Unraveling the roles of various ecological factors in seedling recruitment to facilitate plant regeneration

Unraveling the mechanisms causing restricted regeneration and limited
distribution range has become a core issue for biodiversity conservation.
Anthropogenic disturbances are changing a variety of ecological factors,
but how their relative importance varies across multiple regeneration
stages is still unclear even in a single species. In this study, we
focused on Metasequoia glyptostroboides, a relict species suffering a
severely restricted regeneration in the wild, and performed controlled
experiments using 54,600 seeds to investigate seedling emergence and
growth in both its natural and adjacent unoccupied habitats to disentangle
the roles of seed availability, interspecific competition and
herbivore/omnivore attack across early regeneration stages. Our results
showed that these factors mainly exerted their predominant effects at
initial regeneration stages. Compared with herbivore/omnivore attack, seed
availability and interspecific competition were the crucial factors
regulating seedling emergence. The first-year seedling survival rate was
only significantly influenced by interspecific competition, and the
survival of second-year seedlings was independent of all these factors.
Moreover, we detected similar impacts of these factors in the adjacent
unoccupied habitats to those in the natural habitats, indicating their
roles in limiting population expansion. Our findings provide some
suggestions to assist the natural regeneration and range expansion of M.
glyptostroboides, and our experiment design can be applied in the
assessment of endangerment causes for other endangered plants.

阐明导致受限更新与分布范围狭窄的机制，已成为生物多样性保护的核心议题。人为干扰正改变多种生态因子，但即便针对单一物种，这些因子的相对重要性如何随不同更新阶段发生变化，目前仍不明确。本研究以野外更新严重受限的孑遗物种水杉（Metasequoia glyptostroboides）为研究对象，依托54600粒种子开展控制实验，在其自然栖息地与邻近的未占据生境中探究幼苗出土与生长情况，以厘清种子可获得性、种间竞争以及草食/杂食动物取食在早期更新各阶段的作用。研究结果显示，上述因子主要在更新初始阶段发挥主导作用。相较于草食/杂食动物取食，种子可获得性与种间竞争是调控幼苗出土的关键因素。一年生幼苗存活率仅受种间竞争的显著影响，而二年生幼苗的存活则不受上述任一因子的影响。此外，我们在邻近未占据生境中检测到的因子影响效应与自然栖息地中相似，表明这些因子在限制种群扩张方面的作用。本研究结果可为推动水杉的自然更新与种群范围扩张提供参考建议，且本实验设计可应用于其他濒危植物的濒危原因评估。