Linking root xylem anatomy to tensile strength: insights from four broadleaved tree species in the Hyrcanian forests

Aims

High root tensile strength (RTS) is crucial for tree stability, windthrow resistance, soil reinforcement, and erosion control. However, RTS varies across species, and the underlying causes remain poorly understood. RTS is directly linked to anatomical structure and fiber morphology, which influence its resistance to stress. This study explores the relationship between xylem anatomy and RTS in four broadleaved species—Acer velutinum, Fagus orientalis, Quercus castaneifolia, and Carpinus betulus—from the Hyrcanian forests of Iran.

Methods

RTS was measured, and fiber biometry, including fiber length, width, lumen width, and wall thickness, was quantified on macerated fibers. Vessel lumen fraction was also assessed through microscopic examination of root cross-sections.

Results

A. velutinum (Persian maple) exhibited the highest RTS, while F. orientalis displayed the lowest. A negative power relationship was observed between root diameter and RTS. Among fiber traits, fiber length and width had the strongest positive influence on RTS. Persian maple, as the species with strongest root, possessed the longest and widest fibers. Conversely, F. orientalis, the weakest one, displayed the shortest and thinnest fibers with the most robust cell walls. The relationship between quantitative vascular features of xylem and RTS was inconclusive, across species.

Conclusion

This study revealed the complex interplay between xylem anatomical traits and RTS. Fiber characteristics, particularly a dense network of long, wide, and more flexible fibers, were found to strengthen root. Further research should explore the interplay of multiple anatomical features to provide a comprehensive understanding of RTS.