In order to investigate the influences of root diameter,root length and tensile rate on stress-strain curve,four common arbor root systems,i.e.,Pinus tabulaeformis,Betula platyphylla,Quercus mongolica and Larix gmelinii,were selected to perform tensile experiments.Results show that the overall stress-strain curve of every single arbor root system is the single-peak curve and does not have the apparent sizeshrink phenomenon.Stress-strain curves for the four trees present elastoplastic material characteristics. Under the same loading condition and with the same diameter size,Betula platyphylla performs the tensile mechanical properties close to Quercus mongolica,both of which have larger elastic modulus and tensile strength and smaller elongation;Pinus tabulaeformis and Larix gmelinii have similar mechanical properties,with smaller elastic modulus and tensile strength and larger elongation.With the increase in root length,elastic modulus of Larix gmelinii manifests a downward trend,whereas elastic moduli of the other three trees manifest an increasing trend.Both of the ultimate elongation and tensile strength are negatively correlated with the root length.For Betula platyphylla and Larix gmelinii,the increase in tensile rate makes roots to be failure more easily;elastic modulus and tensile strength are negatively correlated with tensile rate;and ultimate elongation is positively correlated with and the tensile rate.