| With shortage of timber resources, oriented cultivation is one of an important measure to solve the shortage of timber; forest management measures have a major impact on the timber production and quantity. Oriented cultivation in short cycle has already become a focus of forestry research. In this study, the growth conditions, anatomical characteristics, wood density and chemical composition changes of four initial planting density (4444/hm2,3333/hm2,2500/hm2,1666/hm2)in Jingzhou 14-year-old Hongqi pulpwood forest were studied, which provided scientific basis for decision making for the slash pine oriented plantation and utilization. The results showed that:Planting densities of slash pine significantly affected the average diameter at breast height. Analysis of variance showed that the average DBH of four densities were significantly different. Planting densities of slash pine had no obvious effect on average height. High density may in certain degree promote high stand growth. Meanwhile, the high-density on the promotion of the tree height was limited because of competition within the space and nutrition. Analysis variance of average tree height showed that differences of the four planting densities were not remarkable. The densities of slash pine had obvious influence on average individual volume. The variance analysis indicated that the average single timber volume difference was extremely remarkable. The maximum individual volume achieved 0.06m3 in density of 1666/hm2.Along with lower density, the space for per tree increased, so its root system developed. Four kinds of different densities root system by 4.0 diameter levels were at 3333/hm2,2500/hm2 and 1666 /hm2, while by 2.0cm at 4444/hm2 primarily. Trees’nutrition absorption was closely related to the root system of medium diameter level. The density of stocking was smaller; the ability of absorption of stand was higher, because of more root system with 4.0 diameter level.Slash pine planting densities had obvious influence on annual ring width. The annual ring width increased rapidly from the pith to the bark,5-6a reaches to the peak, then reduced gradually, assuming the stable tendency after 12a. As the densities increased, ring width showed a downward trend.The variance analysis indicated that the percentage of latewood difference was not remarkable among four densities. The radial variation of the latewood percentage had the tendency of increasing gradually. The peaks of latewood percentage all appeared in 14a.The four kinds average percentage of latewood was 35.63%,35.11%,37.39% and 32.03%, The density 2500/hm2 had biggest percentage at 37.39%, was higher than other densities, the smallest was 1666/hm2 at 32.03%.The radial variation of basic density of slash pine changes tendency belonged to the first situation of Panshin, increasing gradually. Four densities peaks achieved in 12a, It was advantageous with density of 0.4-0.6g/cm3 to the wood-pulp production. In four densities, the highest basic density of wood was the planting density by 2500/hm2 at 0.3875 g/cm3.The next was the density 4444/hm2 at 0.3861 g/cm3, while the smallest was the density 1666/hm2 at 0.3544g/cm3. The basic density of four planting densities was more than 0.4 g/cm3 in 9a-10a, and all tends to stably, the variance analysis indicated the planting density of the difference was not remarkable.The variance analysis indicated that the difference of the tracheid length was remarkable in four densities of planting. The tracheid length of four planting densities was between 2674μm-3260μm, belonging to the long textile fiber of raw material, can accord with the pulpwood requirement. The tracheid length was long by density of planting 2500/hm2 and 4444/hm2. Difference of different planting densities of tracheid width was not significant, with the planting density increased, while the tracheid width decreased. The average tracheid width was in 35.13μm-37.76μm. Four planting densities of ratio of fiber length to width was between 73.87-95.78, was quite higher than 35, and was fine raw material for pulpwood. The analysis indicated that the variance of ratio of fiber length to width was more remarkable than the difference of four planting densities. Longer tracheid length and breadth were by density of 2500/hm2 and 4444/hm2. The average wall thicknesses of four planting densities were between 0.35-0.44, particularly suitable for paper-making. Average double-wall thickness of four planting density was between 7.86μm-10.32μm. Double-wall thickness by planting density in 1666/hm2 was more than 10μm, while the average thickness of the other three densities was generally 8μm. Ratio of lumen to diameter was called flexible factor. Its value was close to 1, the paper pulling force was stronger. Ratio of lumen to diameter of four densities between 0.71 and 0.77 were close to 1.By density of 2500/hm2 and density of 3333/hm2 of average close to general request of 0.75-1, meets the paper requirements. The microfibril angle of four planting densities was between 22.50°-23.55°, the coefficient of variation was between 10.7%-17.2%, with the density increasing, microfibril angle tended to decrease. With higher density, the microfibril angle tended to increase. In density 1666/hm2 and 4444/hm2, the microfibril angle was quite large. While in the medium-density 2500/hm2 and 3333/hm2, the microfibril angle was smaller.Four planting densities cellulose content were between 46.08%-49.05%, the maximum density content was 3333/hm2, while the minimum was 1666/hm2, and the coefficient of variation approximately 6%. The lignin was removed in the pulpwood system. Four densities of planting lignin content were between 26.68%-27.56%, the density by 3333/hm2 was low, but four disparities were not obvious. Lower extracts content was advantageous to the system of pulpwood. Hot water extractive content of four densities of planting was between 5.38%-6.17%, conforming to the pulpwood requirement. The alcohol benzene extractive content was between 2.74%-2.94%. Hot water extractive content and the alcohol benzene extractive content were somewhat high at density 4444/hm2, but the overall content was somewhat low, was advantageous to the pulpwood system.Planting density of 1666/hm2 and 2500/hm2 can yield larger sum of pulp paper. Considering the various factors and indicators, the initial planting density 1666/hm2 was suited to be cultivated for large diameter timber and the density 2500/hm2 was ideal planting density for slash pine pulpwood. |
