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以种群生命表和生存分析理论为基础,采用空间代替时间法和分段匀滑技术,编制梵净山自然保护区珙桐天然种群特定时间生命表,绘制其死亡率曲线、消失率曲线、存活曲线和生存函数曲线,分析种群数量动态变化。结果表明:珙桐种群结构存在波动性,趋于DeeveyⅢ型,其幼年阶段的个体较丰富;珙桐种群死亡率和消失率曲线变化趋势基本一致,在这一发育过程中有两个死亡高峰,一个出现在幼苗向幼树的过渡期(Ⅰ龄级→Ⅱ龄级),另一个出现在从中龄向老龄过渡的阶段(Ⅷ龄级→Ⅸ龄级);种群生存分析表明,珙桐种群的生存率单调下降,累计死亡率单调上升,Ⅷ龄级后,种群生存率小于8%,累计死亡率大于92%,危险率超过生存率;4个生存函数曲线表明,梵净山珙桐有前期锐减、中期稳定和后期衰退的特点。幼苗和中龄级个体的不足是导致珙桐濒危的重要原因。
Based on the population life table and survival analysis theory, the spatial time-substitution method and the segmented smoothing technique were used to compose the specific time-table of the natural populations of Davidia involucrata in Fanjing Mountain Nature Reserve, and the mortality rate curves and the disappearance rate curves were drawn and survived Curve and survival function curve to analyze the dynamic change of population quantity. The results showed that the structure of Davidia involucrate population fluctuated and tended to Deevey Ⅲ type, and the individuals in the juvenile stage were more abundant. The trend of mortality and disappearance rate of Davidia involucrata population was basically the same. There were two death peaks in this development, One appeared in the transitional stage of seedling to young tree (Ⅰ grade → Ⅱ grade), and the other appeared in the transition from middle age to old age (Ⅷ age → Ⅸ age). The population survival analysis showed that the Survival rate monotonically decreased, cumulative mortality monotonically increased, the survival rate of the population was less than 8%, the cumulative mortality rate was more than 92%, the risk rate exceeded the survival rate after Ⅷ age class; Sharp decline, mid-term stability and the characteristics of late decline. Lack of seedlings and middle-aged individuals is an important cause of endangered Tong.