黄龙山白桦种群结构及其时间序列预测分析

Study on the population structure and time sequence prediction of Betula platyphylla in Huanglong Mountain

【目的】阐明黄土高原南部地区白桦种群未来的发展趋势,为其合理经营利用提供依据。【方法】以群落物种重要值为依据,通过聚类分析,将黄龙山地区的白桦林划分为4个群落类型,每个类型中的全部白桦个体为一个种群,分析白桦不同种群的年龄结构、存活曲线及静态生命表,并应用时间序列模型预测了种群的发展趋势。【结果】黄龙山地区白桦种群幼龄个体较少,中老龄个体较多,基本呈衰退趋势;种群A幼龄株数相对较多,有一定更新能力;种群C、D衰退特征较为明显,其中种群D只在Ⅲ、Ⅳ龄级具有一定数量个体,几乎没有更新幼苗。种群A、B、C、D的生命表和存活曲线表现出相似的特征,即Ⅰ、Ⅴ、Ⅵ龄级死亡率高,除种群A外,标准化最高存活量均出现在Ⅲ或Ⅳ龄级。时间序列预测分析表明,在未来20,30,40和50年中,多数种群均呈现幼龄个体减少而老龄个体增加的态势,老化趋势较为明显。【结论】黄龙山白桦种群表现出明显的衰退特征,属于该地区的过渡种群,逐渐会被更加稳定的松栎混交林所取代,应根据各种群的特点采取不同的经营措施,以促进群落演替。

[Objective] Betula. platyphylla forest is the general forest type distributed in the south Loess Plateau. In order to characterize the age structure and dynamics of the B. platyphylla population and to provide some scientific basis for reasonable exploitation and utilization, 18 sample fields in Huanglong Mount were investigated and studied. [Method] Using Statistic software,cluster analysis was made based on the importance value of every species in different sample fields,and then these sample fields were seg mented into 4 community types when the linkage distance was 0.8, and all B. platyphylla individuals of every type were regarded as a population. The age structure, static life table, survival curve and the time sequence prediction of number dynamics of different B. platyphylla populations were studied based on the investigation. [Result] Most B. platyphylla populations had relatively small young individuals but relatively rich old ones, so they presented declining tendency. Only population A, which had comparatively rich young individuals,had limited ability of regeneration. Population C and population D both showed more obvious declining tendency,and the latter just had individuals on Ⅲ and Ⅳ class. Even under different environmental conditions, static life table and survival curves of 4 different populations showed similar features：relatively high mortality rate was displayed in age class Ⅰ ,Ⅴ and Ⅵ,and except population A,the maximum standard living number was found on age class Ⅲ or Ⅳ of the other populations. Time sequence prediction models for different populations after 20,30,40 and 50 years indicated that the number of old individuals would increase and that young individuals would decrease, all 4 populations showed apparently aging tendency. [Conclusion] B. platyphylla population would be substituted gradually by Pinus tabulaeformis and Quercus wutaishanica forest which is more stable, and all the analyses indicate that B. platyphylla is transient population in this area. And in order to promote the community succession, various management measures should be taken according to the features of different B. platyphylla populations in Huanglong Mountain.