Quantifying Characteristics of Fine Roots Contributing to Water Flow Process in Rocky Mountainous Area Using Dye Tracer Experiment and Monolith Method

Abstract

Root channel serve as one major type of pathway for water flow in forest soil. In this paper, we combined a dye tracer experiment and a monolith method to distinguish the fine roots (0 < d ≤ 5 mm) that served as preferential water flow pathways in rocky mountainous areas. The characteristics of these types of roots among different soil layer and different root diameter were discussed. In this modified method, two typical forest species in Mount JiuFeng were selected. One was broad-leaved forest (BF) with Quercus variabilis, and the other one was needle-leaved forest (NF) afforested with Platycladus orientalis (L.) Franco. Monoliths were taken from horizontal profiles along with the soil depth after the dye tracer experiment was conducted. Fine roots contributing to water flow processes were defined as being dyed by the colour of the tracer and selected from the soil. Our results showed that not all of the fine roots can contribute to water flow, even in the soil layer of 0 to 10 cm. In the soil layer of 0 to 30 cm, the proportion of fine roots with 0 < d ≤ 1 mm made more than approximately 50% contributions to water flow in every soil layer. Meanwhile, the share of stained fine roots with a diameter of 1 < d ≤ 5 mm had an increased trend along soil depth, which was more clear in NF than in BF