Gross C L, Mackay D
Ecosystem Management, University of New England, Armidale, NSW 2351, Australia
Ecosystem Management, University of New England, Armidale, NSW 2351, Australia.
Ann Bot. 2014 Jul;114(1):85-96. doi: 10.1093/aob/mcu082. Epub 2014 May 20.
Olearia flocktoniae is an endangered shrub that was passively translocated from its natural ecosystem, where it has since gone extinct. This study aimed to determine sensitivities vital to populations persisting in human-created areas.
Population colonization, longevity and extinction were investigated over 20 years using 133 populations. Seed-bank longevity was determined from germination trials of seeds exhumed from extinct and extant sites via a 10-year glasshouse trial and by in situ sowing experiments. From 27 populations, 98 cohorts were followed and matrix models of transitions from seeds to adults were used to evaluate the intrinsic rate of population growth against disturbance histories. Ten populations (38 cohorts) with different disturbance histories were used to evaluate sensitivities in vital rates.
Most populations had few individuals (∼30) and were transient (<5 years above ground). The intrinsic population growth rate was rarely >1 and all but two populations were extinct at year 20. Seeds were short-lived in situ. Although >1000 seeds per plant were produced annually in most populations, sensitivity analysis showed that the transition to the seed bank and the transition from the seed bank to seedlings are key vulnerabilities in the life-cycle.
Seedling establishment is promoted by recent disturbance. Increasing the number of disturbance events in populations, even severe disturbances that almost extirpate populations, significantly increases longer-term population persistence. Only populations that were disturbed annually survived the full 20 years of the study. The results show that translocated populations of O. flocktoniae will fail to persist without active management.
弗洛克托尼亚木是一种濒危灌木，它从其天然生态系统中被被动迁移，此后该生态系统中的该物种已经灭绝。本研究旨在确定对于在人为创造的区域中持续存在的种群至关重要的敏感性。
利用133个种群，对20年间的种群定殖、寿命和灭绝情况进行了调查。通过为期10年的温室试验以及原位播种实验，从已灭绝和现存地点挖掘出的种子进行发芽试验，从而确定种子库寿命。对27个种群的98个同龄组进行跟踪，并使用从种子到成体的转变的矩阵模型，根据干扰历史评估种群增长的内在速率。利用10个具有不同干扰历史的种群（38个同龄组）来评估生命率的敏感性。
大多数种群个体数量很少（约30个）且是短暂存在的（地上存活时间<5年）。种群内在增长率很少大于1，到第20年时，除两个种群外，其他所有种群都已灭绝。种子在原位寿命较短。尽管大多数种群每年每株产生超过1000粒种子，但敏感性分析表明，向种子库的转变以及从种子库到幼苗的转变是生命周期中的关键脆弱环节。
近期的干扰促进了幼苗的建立。增加种群中干扰事件的数量，即使是几乎使种群灭绝的严重干扰，也能显著提高种群的长期持久性。只有每年受到干扰的种群在为期20年的研究中全部存活下来。结果表明，如果没有积极的管理，弗洛克托尼亚木的迁移种群将无法持续存在。
