Mycorrhizal associations and root morphology shape mechanical performance in woody plants from cold regions

Root mechanical traits, including load for failure in tension (F_r), tensile strength (T_r), tensile strain (ε_r), modulus of elasticity (E_r), and tensile toughness (W_r), are critical for plant anchorage and soil stability. These traits are shaped by root morphology, type (absorptive and transport roots), and mycorrhizal associations (arbuscular mycorrhizal and ectomycorrhizal fungi). This study investigates the relationships among these traits. We examined mechanical traits across eight woody species with different mycorrhizal associations, categorizing roots into absorptive and transport types. Root morphological traits - root diameter (RD), specific root length (SRL), root tissue density (RTD), and root biomass (RB) - were measured. Tensile tests were conducted to assess mechanical properties. Statistical analyses, including regression and principal component analysis (PCA), were used to elucidate trait relationships. Transport roots exhibited superior mechanical properties compared to absorptive roots, with RD and RB showing significant positive correlations with mechanical traits. AM roots demonstrated higher tensile strength, strain, and toughness than EM roots. PCA highlighted RD and SRL as dominant factors influencing root mechanical performance, while RB contributed significantly to transport roots' structural stability. This study underscores the critical role of root morphological traits and mycorrhizal associations in determining mechanical performance. These findings highlight the ecological trade-offs between mechanical stability and resource acquisition, offering novel insights into root functional strategies and their implications for ecosystem stability.