关键词: 细根, 根系分支, 导管, 分布, 导水率

Abstract: Aims Juglans mandshurica Maxim., Fraxinus mandshurica Rupr. and Phellodendron amurense Rupr., are widely used timber hard woody species in Northeast China, having contrasting root architectures. Exploring the distributions of vessels with different sizes and their contribution to the theoretical cumulative and specific hy-draulic conductivities would be important for the understanding of the trade-off between transport efficiency and safety, as well as the tree species selection in the afforestation practice. Methods In this study, we sampled the fine root branches of J. mandshurica, F. mandshurica. and P. amurense, measured the anatomical and morphological traits of the first five order roots Important findings Our results showed that root vascular traits varied widely. Specifically, with the increasing root order, the mean, maximum and mean hydraulic diameter of vessels, the number of vessels, and both the theoretical cumulative and specific hydraulic conductivities increased across three examined woody species. However, the vessel density showed less variation across root orders. Generally, P. amurense had a sparse branching root system, all three diameters of vessels were higher than those of J. mandshurica and F. mands-hurica with dense root branches, which were also similar to the theoretical cumulative and specific hydraulic conductivities. Among the three selected species, the small vessels occupied the largest proportion in the root cross-section, but the fewer and wider vessels made a great contribution to the theoretical cumulative and specific hydraulic conductivity. Additionally, vessels with a diameter more than 30 m have a high risk of embolism. In this study, vessels with more than 30 m were only found in fifth order roots, their proportions were 0.35%, 0.54% and 2.16% in J. mandshurica, F. mandshurica and P. amurense, respectively, which indicated that the risk of root xylem embolism under freeze-thawing in spring or drought in summer would be higher in P. amurense than in J. mandshurica and F. mandshurica. Our results revealed the inter- and intra-specific variations of fine root vascular traits and the functional trade-off between transport efficiency and safety, which would deepen our understanding of the root hydraulic strategies, as well as the specific selections of tree species or planting sites.

Key words: fine root, root branch, vessel, distribution, hydraulic conductivity