湖北省榉树自然种群分布研究

对湖北省天然榉树的自然种群分布现状、种群特征及种群分布格局进行了研究。结果表明：湖北榉树资源主要分布在海拔500~1 000 m地带，不同程度地分割包围在谷底和山腰，地理分布点呈收缩集群分布，种群规模较小；采用方差/均值法对榉树地理分布格局类型进行分析，其值=1.66>1，表明其分布点的地理分布趋于集群分布。湖北榉树种群星散间隔的地理分布形式，使地理分布点间产生空间间隔，成为相互间基因交错的障碍，而较小的种群规模，增加了遗传漂变的机率，导致遗传上的不稳定性增加，影响种群的生存能力，这些是导致物种趋向濒危的重要原因。湖北榉树种群这种分布现状产生的原因，一方面是物种自身的生物学特性及对生境的特定要求所致，另一方面是由于人类对榉树资源的过度开发利用以及人类经济活动导致的生境片段化。应借助于人为帮助，改善生态环境，扩大其种群规模，促进不同种群之间的基因交流，以利保护。

STUDY ON THE NATURAL POPULATION DISTRIBUTION OF ZELKOVA SCHNEIDERIANA IN HUBEI

Natural population distribution status, population characteristics and population distribution pattern of natural Zelkova schneideriana in Hubei province were investigated in the present study. The results showed that Zelkova schneideriana resources in Hubei province mainly distributed in the altitude condition of 500-1 000 m,being divided or being surrounded in the bottom of valley and mountainside,and their geographical distribution showed a shrinking group pattern, with relatively small populations. Variance method and mean value method were employed to analyze the geographical distribution pattern of Zelkova schneideriana ,and the results indicated that its value was equal to 1.66 and larger than 1,which demonstrated that its geographical distribution appeared to be a grouping distribution. The scattered geographical distribution pattern of Zelkova schneideriana resulted in spatial interval distribution, which was a barrier for the gene crossing, while smaller populations increased the chances for genetic drift,leading to an increase in the heredity instability,and affecting the population viability. All these were the major reasons resulting in the species endangerment. The causes responsible for the distribution status of Hubei Zelkova schneideriana were,on the one hand, biological characteristics of species themself and its specific requirements for habitat, on the other hand,over-exploitation of Zelkova schneideriana resources by human beings and the habitat fragmentation resulted from human economic activities. Based on the evidences provided in the present study, the authors suggested that ecological environment should be improved, and populations enlarged so as to promote the gene intercourse among different population and thus to protect the species.