High-efficient management technology of big-diameter timber of Cunninghamia laceolata

ObjectiveThe cultivation technology of Chinese fir big-diameter timber was studied to promote scien-tific management of big-diameter timber plantation . MethodThe big-diameter timber demonstration plantations at Shankou Forest Farm in Nandan County were investigated to analyze the effects of different germplasm sources, site conditions and reserve densities on big-diameter timber cultivation. ResultThe mean annual growth,growth and big-diameter timber ratio of Chinese fir from improved variety stands were extremely significant or significant higher than those of common species stands used as control (P<0.05 or P<0.01, the same below). As for 21 years old Chinese fir, the big-diameter timber quantity ratio and its per unit area volume of the plantations were improved by 5.4 times and 7.4 times respectively than that of the control. The growth of Chinese fir big-diameter timber stands was significantly affected by the site indexes. The reserve density had different effects on the growth of stands with different site indexes. Under the site condition with site index above 20 ( including 20 ) , it was good for cultivating Chinese fir big-diameter timber with the best reserve density of 800-900 plants per hectare. Under the site condition with site index of 18 ,it was good for cultivating Chinese fir big-diameter timber or middle-diameter timber with the best reserve density of 800-1100 plants per hectare. Under the site condition with site index of 16,it was good for cultivating Chinese fir mid-dle-diameter timber with the best reserve density of 800-1200 plants per hectare . ConclusionUsing improved vari-ety and under the site condition with site index above 20 (including 20),it is good for cultivating big-diameter timber of Chinese fir with the best reserve density of 800-900 plants per hectare.