Aboveground biomass, ANPP and stem volume of birch stands in natural restoration process of subalpine secondary forest in Western Sichuan
川西亚高山次生桦木林恢复过程中的生物量、生产力与材积变化

Aboveground biomass, ANPP and stem volume of coniferous plantations have been studied in many papers in subalpine region of Western Sichuan, China. However, very few were reported about natural secondary birch forests (Betula spp.), which have become dominant types after over exploitation of old growth coniferous forests from 1950s to 1980s in this region. Aboveground biomass, aboveground net primary productivity(ANPP) and stem volume in birch forests with different stand age were calculated with allometric relationships and one-way tree volume models, respectively, by sampling stands with different age as a substitute for time series. The results indicated that aboveground biomass of tree layer as well as the average single tree increased with the increasing of stand age. Aboveground biomass of tree layer reached its peak at the 30 years old stand, that was 7.88 t?hm-2?a-1, and then slowed down gradually. Average individual aboveground biomass reached its maximum at the 30 years old stand, that was 1.13 kg?a-1. Stock volume of tree layer rose with the increasing stand ages, and the mean annual increment reached its maximum at the 50 years old stand, that is 3.78 m3?hm-2, while the current annual increment reached its peak at the 30 years old stand, that is 6.07 m3?hm-2. Average individual stem volume also rose with the increasing stand ages, both mean annual increment and current annual increment reached the peak at the 50 years old stands.