天然珙桐种群结构与动态特征在高低纬度地区的差异

作为我国特有的珍稀濒危物种，天然珙桐（Davidia involucrata Baill.）的种群特征已被众多文献所报道，但纬度变化对其结构和动态的影响还未见研究。本研究对比分析了四川平武县和云南滇东北两个地处相似经度而不同纬度区域的天然珙桐种群的年龄结构动态指数、静态生命表、生存力及其数量变动差异。结果表明：高、低纬度种群结构均为增长型，两地种群的存活曲线均属于Deevey-Ⅱ型，与高纬度的平武县种群相比，低纬度的滇东北珙桐种群表现出更高的增长趋势和较强的种群抗干扰能力；种群动态特征分析结果表明，高纬度的平武县珙桐种群幼龄级个体生长较好，中龄级个体竞争激烈，低纬度的滇东北种群幼龄级个体死亡率高，中龄级个体生长稳定。综上，天然珙桐种群结构和动态特征存在纬度差异。低纬度地区的珙桐幼树存活率低，但成年个体生长良好；高纬度地区的珙桐幼树生长较好，但中龄级个体死亡率高。

Differences in Population Structure and Dynamic Characteristics of Davidia involucrata Baill. Between High and Low Latitude Regions

Davidia involucrata Baill. is a rare and endangered tree species which is endemic to China. Though population characteristics of D.involucrata have been reported by many studies， the effect of latitude on the structure and dynamic characteristics of D.involucrata has been largely neglected. In this study， we compared the variance of the age structure dynamic index， static life table， viability and quantity alteration of the populations between high latitude region（Pingwu） and low latitude region（Northeastern Yunnan）. Our results showed that the population structure in Pingwu and Northeastern Yunnan were of growth type， the survival curve of the two D.involucrata populations was of a Deevey-Ⅱ type， and the population in Northeastern Yunnan displayed a higher growth trend and stronger anti-interference ability. Moreover， the population dynamics analysis revealed that younger individuals grew better in Pingwu and the middle-aged individuals competed fiercely. By contrast， younger individuals in Northeastern Yunnan population had high mortality， middle-aged individuals grew stable. Thus， based on the abovementioned findings， we conclude that latitude differences could affect population structure and dynamic characteristics of D.involucrata. The habitats of D.involucrata population at low latitude were suitable for middle-aged individuals to survive but not for younger individuals； younger individuals of D.involucrata populations at high latitude grew better， and higher mortality rate was observed in middle-aged individuals.