祁连山大野口流域青海云杉种群数量动态

种群数量动态揭示了种群的结构特征及其潜在的驱动机制,有助于预测种群未来的动态,进而为森林生态系统的保护与恢复提供理论依据。本研究基于10.2 hm²青海云杉动态监测样地数据,以种群径级结构代替年龄结构,编制静态生命表,绘制径级结构图、存活曲线、死亡率曲线、消失率曲线和4个生存分析函数曲线,分析青海云杉种群数量特征,并利用种群数量动态变化指数和时间序列模型对种群数量动态进行预测。结果表明：（1）青海云杉种群的年龄结构近似于倒"J"型,幼苗和小树储量丰富;（2）种群存活曲线趋近于Deevey-Ⅱ型,为稳定型种群,死亡率曲线和消失率曲线变化趋势基本一致,均在第2、8龄级出现高峰期;（3）生存率曲线呈下降趋势,累计死亡率曲线呈上升趋势,死亡密度曲线缓慢下降,而危险率曲线逐渐上升,该种群具有：前期减少、中期稳定、后期衰退的生长特点;（4）种群数量变化动态指数V_pi>0,表明该种群属于增长型种群,V_pi''>0且趋近于0,则表明该种群趋近于稳定型;（5）时间序列预测分析表明,在未来2、4、6、8个龄级时间后,种群呈稳定增长趋势。研究显示,祁连山大野口流域青海云杉种群为稳定增长型种群,只要未来不遭受强烈干扰,种群数量会保持逐渐增长。针对该种群幼龄个体在前期的更新过程死亡率较高情况,建议在今后的经营管理中应重点加强对第1、2龄级植株生存环境的保护和改善,提高幼苗和小树的存活率。

Quantitative dynamics of Picea crassifolia population in Dayekou basin of Qilian Mountains

Picea crassifolia, a major constructive and dominant species in the subalpine montane forests of the Qilian Mountains, plays a vital role in preserving soil and water, regulating regional climate and maintaining ecological balance. Exploring the dynamics of plant population can reflect the current status of the population and its potential driving mechanisms, which helps to predict future population dynamics and provides a scientific basis for the conservation and restoration of the forest ecosystems in the Qilian Mountains. However, despite extensive research on this species, little is known about its population dynamics. To fill this gap, this study was conducted to reveal the population dynamics of P. crassifolia based on the community structure data from 10.2 hm² P. crassifolia dynamic monitoring plots. Specifically, we analyzed the population characteristics of P. crassifolia by preparing static life tables, plotting trail-level structure, survival curves, mortality curves, disappearance rate curves, and four survival analysis function curves. Notably, the diameter class structure rather than the age structure was used in this analysis. Moreover, the population dynamics trends were predicted by the population dynamics change index and time series model. The results showed that:(1) The age structure of the P. crassifolia population was roughly inverted J-shaped, with abundant seedlings and small trees reserves. (2) The survival curve of the population tended to be similar to the Deevey-II type, indicating that the population was a stable one, and the trends of mortality and disappearance rate curves were basically the same, both reaching the maximum at the second and eighth age classes. (3) The survival rate curve showed a significant downward trend; the cumulative mortality curve showed a significant upward trend; the mortality density curve decreased slowly, while the hazard rate curve showed an overall upward trend. Therefore, the growth of the population was characterized by a rapid decline in the early stage, stabilization in the middle stage, and decline in the later stage. (4) The dynamic index of population changes V_pi>0 indicating that the population was growing, V_pi''>0 and it is close to 0, indicating that the population tended to be stable. (5) The time series prediction analysis showed a stable population growth trend after the next 2, 4, 6, and 8 age classes of time. To conclude, the study shows that the population is a stable growing one and will keep growing gradually in size as long as it does not suffer strong disturbances in the future. The high mortality rate of young individuals early in the renewal process suggests that future management should focus on protecting and improving the growth conditions during the first and second age classes of the plants to improve the survival rate of seedlings and small trees.