| Based on the preliminary selection of 104 Populus deltoides clones,we selected the 14clones of P.deltoides and 3 widely planted clones(I-69,Nanlin-95 and Nanlin-895)as control groups to investigate their growth traits and wood properties.In this study,growth traits,wood mechanical property,wood chemistry constituents and wood fiber traits of 17 clones were determined and compared,while the temporal and spatial variation of chemistry constituents and fiber traits were explored.Furthermore,based on growth traits and wood properties,a comprehensive evaluation for tested poplar clones was made in order to select superior poplar clones for industrial plantations.The results from this study provide a theoretical foundation for the P.deltoides plantation establishing and directive breeding in lower-and-middle section of Yangtze river.The main conclusions were as follows:(1)The variation range of DBH among selected clones was 36.5cm～52cm at age 25,and the best clone was S3239.The variation range of tree height among selected clones was30.6m～33.7cm,and clone S366 achieved highest growth.The variation range of tree volume among selected clones was 1.42m~3～2.97m~3,and the best clone was S3239.(2)There were significant differences in wood bending strength,bend elastic modulus and compression strength parallel to grain among the 17 clones.The variation range of wood bending strength among selected clones was 39.26MPa～64.42MPa,and the best clone was S3239.The variation range of wood bend elastic modulus among selected clones was 4619MPa～7773MPa,and the best clone was S3239.The variation range of wood compression strength parallel to grain among selected clones was 31.21MPa～42.78MPa,and the best clone was S3238.Wood bending strength,bend elastic modulus and compression strength parallel to grain had an extremely significant positive correlation in each other(3)Based on comprehensive strength value,S3238 was the best clone among 14 selected clones,achieving 106.55MPa,whereas S3412 was the best clone among selected clones based on physical factor,hitting to 2856×10~5Pa.Clones S371、NL-95、I-69 and S313 belong to low-intensity and low-middle-quality wood,while the other clones are low-intensity and high-quality wood.(4)There was a significant difference in average wood extraction content among the 17clones.The variation range among selected clones was 0.81%～0.58%,and the lowest content was observed in clone S3200.With the increase of tree age(from pith to outmost),the average wood extraction content showed the increasing tendency.(5)There was a significant difference in average wood cellulose content among the 17clones.The variation range among the selected clones was 52.6%～45.8%,and the greatest content was detected in clone S3312.With the increase of tree age(from pith to outmost),the average wood extraction content showed increasing tendency,but only a small fluctuation was observed after 14 years..(6)There was a significant difference in average wood hemicellulose content among the17 clones.The variation range among the selected clones was 20.8%～16.7%,and the highest content was observed in clone S3240.With the increase of tree age(from pith to outmost),the average wood hemicellulose content showed the reducing tendency.(7)There was a significant difference in average wood lignin content among the 17 clones.The variation range among 14 selected clones was 26.76%～23.23%,and the lowest content was detected in clone S371.With the increase of tree age(from pith to outmost),the average wood lignin content showed the reducing tendency.(8)There was no significant difference in average wood fiber length among the 17 clones.The variation range among the selected clones was 1265μm～1148μm,and the best clone was S3240.The average wood fiber length radially increased in different tree age,but only a small fluctuation was observed after 17～20 years.With the increase of tree height(from lower to top),the average wood fiber length showed the reducing tendency.There was no significant difference was found in wood fiber length between male and female plants.(9)There was a significant difference in average wood fiber width among the 17 clones.The variation range among the selected clones was 25.21μm～23.64μm,and the best clone was S31.The average wood fiber width radially increased in different tree age,but only a small fluctuation was detected after 17～20 years.With the increase of tree height(from lower to top),the average wood fiber width showed the reducing tendency.There was no significant difference was found in wood fiber width between male and female plants.(10)There was a significant difference in the ratio of fiber length to width among the 17clones.The variation range among the selected clones was 50.91%～46.46%,and the best clone was S3240.The average ratio of fiber length to width radially increased in different tree age,but only a small fluctuation was detected after 17～20 years.With the increase of tree height(from lower to top),the average ratio of fiber length to width showed the reducing tendency.There was no significant difference was found in ratio of fiber length to width between male and female plants. |
