Abstract:

Wetwood is an abnormal phenomenon in growing trees, which adversely affects growth, subsequent wood processing and economic values of wood products. In this study, the influences of factors such as clones, afforestation methods, site conditions and climate conditions on the characteristics of poplar wetwood were studied through field investigations in 27 clones from 48 sample plots in 28 counties. Results showed that the incidences of wetwood were almost 100% in all plots. Ratios of wetwood area among the 48 plots differed from 15.1 to 90.2%. Wetwood area ratios, moisture contents and pH differed significantly between the 27 clones. Wetwood area ratios of the clones ranged from 18.7 to 62.3%. Ratios of wetwood areas were positively correlated with wetwood moisture content and pH, tree age, and negatively correlated with pH of sapwood. The repeatability of wetwood area ratios was 0.52, moderately controlled by genetics. Wetwood moisture content and pH were highly controlled by genetics, indicated by the repeatability of 0.91 and 0.89, respectively. There were significant differences in wetwood area ratios, moisture content and pH between different site conditions, afforestation methods, and geographical regions. Sloping land had the lowest wetwood area ratios and moisture content among four types of sites. Afforestation by direct seeding and rooted cuttings had the lowest wetwood area ratios and moisture content, respectively. In the three geographical regions, the Yellow River Basin had the lowest wetwood values of all three factors.

Key words: Poplar, Wetwood, Clones, Site conditions, Afforestation methods