Fine root turnover in sugar maple estimated by 13C isotope labeling

We evaluated variation in root turnover across five root orders in sugar maple (Acer saccharum Marsh.) saplings growing in a northern hardwood forest in central New York, USA. We used a stable isotope approach in which root systems were labeled with C-13 and root structural C sequentially sampled for C-13 enrichment. Turnover of first- and second-order roots was apparently rapid with only about 5% of the C-13 retained in living roots after two growing seasons. Although third-to fifth-order roots appeared to persist longer, differences among root orders were not statistically significant, probably mostly because of highly nonuniform initial labeling. This nonuniform labeling constrains the precision of root turnover quantification using this approach.