Abstract: The biomass dynamics, density dynamics, and density-dependent regulation of biomass dynamics in alder and cypress mixed forest were studied at Yangting County of Sichuan Province. The results show that the biomass of alder accords with logistic growth in the past 18 years. and that of cypress conforms to power function growth in tile Past 20 years. The densities of alder and cypress show a negative power function growth in the past 18 years. In the mixed forest, density-dependent death is tile key factor determining the dynamic, of population biomass. The mean individual biomass is approximately related to the density by the -3/2 power law, and the self-thinning indices of alder and cypress are -2.33 and -3.97, respectively. The increase in mean individual biomass is greater than its decrease caused by population density reduction. As a result, the biomass of the two populations still increases during the period of density-dependent regulation, and the biomass of cypress population increases more vigorously.

Key words: Alnus cremastogyne, Cupressus funebris, Density dynamics, Biomass dynamics, Density-dependent regulation, generalized additive model (GAM), the tropical Atlantic Ocean, longline fishery, Tweedie distribution, Pseudocarcharias kamoharai