马尾松纸浆材材性变异和采伐林龄的确定

报道了马尾松木材管胞长度、管胞长宽比、基本密度和化学组分含量的变异规律。结合林木材积连年生长量给出了不同树龄材性的具体数值。管胞长度径向变异遵循“递增、趋于稳定”模式，纵向变异由基部向上先递增至７．３ｍ高度，而后递减至１９．３ｍ；管胞长宽比变异与管胞长度变化趋势一致。基本密度髓心附近较大，由髓心向外递减至最小值后再缓慢增加，并趋于稳定；基本密度纵向变异由基部向上递减，最大值位于树干基部。纤维素含量由髓心附近的３８．７５％（１～３轮）递增到２２轮处的４８．９８％，净增１０．４１％；木素、多缩戊糖和苯醇抽出物含量分别由髓心附近的２８．３５％，１４．３２％和６．６％递减到树皮附近的２４．７％，１０．２４％和１．２２％，３者依次净减３．６５％，４．０８％和５．３８％。马尾松木材幼龄期约１４～１８ａ，幼龄期前天然林管胞长度、长宽比和浸提后的基本密度大于人工林，幼龄期后则正好相反。基于不同树龄材性的变化，马尾松短周期纸浆林最低采伐林龄不得低于１５ａ。

Variation of pulpwood characteristics and cutting age of Masson pine

Eight plantation trees(20 to 26 years old)and 2 natural forest trees(54 and 55 years old) of Masson pine were collected in Forest Farm of Jingshan County,Hubei Province Tracheid lengths in radial direction first gradually increased and then levels off from pith to bark.It decreased along the stem height So did the variation in tracheid length wide ratio Basic density at the pith was bigger than that at the bark,and it firstly descended from pith to bark,then gradually asended and finally leveled off.It longitudinally descended from base to top Cellulose content increased from pith(38 57%)to near bark(46 98%) in 22 years old trees Lignin,pentosan and benzen alchol extractives contents decreased from pith(28 35%,14 32% and 6 60%) to bark(24 70%,10 24% and 1 22%) The juvenile period of the wood was about 14 to 18 years old Before the period,the tracheid length,length wide ratio and extracted basic density in trees of natural forests were greater than those in those of plantations After the period,the results were right converse Based on variations in the whole tracheid morphological features,basic density,wood chemical composition and the tree growth properties,the range of mature ages for pulpwood were from 15 to 30 years old