Variation And Utilization Evaluation Of Wood Properties In Growth Process For Loblolly Pine Pulp Forest In Anhui Province Of China

Loblolly pine was one of the most important short-cycle timber species which was introduced sucessfuly and planted in southern of china.It had great relation with cultivation environment in growth properties,wood quality.The variation in wood properties of loblolly pine had great difference in different environment.Loblolly pine plantation of 19 year old were choosed to study in this paper,the objectives of this paper were to deal with the wood properties variation and utilization evaluation,which provide scientific basis and theoretical foundation for oriented cultivation and wood utilization of loblolly pine.The loblolly pine plantation of 19 years old,its fast growing period of tree height was 1-5a.The average annual increment was 0.9947m.The maximum value of the current annual increment was 1.34m.The mean annual increment of DBH reached the maximum value 1.53cm at 6a.Its value range was from 0.25cm to 2.307cm.The maximum value of the current annual increment was at the 13^th year,the mean annual increment increased straight line after the 4th.The annual ring width increased rapidly at 1-5a in radial direction,the 5^th year reached the max value and and then decerased sharply.The annual ring width levelled off after 12a.Polynomial regression equation of annual ring width and the tree age was significant differences at the 0.01 level.The latewood percentage increased rapidly at 1-3a in radial direction,increased steadily at 4-10a,leveled off after 11a.Regression equation of latewood percentage and the tree age was significant differences at the 0.01 level.In the radial direction,tracheid length(TL) increased gradually from pith to park, it increased rapidly at 1-8a and leveled off after the 12a,the average of early wood was 2516μm and latewood was 2777μm.Quadratic function and by square were the best choice to describe variation of TL with annual ring increasing;the radial variation mode of tracheid width(TW)and tracheid diameter(TD) was basically similar,they all increased from pith to park and then levelled off;the variation of tracheid double wall thickness(TDWT) levelled off at 13 annual ring;tracheid length-width ratio(TLWR) increased from 1a to 9a,it increased slowly at 9-12a, levelled off after 13a;tracheid double wall thickness-diameter ratio decreased from pith to park,maintained stable after 9a,the range of variation coefficient was 2.20%-21.99%;tracheid diameter-width ratio firstly increased slightly and finally leveled off,the change tendency was not great.In the axial direction,TL increased upward from the base,it reached the max at 3.3m which was 2925μm.The variation pattern of TL at the axial was "short-long-short" tendency;the variation of TW and TD in axial direction were both not very big;the axial variation of tracheid double wall thickness(TDWT) showed drop tendency,the variation range was 9.67μm-10.97um,the mean value was 10.66μm.The axial variation of TLWR was similar to TL,the mean value was 64.40,the range of variation value was 47.01-74.20;tracheid double wall thickness-diameter ratio in axial showed big-small-big tendency,the range of the value was 0.33-0.40,the variation coefficient was 7.65%-18.70%;tracheid diameter-width ratio increased in axial direction,maximized at 5.3m which was 0.76 and then decreased,the average value was 0.75.The mean value of basic density of loblolly pine was 0.383 g/cm³.In the radial direction,basic density increased from pith to the park,maintained stable at 13a,the radial variation pattern were PashinI type,namely it inceased gradually from pith to park, finally maintained stable after some year.In axial direction basic density showed decline trend,the difference was not significant among differen tree heights.The content of extractives of loplolly pine decreased at the radial direction,reaching the max at the pith which was 14.8%.The content of extractives showed increment trend at axial direction, the maximun value was near park which was 10.21%,the difference of the content of extractives was not significant among differen tree heights.The radial variation of microfibrillar angle of earlywood was similar to that of latewood.They all dicreased at radial direction.The variation range of earlywood was 17.80°-21.12°and that of earlywood was 15.94°-20.45°.The value of earlywood was obviously larger than that of latewood at the same annual ring.Trinomial regression equation reached 0.05 remarkable level between microfibrillar angle and annual ring.At axial direction,microfibrillar angle maximized 19.84°at 0.3m and then decreased gradually,the range of value was 14.53°-19.84°.The variation coefficient of tracheid length,length-width ratio,the content of extractives was larger within trees than that of other wood properties index,tracheid length,length-width ratio,basic density etc the majority wood characteristic among trees was lower than that of within trees.There was mostly negative correlation between basic density and annual ring width at 1a-8a.Basic density was positive correlation with latewood percentage and mostly negatie correlation with the content of extractives;there was mostly negative correlation between basic density and tracheid length,width,diameter,diameter-width ratio,But it was positive correlation with double wall thickness,length-width ratio,double wall thickness -diameter ratio.There was significant negative correlation between tracheid mocrofibrillar angle and tracheid length.The correlation coefficient between tracheid length of earlywood, latewood and microfibrillar angle was negative value at different tree height within trees, and which was significant at 0.01 level.The juvenile period of loblolly pine was about 12 years old.The difference of latewood percentage,tracheid length,tracheid diameter,tracheid double wall thickness, tracheid length-width ratio and basic density between juvenile and mature wood were significant at 0.01 level.The difference of annual ring and tracheid width between juvenile and mature wood were significant at 0.05 level.It indicated that the difference of wood characteristic between juvenile and mature wood was larger,so we had to combine material characteristic of both to use at wood utilization.From the tracheid morphology and basic density,the content of extractives,it suggested that the loblolly ping was suitable for paper making and pulping.