Study On Afforestation Density Effeacts On Growth And Wood Quality Of L.Sino-Americanum Clonal Plantation

In this paper, the effects of four kinds of afforestation density (666 N/hm2, 833 N/hm2,1111 N/hm2,1666 N/hm2) of 8-year-old Liriodendron sino-americanum(L.sino-americanum) plantation where studied. This plantation was located in north area of Guangxi. Through the effects of different afforestation density on growth, wood quality, and stem form traits, the scientific density would be put forward according to the cultivation objectives to maximize the operation benifit of L.sino-americanum afforestation. The main results are as follows:1、Afforestation density has a significant impact on the diameter at breast height (DBH), individual volume (Vi), and volume per hectare (Vh) of L.sino-americanum stand. Afforestation density had no significant effect on tree height (H) in the initial stage. But effects of afforestation density on H reached extremely significant level in the later stage. Stand began to close at four years old. At this point, the L.sino-americanum forest competition among individuals on water, fertilizer, sunlight, and space were more and more fierce. Afforestation density began to affect the growth of L.sino-americanum.2、At the age of eight, afforestation density was negatively correlated with DBH, H, and Vi. It means that the higher afforestation density came along with the smaller DBH, H, and Vi. Contrary, the lower afforestation density couple with the higher DBH, H, and Vi. The correlation level increased with age increasing.3、The quantitative maturity age (QMA) of different afforestation density were predicted. The QMA of 666 N/hm2,833 N/hm2,1111 N/hm2,1666 N/hm2 were 17a, 11a,10a, and 8a. At that time, the corresponding average Vi of four afforestation density were 0.32379 m3,0.23410 m3,0.18101 m3,0.11340 m3 respectively. When the four afforestation density achieved to the expected QMA, the expected Vh were 215.65 m3/hm2,195.00 m3/hm2,201.10 m3/hm2, 188.91 m3/hm2 respectively.4、Analysis of variance (ANOVA) showed that afforestation density have no significant effect on the wood basic density (BD) and wood fiber factors of L.sino-americanum. The correlation analysis showed that afforestation density have no correlation with the DB, fiber length (FL), fiber width (FW) and length/width (L/W).5、ANOVA showed that afforestation density have significant impact on DBH/height (D/H) and stem straightness, but have no significant effect on stem fullness and percent of bark. The correlation analysis showed that afforestation density positively correlated with stem straightness, but negatively correlated with D/H. And the correlations were all remarkable. It means that high-density may improve the stem straightness but reduce the stem taper of L. sino-americanum.6、The Topsis evaluation results showed that the preferred afforestation density to cultivate large diameter timber was 833 N/hm2, followed by 666 N/hm2,1111 N/hm2, and 1666 N/hm2. While preferred density for the middle diameter timber was 833 N/hm2, followed by 1111 N/hm2,1666 N/hm2, and 666 N/hm2. And the density of 1666 N/hm2 is suitable for small diameter timber production, followed by 1111 N/hm2,833 N/hm2, and 666 N/hm2.7、In the test area,833 N/hm2 was the reasonable density for L.sino-americanum plantation.