Abstract:

Effects of Larix kaempferi pruned in different types on growth and cutting production of ortets,cutting rooting ability and growth of 2-year-old rooted cuttings were compared at different ages (from 2-year-old to 10-year-old) of ortets. The result showed that ortets originated from L. kaempferi seedlings were cut at a height of 20～140 cm and trimmed or pruned each year could delay the time of occurrence of aging effect and reduce the effect to some extent. Rooting percentage of cuttings taken from 10-year-old ortets pruned in different types,which was 55.2%～81.1%,were extremely higher than that of cuttings taken from ortets of tree form in the same age,which was 24.8%.This showed that pruning each year could rejuvenate the tissue of ortets when they got older. Ortets pruned in different types resulted in different growth (diameter above ground), cutting production and rooting percentage of cuttings collected from them. Ortets pruned in long- and middle-sized cylindricality grew better, and produced more cuttings because of they were pruned relatively light compared with low-sized table type. These two types of ortets produced 110.5, 237.0, 173.0 cuttings and 85.9, 150.7, 98.0 cuttings respectively on average at ages of 3.5, 5.5, 8.5 years old, which were obviously higher than ortets pruned in low-sized table type with 54.3, 61.4, 43.0 cuttings. Though the long- and middle-sized cylindricality ortets had advantages in growth and cutting production, the effects of controlling maturation and rejuvenating were not as well as expected. Rooting percentages of cuttings taken from ortets of long- and middle-sized types decreased after ortets were 5.5-year-old, then sharply down to 58.3% and 55.3% respectively. Ortets of low-sized table type had lower survival and growth rate, and lower cutting production owing to heavy pruning,but gave good results in delaying aging effect and rejuvenating. Rooting percentage of cuttings collected from low-sized table ortets decreased smoothly after ortets were 7.5 years old, which was two year delay compared with long-sized cylindricality. Rooting percentage of cutting could still be 81.1% when the ortets were 9.5 years old. There was no obvious difference in height growth of two-year-old rooted cuttings derived from different types of ortets when they were younger (2.5-year-old), yet significant difference in height growth could be found between two types of 2-year-old rooted cuttings derived from ortets of low-sized table and long-sized cylindricality type when they were 7.5 years old. For increasing cutting production, ortets should be pruned in long-sized cylindricality type at the primary stage when the orchard was just established,and after years (8 years old) the ortets should be cut back (from the height of 40 cm above ground) to improve rooting ability of cuttings and prolong using time of the orchard.

Key words: Larix kaempferi, Pruning of the ortets, Rejuvenation, Rooting percentage, Growth of rooted cuttings