卧龙自然保护区林隙干扰特征

 林隙干扰对森林的结构和多样性的维持具有重要意义。对五一棚周围林隙干扰格局和林隙特征进行了3条样线调查，样线总长度为4.4 km。结果表明：1)本区以小型林隙干扰为主，林隙平均密度为12.5个?km-1，林隙的分布格局在阳坡和山脊为集聚分布，阴坡近均匀分布；林隙形成木以针叶树为主，岷江冷杉(Abies faxoniana)、铁杉(Tsuga chinensis)和糙皮桦(Betula utilis)在形成木的数量和径级组成上均居前列。2)林隙形成木的腐烂等级分布揭示出林隙形成木的形成方式和种类组成均随时间变化。表现为针叶树组形成木对林隙的贡献随时间降低，阔叶树组反之；砍伐和倒木是早期林隙形成的主要方式，而枯立和折干是近期林隙形成的主要方式。3)林隙木形成方式关联度分析结果为砍伐与倒木、折干与倒木之间存在显著负关联，林隙其它各形成方式之间的关联不显著，但砍伐与其它形成方式的负联结系数均较高。

CHARACTERISTICS OF CANOPY GAP DISTURBANCE IN WOLONG NATURE RESERVE

Canopy gap disturbances are important processes that maintain forest structure and diversity. We investigated the distribution and characteristics of canopy gaps in Wolong Nature Reserve around Wuyipeng, Sichuan. The results showed that small-scale gaps were the predominant types of disturbance. The average gap density was 12.5 km -1 . The distribution pattern of gaps was aggregated on south facing slopes and was approximately homogeneous on north facing slopes. Conifer trees were the primary gap-makers in this forest that was dominated by Abies faxoniana, Tsuga chinensis, Betula utilis, both in abundance and diameter rank. The decay class distribution of gap-makers indicated that the mode of gap formation and gap-maker species changed with age of the forest; the contribution of conifer species to gap formation decreased with time and broadleaf species increased. Moreover, the proportion of gaps caused by cutting and tree falls decreased while the proportion caused by standing dead and broken trunks increased. Association analysis of the mode of gap formation showed that there were significant negative associations between trees that were cut and tree falls and between snapped trunks and tree falls. Association coefficients for trees that were cut were relatively high with all other modes of gap formation, but there were no other significant associations between other modes of gap formation.