甘肃文县珙桐群落优势种的种间联结性测定

根据２×２联列表，应用Ｏｃｈｉａｉ指数、Ｄｉｃｅ指数和Ｊａｃｃａｒｄ指数等技术，测定甘肃文县珙桐群落的８个优势种群间的联结性，以半矩阵图表达测定结果。研究表明，珙桐群落种间联结较复杂。群落的８个优势种２８个种对间有１０对存在显著的正联结（Ｉ０＞０．４）。其中珙桐与生态习性相似的包果石栎、千金榆表现为极显著正联结，白桦与亮叶桦亦为极显著正联结。群落中１５个种对存在显著的负联结（Ｉ０＜０.７），约占总种对数的５４％反映出该区域珙桐群落的次生性和年青性。珙桐、包果石栎、青冈与白桦、青冈与亮叶桦生态习性差异较大，表现为极显著的负联结。表明生态习性相似、对环境要求相似、亲缘关系较近的植物种相伴随出现的几率较大。

Studies on the Interspecific Association of Davidia involucrata Community's Dominant Species in Wen County of Gansu

A series of techniques including the analysis of Ochiai, Dice and Jaccard indices were used based upon 2×2 contingency tables to determine the interspecific association of the 8 dominant species in the Davidia involucrata community in Wen county of Gansu province. The result is expressed in the form of semi-matrix figure. The result indicates that the interspecific association is complicated. There are 10 couples of the 28 couples among 8 dominant species which relationship are significantly positive (I_0> 0.4). The relationship between Davidia involucrata and Lithocarpus cleistocarpus, Carpinus cordata, which have similar ecological habits, are great significantly positive. The relationship between Belula platyphylla and Betula luminifera is great significantly positive too. There are 15 couples (of 54 % the total) which relationship are significantly negative (I_0 < 0.7). It indicates that these Davidia involucrata communitise has secondary and young characteristics. The relationships between Davidia involucrata, Lithocarpus cleistocarpus, Quercus glauca and Betula platyphylla, Betula luminifera and Quercus glauca, which ecological habits are different, are great significantly negative. It indicates that the probability of the presence of accompanying species will be high, if the species have similar ecological habits, have similar environmental requirements, and are closely evolutionarily related.