Abstract: We examined the current status and predicted future dynamics of the populations of Picea asperata, P. purpurea, and Abies fargesii var. faxoniana in the spruce-fir forests in the Taohe National Nature Reserve, aiming to provide a theoretical basis for the conservation and management of spruce-fir forests in water source conservation areas of the upper reaches of the Yellow River. We employed population structure diversity analysis, survival curve construction, survival function analysis, Logistic model fitting, population dynamic analysis, and potential community dynamic structure simulation to elucidate age structure and dynamic characteristics of these populations. Results showed that the age structures of P. asperata, P. purpurea, and A. fargesii var. faxoniana populations exhibited a pyramid shape, characterized by smaller at the top and larger at the bottom. All the examined populations had positive growth indices greater than zero, indicating they were currently growing populations. P. purpurea and A. fargesii var. faxoniana populations showed relatively weak buffering capacity against disturbances during their growth. Based on calculations involving individual numbers and basal area, we found that P. asperata population possessed both maximum environmental carrying capacity and maximum growth rate while occupying an absolute dominant position currently. Both P. purpurea and A. fargesii var. faxoniana populations demonstrated greater growth potential than P. asperata population. All existing communities as well as simulated potential communities displayed a growing structural pattern. The mixed communities exhibited the lowest growth rates while potential single-species communities dominated by P. purpurea showed the highest growth rates. Differences in characteristics and growth rates among three dominant species within current communities pose certain survival risks, and may affect the succession direction. Appropriate artificial intervention measures should be implemented to optimize population structures, which would help enhance resilience against future external disturbances.

Key words: spruce-fir forest, survival analysis, population dominance growth, community structure, diversity index