| Based on the information, the concept of microfibril angle, the relationship between microfibril angle and wood properties, the methodology for measuring microfibril angle, variation dynamics of microfibril angle, the factors affecting microfibril angle variation and future research prospects are discussed. In order to strength the competition capacity and oriental cultivation, more effort is devoted to the genetic improvement and cultivation of tree species, so as to make the timber production combining with demand of end products to wood properties in wood industry. Based on the review of related references, the temporal and spatial variation of microfibril angles and wood properties for 11 one-year-old poplar clones and 7 mature (more than 11 years old) poplar clones, the effects of planting densities, pruning intension and site conditions on microfibril angle and wood properties (wood densities, fiber length, fiber width and cellulose contents), and the relationship between microfibril angle and wood properties were studied in the paper, and the main conclusions are drawn as follows:1. There exists significant variation in microfibril angles and fiber length among 11 seedling poplar clones, microfibril angle varies from 13°to 30°and fiber length varies from 618.88um to 858.54um with the average 690.42um. Fiber width varies from 21um to 28um with the widest occurring in clone 35(P. deltoids CL'36/66') with 21 um, the least in siji (P. deltoidsx.P. nigra cv. Chile) with 21.3um. Significant differences have not been observed in cellulose contents in 11 one-year-old poplar clones and it varied from 41.4% to 47.4%.2. The results of variation analysis indicated that there were no significant differences in microfibril angles and fiber length within 6, 8 11 years old at breast height among 7 maturate poplar clones. The average of microfibril angle is 17.84° in 11 years old in 7 clones and it decreases 17.5% within 11 than in 6 years old. It can be ordered I-72> I-69> NL-351> NL-1388>NL-895>NL-447>NL-95 in averages of microfibril angles in 7 poplar clones within 11 years old. Significant differences were observed in wood density, fiber width and cellulose contents at breast height in 7 poplar clones. There exist notable difference between 1-72, NL-447, and NL-95 in wood density. It showed that the widest fiber occurred in 1-69 and NL-1388, the least fiber occurred in NL-95 and NL-895. There exist significant differences between NL-95, NL-895, NL-447 and NL-351, 1-69, 1-72, NL-1388 in cellulose contents.3. The spatial variation pattern of microfibril angle, wood density, fiber length, fiber width and cellulose contents are as follows:From pith to bark: The microfibril angle gradually increases from pith to 4-5 rings, after reach the largest in 4~5 rings, it start declining from pith to bark, and then it would be stable to a certain ring. Wood density was the least in the first ring and increased gradually from pith to bark. Fiber length, fiber width and cellulose contents were significantly increased from pith to bark.Within a single tree: Microfibril angle was lager at base of trees and decreased with the increase of height, and maintained stabilization over 6m height within trees. There existed an increasing trend in wood density from the base to tree top. The least occurred in the base, and the largest wood density occurred at 3.6m of the tree. Fiber length varies as "inverted saddle pattern" from base to tree top in one growth ring. The least fiber length occurred at base of trees and gradually increased with the increase of height, and fiber length reached the longest about 6m. The longest fiber would be stable to 17.6m, then it become declining. Fiber width was wider bellow 9.6m, it would be decreased beyond 9.6m in the tree.4. It proved from analysis of wood properties that there exist significant polynomial (R2=0.8263) and index (R2=0.8069) regression relationship between microfibril angle and growth rings; and polynomial... |
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