银杉种群的空间分布格局

Spatial Distribution Pattern of Cathaya argyrophylla Population

银杉（Ｃａｔｈａｙａａｒｇｙｒｏｐｈｙｌｌａ ＣｈｕｎｅｔＫｕａｎｇ）种群的空间分布格局受银杉种群本身的生物学特性、种群的年龄和更新方式等及群落内小环境的共同影响。在老龄种群内，多表现为集群分布；在较年轻的种群内，多为随机分布。气候和立地条件基本一致时，群落内岩石的覆盖与土壤侵蚀形成的小环境，对银杉种群的空间分布类型和格局规模有显著影响；甚至在同一个林窗内，林窗中心和林绿附近不同的光照条件，对银杉的分布格局都有影响。银杉种群的空间分布格局受群落学特征的影响主要体现在群落种类组成和结构上。银杉作为共优种，在群落内的分布受制于其他共优种，特别是常绿阔叶树种。在各种银杉群落中，就银杉种群而言，光因子可能是影响其生存，进而影响其分布格局的主导因子。银杉种群集群分布的格局规模虽在各群落种群间差异明显，但大多在面积小于１６ｍ２的较小尺度下发生。

Cathaya argyrophylla Chun et Kuang is a Chinese endemic rare species distributed in Sichuan,Guithou, Guangxi and Hunan Provinces. It is considered as an endangered crop and is listed in the China Red Data of Plants due to its very limited resources. The distribution pattern of C. argyrophylla population was related to its biological characteristics such as the age structure and regeneration mode, and the microenvironments. In the old forests, gaps were abundant and occupied by variable-aged individuals of C. argyrophylla,resulting in a contagious distribution pattern. In the young forests random distribution pattern was more often found. Under the same climatic and site condition, the heterogeneity of microenvironments resulting from the different degree of rock cover and soil erosion significantly affected the type and scale of distribution pattern ofC. argyrophylla population. Even in the same gap, the center and foe edge could have different effects on the distribution pattern due to the uneven sunlight illuminance. As one of the codominants, the distribution of C. argyrophylla in communities was affected by other dominants, especially by the evergreen tree species. Light was the major factor determining the distribution pattern of C. argyrophylla in various communities. The pattern scale of contagious distribution of C. argyrophylla population was mostly less than 16 m2, although it differed among communities.