Woody debris storage and its distribution of dark coniferous forest in the alpine-gorge area

Woody debris,including coarse woody debris and fine woody debris,constitute a large component of forest biomass and play an essential role in forest biodiversity and material cycling in many forests. Many studies have been focused on the function,decomposition,formation,and storage of coarse woody debris,and their relations with forest regeneration under altitude 3000 m. Woody debris especially fallen and dead trees are often involved in the formation of a forest gap and forest regeneration,showing different distribution patterns from the forest gap center,and gap edge to a closed canopy. Compared to other forests,the dark coniferous forest ecosystems above altitude 3000 m can be limited more strongly by low temperature and natural disasters; therefore the forest regeneration can be more dependent on woody debris.Far less information has been available on woody debris storage and the distribution patterns that are affected by forest gaps in the dark coniferous forest. Accordingly,foe this study,we selected a typical primary forest of Minjiang fir( Abies faxoniana) in an alpine-gorge area in the eastern Tibet Plateau and western Sichuan. We analyzed woody debris storage and its distribution characteristics with different decay classes and diameters from forest gap center and gap edge to closed canopy. The results showed that woody debris storage was 53.00 t / hm~2 in the dark coniferous forest,and which in closed canopy was greater than that in forest gap and forest edge. Log showed the greatest storage compared to other coarse woody debris,and stump storage accounted for less than 1% of total coarse woody debris storage. The woody debris whose diameteris greater than 40 cm accounted for 76.15%,74.55%,and 75.68% of total woody debris storage in the forest gap center,gap edge,and closed canopy,respectively. No significant differences were observed in coarse woody debris with different diameters in the forest gap center,gap edge and closed canopy. The storage of woody debris with diameter 20-30 cm was significantly greater in the forest gap center than at the forest edge. The storage of woody debris of decay classes III and IV accounted for 50.02% in the forest gap center,55. 84% at the gap edge and 62. 90% in a closed canopy. No significant differences were found in coarse woody debris of different decay classes in the forest gap center,gap edge,and closed canopy. In contrast,the storage of woody debris of decay classes IV and V at the forest edge was signif