云南松球果延迟开放及其植冠种子库

摘要

Canopy seed banks and serotinous adaptations are particularly prominent in fire-prone ecosystems.In this study,we recorded the number of open and closed cones in a P.yunnanensis forest,we observed the ripening year of the cones,and investigated the response of closed cones to high temperatures and forest fires.Closed cones could be retained in the canopy for seven years,and open cones nine years.The germination rate of closed cone seeds decreased with increased serotiny time.The germination rate of seeds from cones retained in the canopy for nine years was 2.9％.There were about 100,000 viable seeds in the canopy seed bank per 100-m2 plot,which was two times higher than the annual seed production.From every cohort,some of the cones would release seeds,and all seeds were released within eight years after maturation.The serotinous cones of P.yunnanensis could be induced to open with high temperatures (over 40 ℃).With increasing temperatures,the time to open the cones decreased.The number of released seeds in post-fire plots was 2.6-fold higher than in unburned plots.In addition,the rate of germination was (69.8±22.8)％ for released seeds in post-fire plots.These results suggest that P.yunnanensis is a weakly serotinous species.Fire significantly increased the release of seeds form the canopy seed bank,whereas the serotiny time was similar to seed longevity in closed cones.Furthermore,released seeds in the post-fire and unburned plots originated from cones that ripened in different years.In sum,the serotinous cones for P.yunnanensis were adapted to fire in fire-prone habitats.%植物果实成熟后在植冠中宿存延迟鳞片开放释放出种子,是易火生境中植物的一种常见适应性状.以分布于昆明西郊的云南松为研究对象,调查了云南松植冠中保存球果的数量、鳞片开闭状况、球果年龄分布和球果内种子的萌发率,以及宿存闭合球果鳞片开放对高温和火烧的响应.结果显示:云南松植冠中除有当年成熟球果外,还有1a到7a前成熟的鳞片闭合球果,以及1a到8a前成熟的鳞片开放球果.宿存闭合球果中有可萌发的种子,种子的萌发率随球果宿存时间的延长而下降,宿存9a球果中的种子平均萌发率仅为2.9％.每100m2林地的植冠中储存有大约105粒有活力的种子,是近3年平均种子产量的2倍.宿存的各年球果在宿存期间每年会有一些球果的鳞开放释放出种子,一般在成熟后的8a内所有球果逐渐开放释放出种子.40℃以上的温度可诱导球果鳞片开放,球果开放时间随着烘烤温度的升高而缩短.过火后云南松释放种子的数量约为非过火地段年均释放种子量的2.6倍,过火地段云南松释放种子的萌发率为(69.8±22.8)％.研究结果表明,云南松具有非严格植冠种子库,地面火可诱导植冠中的闭合球果鳞片开放释放种子,球果在植冠中最长宿存和延迟开放的时间与种子存活的时间基本一致;每年自然释放和过火后释放的种子都由多年成熟的种子组成;云南松球果延迟开放可能与生境易发生林火有关.