[Gap features of subalpine dark coniferous forest in Wolong Nature Reserve]

This paper studied the size structure and formation pattern of gaps and the characteristics of gap makers (GM) in subalpine dark coniferous forests in Wolong Giant Panda Nature Reserve, Sichuan Province, China. The results showed that the gap density was 18.5 per hm2, and the area of canopy gap and extended gap accounted for 28.4% and 60% of total forest area, respectively. Canopy gap varied from 10 m2 to 1134.7 m2, and expanded gap varied from 84.11 m2 to 1646.3 m2. Canopy gaps and expanded gaps had an average area of 153.45 m2 and 324.34 m2, respectively. The average number of gap makers (GM) per gap was 5.14, and only 8.1% of all gaps were created by just one GM. The order of GM contributed to gap formation was trunk snap > uproot > standing death > branch breakage. Abies faxoniana, Tsuga chinensis, and Betula utilis were the major gap makers, while Abies faxoniana in the canopy layer with 60-70 cm DBH and 30-35 m high had the greatest probability of gap making.