Surface longitudinal growth strain of plantation Eucalyptus urophylla×E.grandis

Surface longitudinal growth strain(SLGS) of plantation E.urophylla×E.grandis was measured by using strain gauge for evaluating the magnitude and variance of SLGS.Results show that SLGS is a kind of tensile strain and the mean value of SLGS of standing trees distributes between 650×10^-6 and 1 100×10^-6 mainly at 1.3 m height.Also,it needs about 3 min to measure SLGS normally since at this time,the strain releases completety and the value of SLGS turns to be stable.It is also found that there are no significant differences not only between two families of E.urophylla×E.grandis,but also two orientations(North and South) of stem and the relationship of SLGS with tree height is weak.