Science (Strand et al. 2008), in which authors demonstrate an irreconcilable difference in fine-root life spans estimation with two different methodological strategies. In this paper authors point out on major discrepancies and errors from carbon isotopes based analysis and direct observations based on minirhizotron methods. In both cases a revision of fine-roots contribution to the global carbon cycle is required.