藏东南亚高山冷杉林林隙特征与干扰状况研究

Characteristics and disturbance status of gaps in subalpine fir forest in Southeast Tibet.

从林隙的大小结构、干扰频率、形成方式及林隙内形成木的数量特征等几个方面 ,对藏东南色季拉山亚高山冷杉林的典型群落类型———藓类冷杉林的林隙干扰状况进行了分析 .结果表明 ,在冷杉林中 ,扩展林隙 (EG)和冠空隙 (CG)的面积分别占林分总面积的 4 1 .73%和 1 4 .71 % ;平均每年有 0 .82 %的林分面积转化为扩展林隙 ,0 .2 9%的林分面积转化为冠空隙 ;每年 1hm2 面积上约有 0 .31个林隙形成 ;林隙的干扰周期为 34 5年 .在调查的 1 6个林隙中 ,共有形成木 (GM ) 78株 ,平均每个林隙中有 4 .88株 .形成林隙最主要的方式是形成木的折倒 ,其次为拔根和枯立 ,主要外力作用是大风 .当主林层林木直径达到 4 0～6 0cm、高度 1 5～ 2 0m时 ,形成林隙的可能性最大 ;同一林隙常常受到形成木多种死亡方式的影响 ,且形成时期各不相同 .藏东南亚高山冷杉林林隙由不同年代的多次干扰而形成 .

Characteristics and disturbance status of gaps,including gap size,disturbance frequency, forming patterns of gaps, and quantity of the tree in gap, in subalpine fir forest in Southeast Tibet were studied.The results showed that expanded gaps accounted for 41\^73% and canopy gaps accounted for 14\^71% of land area in the forest. Averagely, 0\^82% and 0\^29% of forest area were transformed into expanded and canopy gaps every year. The velocity of gap forming was 0\^31 ind·hm -2 ·yr -1 . The disturbance cycle of gaps was 345yr. Among 16 investigated gaps,there were 78 gap markers in total, and there were averagely 4\^88 trees in each gap. The main reasons of gap forming were gap markers fallen as well as uprooted and withered,and their external force was strong wind. The possibility of gaps forming reached the maximum while the diameter of arbors was 40～60 cm and the high was 15～20m in the main forest layer. Gaps were formed by many distubances in different age in the subalpine fir forest in Southeast Tibet.