Techniques of clonal selection, establishment of hedged stool-beds, and cutting propagation have been developed for Cunninghamia lanceolata
(Lamb.) Hook. (Chinese fir) in Zhejiang Province, China, and clonal forestry has been implemented in a local programme based at Kaihua County Forest Farm. Cutting propagation and the maintenance of juvenility, and plantation performance of 102 clones in single-row plots and multi-tree blocks, have been studied over different years and sites.
Hedged stool-beds with a density of 6.3 stools/m2 can provide 40-50 shoots per stool in the third year, when techniques for stimulating shoots have been used. Cuttings taken in the spring have an average rooting success of 90%, height at age 1 year of 35 cm, and basal diameter of 6 mm at a density of 52.5 plants/m2, at which point they are ready for transplanting to field sites.
Needle cuttings were developed to increase multiplication rates of superior clones. This involves cutting off needles (with a little xylem) from coppice shoots near the root collar, and setting during the period from January to March. Rooting was 85%, the height at age 8 years was 10 m, and diameter at breast height (dbh) was 12.4 cm, a similar performance to that of shoot cuttings. Stands developed from seedlings of elite families and cuttings of the third propagation cycle had a similar growth rate. The performance of successive propagations of cuttings showed no significant decline in rooting and growth over 11 propagation cycles. Hedged stool-beds can prevent trees from ageing and keep shoots at a juvenile stage.
If the test materials are classified into four levels of improvement—"elite clones", "average of best 23 clones", "elite families", and "first-generation seed orchard offspring"—gains in single-tree-volume (STV) at age 9 years were respectively 67%, 24%, and 15% over the seed orchard offspring. Of all selection materials, the best were crosses between selected parents from different provenances. The first screening of clones was carried out at 4-5 years after planting, the second at 6-7 years, and the final screening at 8-12 years (9.5—11.5 m height). Selection of 15 clones out of 102 resulted in a gain of 86% in STV over the Napo, Guangxi, check. Planting single-clone blocks of a genetically-diverse range of clones can increase yields per unit area. Up to the present, 2700 ha have been planted on Kaihua Forest Farm and increases in yield of over 50% are expected.