Comparative Study on Growth Characteristics of Walnut Hybrid ‘Zhongningqi’, Juglans hindsii and Juglans major

Objective The aims of this study are to understand the tree growth process of walnut hybrid ‘Zhongningqi’(Juglans hindsii×Juglans regia var. Zhongningqi), and provide reference for its variety application and high quality wood production through comparative studies on the tree-ring growth characteristics of “Zhongningqi”, Juglans hindsii and Juglans major. Method By stem analytical method, the growth of DBH, tree height, volume and growth process of ‘Zhongningqi’, Juglans hindsii and Juglans major planted in Luoning County of He'nan Province were analyzed. Result In the growth process, with the increase of age, the growth rates of DBH, tree height and volume of the three species showed a tendency of decrease and the growth rates were basically stable after the 14 years-old. The breast height form are 0.37-0.42, so the trunk of the three species are straight. The fast growing period of DBH of ‘Zhongningqi’ and J. hindsii is the 2nd to the 8th year, and that of J. major is the 2nd to the 10th year. The total DBH increment and average annual increment of ‘Zhongningqi’ are the highest, which are 36.68 cm and 1.59 cm respectively. The fast-growing period of the tree height could last for 8 years. The total growth of timber volume increment and average annual increment are keeping until the 23rd year, but the peak value of annual increment of timber volume does not reach the quantitative maturity then. The total timber volume increment and average annual increment of ‘Zhongningqi’ are the highest, with 0.49 m3 and 0.02 m3 respectively. Conclusion As the rootstock, ‘Zhongningqi’ can be used for fast-growing and high-quality timber species and it is a good choice for cultivating big diameter wood. Meanwhile, ‘Zhongningqi’ will play an important role for cultivating high-grade furniture material.