水杉原生母树种群结构与动态

Population structure and dynamics of Metasequoia glyptostroboides parent trees

为揭示水杉(Metasequoia glyptostroboides)原生母树种群的生存现状与数量动态,预测未来种群的发展趋势,基于野外种群调查数据,对种群结构与动态进行探讨。结果表明:(1)种群自然更新不良,DBH<40 cm的个体仅占种群个体总数的4.5%,纺锤型的径级结构表明种群属衰退型。(2)种群幼龄个体存活率较低,中龄个体生存能力强,Ⅷ龄级之后存活量快速减少,存活曲线接近Deevey-Ⅲ型;种群死亡率和消失率整体上都随龄级增大而升高,均在Ⅸ龄级达到最大值。(3)生存分析表明,种群呈前期略减、中期波动、后期衰退的特征;幼龄阶段是种群生活史中的脆弱环节,Ⅷ龄级之后种群进入生理衰退期。(4)时间序列预测表明,未来8年期间种群幼龄和中龄个体不断减少,老龄个体渐增,种群整体的长期稳定性难以维持。总之,幼龄个体严重缺乏是种群趋于衰退的主要原因,保持适当的人工辅助恢复和加强现有植株及其生境保护是种群更新复壮的关键。

The population structure and dynamics characters reflect the survival status of plant species and their interactions with environment. Metasequoia glyptostroboides, a famous living fossil, is one of the greatest botanical discoveries of the 20th century. Even extensively planted around world, we still know little about the current population status of M. glyptostroboides parent trees in the natural ecosystem. In this study, the population structure and dynamics were analyzed based on the investigation data on the natural population of M. glyptostroboides parent trees. The results showed that ： （ 1 ） The natural regeneration of M. glyptostroboides was extremely weak and the individuals 〈40 cm DBH （diameter at breast height） only accounted for 4.5% of the total population. The spindle-shaped DBH structure indicated a depression tendency for M. glyptostroboides population. （2） The survival rate of the population was low for young individuals and the survival ability of middle aged individuals were strong. After reaching Ⅷ class age, the number of survival individuals decreased greatly. The survival curve of the population approached to Deevey-Ⅲ type. （3） The population showed a slight decrease at the early stage, fluctuation at the middle stage and depression at the late stage. The young stage was the fragile period during the population life history. After the Ⅷ class age, the population entered the period of physiological recession. （4） The time sequence analysis predicted that the number of young and middleaged individuals would gradually decrease and old individuals would increase for the upcoming eight years. It＇ s very hard to maintain the long-term stability of M. glyptostroboides population.Our results indicated that the extreme lack of young individuals was the main reason for the depression tendency of M. glyptostroboides population. In order to restore population, it＇ s urgent to provide proper artificial aid recovery and reinforce protection of existing parent trees as well as their habitats.