Abstract:

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.

Key words: Small canopy gaps, Natural disturbance, Distribution pattern, Gap-maker, Association analysis