[Structural characteristics of Abies fabri forests at the upper reach of Yangtze River].
The structural characteristics of Abies fabri forest under different succession stages in Gongga Mountains at the upper reach of Yangtze River were studied. The results showed that in the mature Abies fabri forest, there existed abundant seeds and a few saplings of Abies fabri younger than 20 years, but only Abies fabri was the dominant regeneration species. In the poplar-fir mixed forest, the height growth of poplar and birch was very fast during first 30 years, and poplar and birch dominated rapidly over the canopy. Abies fabri had a lower growth rate and a strong shade-tolerance in its first growth stage, and could replace other tree species gradually. The cycle of mud-rock flow occurrence was above 100 years in the Gongga montane areas from elevation of 2800 to 3200 m. After mud-rock flow, poplar and birch often occurred and dominated, and there were only a small number of Abies fabri saplings in slash. Under natural condition, to recover Abies fabri forest would demand a long time, but this process could be controlled and improved by human activities.