The arbor root of Betula platy phylla was investigated in North China and the mechanical characteristics of arbor root system were quantitatively researched based on analysis of variance by using the result of root tensile test as basic data.According to the experiment al design criteria

three indexes

including rate

root length and diameter

were selected as influence factors ref lecting birch root mechanical characteristics.Four indexes

including root tensile resistance

root tensile strengt h

elastic modulus and limit extensile rate

were selected as responding factors.The results showed t hat root diameter had significant effects on root tensile resistance

root tensile strength and limit extensile rate

both root length and t ensile rate had significant effect s on elastic modulus and limit ext ensile rate.As the four responsive indexes were concerned

there w as no interact ion between rate of extensile and root length.As for tensile strength and tensile resistance

the interaction between rate of extensile and root diameter

as well as root length and root diameter both existed and had significant expressions at different levels.As elastic modulus and limit ext ensile rat e were concerned

the interaction between root length and root diameter was not significant

while the interact ion between rate of ext ensile and root diameter was significant.