Do root modules still exist after they die?

Abstract

Background The terminal branch orders of plant root systems are increasingly known as an ephemeral module. This concept is crucial to recognize belowground processes. However, it is unknown if root modules still exist after they die? Methods The decomposition patterns of the first five root orders were observed for 3 years using a branch-order classification, a litter-bag method and sequential sampling in a common subalpine tree species (Picea asperata) of southwestern China. Results Two root modules were observed during the 3-year incubation. Among the first five branch orders, the first three order roots exhibited temporal patterns of mass loss, nutrients and stoichiometry distinct from their woody mother roots throughout the experimental period. This study, for the first time, reported the decomposition pattern of each individual root order and found a similar decomposition dynamic among ephemeral root branches in a forest tree species. Conclusions Results from this study suggest that root modules may also exist after death, while more data are needed for confirmation. The findings may further advance our understanding of architecture-associated functional heterogeneity in the fine-root system and also improve our ability to predict belowground processes.