Research On The Relationship Between Growth Strain And Wood Properties Of Poplar Tension Wood

Plantation poplar has been widely planted in China because of its fast growth rate and wide utilization and has become an important industrial timber species in China.In order to investigate the mechanism of plantation poplar growth stress formation and to improve the utilization value of plantation poplar,in this study,The surface axial growth strain of nine poplar trees（Populus euramericana cv."Zhonglin46"）live standing trees were measured,and the relationship between microscopic anatomical properties,physical and mechanical properties,cell wall microscopic characteristics and growth strain of poplar trees in plantation forests were analyzed.The main findings of this thesis,were as follows:（1）The growth strain measured on the surface of poplar tension wood was different along with circumferential positions,The average is in the range from242.28μεto479.10με,the highest value of growth strain was located at the upper side of the inclined trunk,the minimum value appeared at the lower side of the inclined trunk,and the growth strain values of other positions were between these two positions,and the ANOVA results showed that the difference of growth strain on the surface of poplar trees in different plants and positions was highly significant,and there was no significant difference of growth strain between different heights.（2）The anatomical characteristics of the specimens changed at different circumferential positions of poplar tension wood plants,all fiber cells in the tension zone contained gelatinous layer,some fiber cells in the lateral zone contained gelatinous layer,few gelatinous fiber cells existed in the opposite zone,wood fiber length,fiber width,fiber length to width ratio,double wall thickness,vessel diameter,and proportion of vessel showed radial variation patterns increasing with the growth of tree annual rings,proportion of fiber decreased with the growth of tree annual rings,and proportion of ray showed a non-distinct trend.The fiber length ranged from 1160μm to 1400μm,the fiber length to width ratio from ranged 48.17 to 73.64。The fiber length to width ratio at a high level.There were significant positive correlations between fiber length,fiber width,proportion of vessel,double wall thickness,vessel diameter,proportion of fiber with growth strain value,and significant negative correlations between vessel diameter,proportion of vessel with growth strain value,and non-significant correlations between proportion of ray and growth strain.（3）The physical and mechanical properties of the specimens changed at different circumferential positions of poplar tension wood plants.The basic density,bending strength,bending modulus of elasticity,and compressive strength of the wood showed a radial variation pattern that increased with the growth of the annual rings of the trees,and the microfibril angle showed a radial variation pattern that decreased with the growth of the annual rings of the trees.There were significant positive correlations between basic density,bending strength,bending modulus of elasticity,compressive strength with growth strain,and significant negative correlations between the microfibril angle with growth strain.（4）When using AFM PF-QNM mode to test the elasticity modulus of poplar cell walls at different growth strain locations,the results showed that for the same plant the average elastic modulus of different wall layers was the highest in the high growth stress zone compared to other locations,the average elastic modulus of each wall layer of the cell wall without gelatinous layers was significantly lower than the other regions.In addition,the elastic modulus of different wall layers in wood fiber cells was compared,where the elastic modulus of the gelatinous layer was the largest in fiber cells containing the gelatinous layer,which was slightly larger than that of S₂layer,and the smallest in S₁layer,and the elastic modulus of S₂layer was larger than that of S₁layer in fiber cells without gelatinous layer.