| Subalpine coniferous forest was one of the most important areas of timber supplying and the center of biodiversity. It was a principal part of Natural Protection Project in western Sichuan and important ecological defense to the upper reaches of the Yangtze River, played the key roles in developing economics, and was one of the ideal locations to study forest ecosystem. Unfortunately, most of the subalpine coniferous forests had been destroyed, and the secondary vegetation hardly fulfilled the ecological functions that the primary subalpine coniferous forests did. In the past decades, lots of scientists had persisted in studying on it and great deals of achievements were got. However, the studies of forest dynamics based on gap were few. The purpose of this project was to offer basic data and theory for forest management by study of typical primary coniferous forest gaps in western Sichuan.In order to explore the functions of gaps on forest dynamics and biodiversity protection in the subalpine coniferous forest of western Sichuan Province, the survey of gaps and community had been carried out in typical primary coniferous forest of Dawodang in Wanglang Nature Reserve (DWNR). Natural disturbance regimes of gaps,tree species regeneration responses to gaps, and some structural characteristics of stands in the primary coniferous forests were studied. The patterns of gap disturbance were investigated. Some parameters related to gap disturbance such as size and age structure of gaps, distribution patterns of gaps, diameter at breast height (DBH), height and ratio of crest inclination (RCI) of gap borders (GB), diameter, height and decay classes of gap makers (GM), the number of gap makers in forming a gap, turnover rate of gap disturbance, manners of gap formation as well as percentage of gap area in the primary coniferous forest landscape were described and discussed in detail. At last, some suggestions of managing subalping coniferous forest were made. The results indicate:Most of the GMs were bigger canopy trees in the primary coniferous community. The dead manners of GMs were up-rooting treefall (U), standing death (S, the remnant trunk were more than 10m) and trunk snapping which were separated into brakeage on trunk (BT, the remnant trunk were rather than 2m) and breakage at trunk base (BB, the remnant trunkwere in the range of 2m and 10m), and their contribution to form gaps was: BB>BT>U >S. The oldest GM was 110 years, the latest was 4 years, most of the GMs dead in tow decades (52.47% of the total), and the averaging age of GMs was 28.02 years. Most felled trees were oriented to north, northwest or northeast. There were some seedlings or saplings on lots of GMs (43.83% of the total), especially on the GMs of 60 years and more. The averaging sizes of EG and CG made by one GM were 71.68 m2 and 154.14 m2.There were 789 GBs in 83 gaps, the DBHs of GB accorded well to that of canopy trees while the height of GB were shorter than that of the canopy trees in the community. The species RCI variances of GBs were significant at 0.041 level. It was feasible to replace the height of gap with that of GBs of the gap. The largest number of GBs in one gap was 17 while the smallest was 5, averaging 9.51 GBs per gap.Most of the disturbances in the primary coniferous forest were small. Almost half of these gaps were made by one tree (46.99 % of the total). The largest number of GM in one gap was 5, averaging 1.95 trees per gap. Most of the gaps were elliptic in horizontal (63.86 % of the total), and they were cylinder in verticality, which was formed by the rotated irregular hyperbola. Most of the spread of gap were smaller.The linear percentage of EG and CG vs. sampled trips were 39.91% and 18.73 %, and the linear percentage of CG vs. EG was 46.92 %. The size percentage of EG and EG vs. sampled trips were 41.62 % and 19.35 %, and area percentage of CG vs. EG was 46.50 %, averaging 13.83 gaps per hectare. The rate of making gap was 0.13 N·hm-2 · a-1, which meant 0.13 gaps would be made on one hectare land in...
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