翅果油树(Elaeagnus mollis)群落的种间分离

Interspecific segregation in Elaeagnus mollis communities

在野外对山西翅果油树群落31个样方内所有基径≥1cm的灌木绘制空间分布图,应用最近邻体法判定每个个体的最近邻体植株,然后采用N×N最近邻体列联表及其截表(2×2最近邻体列联表)的方法,研究翅果油树群落所有灌木的种间分离规律。结果表明:该群落中随机毗邻种对占绝大多数(80.94%),正分离种对较少(18.78%),负分离种对极少(0.28%)。呈负分离的极少数种对是一些个体较小的小灌木,它们多为群落的伴生种,具有相近的生境需求,较激烈的种间竞争可能导致它们随机或均匀分布,因此这些种对表现出负分离;较大的个体之间容易发生正分离,因为它们大多是群落的建群种或优势种,具有强的适应能力和竞争能力。从星座图上可清晰地看到种间分离在不同种之间存在一定的差异。另外,引入群落全面分离这一新概念,并应用χ2检验进行检验研究了翅果油树群落中所有物种的全面分离规律。结果表明,翅果油树群落内38个物种互相交错分布,是全面不分离的。

Elaeagnus mollis is an endemic tree species in China and is ranked the second-class for protection of rare and endangered plants. It grows in a form of large shrub or dwarf tree and its distribution in China is restricted in Shanxi and Shaanxi provinces, and mostly in the south of Luuliang Mountains and west of Zhongtiao Mountains of Shanxi. Community of E. mollis is one of the typical vegetation types in the hills and lower-mountains of southern Shanxi. Interspecifie relationship is an important factor affecting community composition, structure, function and dynamics. In order to understand the role of interspecific segregation in E. moll,s communities, we investigated 31 quadrats of E. mollis communities in field, and drew a distribution map for all shrubs whose basal diameter is greater than lcm. The nearest neighbors of each individual were obtained by using the nearest neighbor＇ s method. The interspecific segregation was studied with an N×N nearest-neighbor contingency table and a 2×2 nearest-neighbor contingency sub-table. The result of interspecific segregation indicated that most of the species-pairs are randomly segregated （80.94%）, some species-pairs are positively segregated （18.78%）, and only a few species-pairs are negatively segregated （0.28%）. Negative segregation may occur between a few dwarf shrubs that have similar habitat requirements, which are mostly companion species in communities. Intensive interspecific competition may result in random or uniform distribution, therefore, such species-pairs are apt to be negatively segregated. Large individuals that are dominant or constructive species in communities tend to be positively segregated with other large arbors, due to their strong capacity in adaptation and competition. The constellation diagrams showed clearly the difference of interspecific segregation among the various species. In addition, we introduced a new concept the overall segregation. The overall segregated pattern in all species in the communities was studied by Z2 test based on the N×N nearest-neighbor contingency table. The result showed that 38 species in study overlap in distribution and are characterized by overall non-segregation.