长苞铁杉林林隙自然干扰规律

从林隙的大小结构、形成方式及形成木的数量特征等几个方面 ,对长苞铁杉纯林及混交林林隙干扰状况进行了对比研究 .结果表明 :纯林冠空隙 (CG)平均面积为 16 .4 6m2 ,扩展空隙 (EG)平均面积为 96 .98m2 ,混交林CG、EG平均面积分别为 6 9.75m2 和 2 32 .93m2 ;在长苞铁杉纯林中 ,林隙主要以枯立木形成为主 ,占总形成木的一半以上 ,且以单株形成木和多株形成木综合形成 ,形成木径级主要集中在 2 0～ 4 0cm之间 ;混交林林隙以干基折断为主 ,且多由双形成木形成 ,由双形成木形成的林隙占林隙总数的 4 4 % ,形成木以 30～ 4 0cm径级的占最大比例 ,占形成木总数的 4 3.2 4 % ;纯林及混交林形成木高度都主要集中在 2 0～ 30m之间 ;形成木物种组成的比例大小基本上与其主林层树种所占的比例相对应 ;纯林林隙大多处于林隙发育的前、中期而混交林林隙则多集中在林隙发育的中后期 .图 3表 5参 19

GAP NATURAL DISTURBANCE REGIME IN TSUGA LONGIBRACTEATA FOREST

The characteristics and disturbance status of gaps in pure and mixed Tsuga longibracteata forests, including gap size, gap formation and the numbers of gap makers were studied. The results indicted that the size of canopy gaps(CG) in pure forest and mixed forest were 16.46 m 2 and 69.75 m 2, and the size of extended gaps(EG) were 96.98 m 2 and 232.93 m 2, respectively. Most gap makers of pure forest were stems, which accounted for more than 50% of all gap makers. In pure forest most gaps were formed by one or more than one stems and the diameter of most gap makers ranged from 20 to 40 cm. The most popular manner of gap formation was stem breakage at trunk base in mixed forest, of which two-gap-maker gaps were the majority, and the diameter of most gap makers varied from 30 to 40 cm. Both the height of gap makers in the two forests ranged from 20 to 30 m and the percentages of gap maker species were accordance with their species in main tree layer. Most of gaps in pure forest were at prophase and metaphase while most gaps in mixed forest were at metaphase and anaphase. Fig 3, Tab 5, Ref 19