Item

Abstract

We used bomb-radiocarbon and raw minirhizotron lifetimes of fine-roots (<0.5 mm in diameter) in the organic layer of Norway spruce forests in southern Sweden to test if different models are able to reconcile the apparently contradicting turnover time estimates from both techniques.

• We present a framework based on survival functions that is able to jointly model bomb-radiocarbon and minirhizotron data. At the same time we integrate prior knowledge about biases of both techniques – the classification of dead roots in minirhizotrons and the use of carbon reserves to grow new roots.

• We found that two-pool models, either in parallel or in serial setting, were able to reconcile the bomb-radiocarbon and minirhizotron data. These models yielded a mean residence time of 3.80 ± 0.16 years (mean ± SD). On average 60 ± 2 % of fine-roots turned over within 0.75 ± 0.10 years, while the rest was turning over within 8.4 ± 0.2 years.

• Bomb-radiocarbon and minirhizotron data alone give a biased estimate of fine-root turnover. Both datasets are reconcilable. The two-pool models allow a mechanistic interpretation for the coexistence of fast and slowly cycling roots – branching and suberization for the serial-two-pool and ectomycorrhizal fungi-plant interactions for the parallel-two-pool model.