Integrated Selection of Populus nigra Clones by Growth and Wood Quality Properties

The genetic variation in wood property among 14 clones of Populus nigra was studied by means of measuring the Pilodyn index of the standing living trees in the nondestructive way. The correlations among the Pilodyn index value and the density indexes of the timber were statistically analyzed by measuring the DBH value and the Pilodyn penetration on the south aspect of the living P. nigra trees (Ps) in the plantation, and by determining the basic density of the core wood (Ds), the density of outer wood (Dso) in the lab. Based on the mean values of Ps, Dso and Ds indexes of each clone tested, there were extremely significant correlations (-0.8329-0.9648) among the three index serials, There were extremely significant correlations among the Ps, Dso and Ds index values of the individual P. nigra living trees (-0.8252-0.9184), and there were also extremely significant correlations among the means of Ps, Dso and Ds index values of the 14 P. nigra clones (-0.8876-0.9743) respectively. The results of the ANOVA analysis on the values of Ps, Dso and Ds indexes also showed there was remarkable difference in the wood properties among the P. nigra clones. The 14 clones were classified into 4 groups based on the three indexes integrated with the DBH average, i.e., the high wood density with fast growth rate group; the low wood density with fast growth rate group; the high wood density with slow growth rate group; and the low wood density with slow growth rate group. The outcome of ANOVA analysis and Multiple Comparison analysis proved that there were significant differences among the 4 groups. 5 clones characterized with fast growing and high wood density, i.e., No. 8000, ‘Jiangyang’, No.95, No.153 and No.172 were finally selected by the clustering analysis results.