Fine root dynamics in organic and mineral soil layers of <Emphasis Type="Italic">Cryptomeria japonica</Emphasis> D. Don plantation

Fine root dynamics and root architecture were studied in the organic and mineral soil layers of a Cryptomeria japonica plantation. Fine root biomass (<1 mm) showed seasonal changes whereas fine root biomass (1–2 mm) was unchanged over the study period. Root tips were grouped into size classes based on root tip diameter, including <0.5, 0.5–1, and 1–2 mm. Root tip density (<1 mm) was significantly correlated with fine root biomass (<1 mm). Root tip density and fine root biomass (<1 mm) increased in summer and decreased in winter, and both showed a similar seasonal pattern. Root tip dynamics influenced fine root dynamics. Root architecture as expressed by branching intensity changed with root tip production and mortality. Branching intensity also showed a similar seasonal pattern of root tip density dynamics. Root tips of both <0.5 and 0.5–1 mm were mainly produced in the organic soil layer, while root tips of 0.5–1 mm were mainly produced in the mineral soil layer. Because of the high RT1 root tip production in the organic soil layer, branching intensity was higher in the organic soil than in the mineral soil layer during summer. Root tip dynamics influenced fine root dynamics and the architecture of root systems in both organic and mineral soil layers.