Prolonged duration of seedling recruitment in an invasive species mediated by aerial seed banks

Abstract

Seed dormancy and dispersal time determine recruitment windows, yet their interaction in species with aerial seed banks is poorly understood. We employed Leucaena leucocephala, an invasive legume with physical dormancy (PY) and both aerial seed bank (serotiny) and soil seed banks, to investigate whether canopy retention influences PY release and to compare the persistence and their contributions in inhabitation. We combined canopy and soil seedbank monitoring, germination assays, and long-term tracking of seed bank dynamics from seed maturation to depletion in a subtropical monsoon forest. Our results show that seed lens gradually become water permeable under warm and humid treatments, leading to PY release. With delayed dispersal and canopy retention, the proportion of PY seeds declined gradually. Seeds remained in the canopy for up to 10 months, through to the following summer, during which their water permeability and dormancy release increased progressively. In contrast, soil seed banks were depleted within 5 days of post-rain dispersal under natural conditions due to rapid germination and predation, whereas artificial soil seed banks established with freshly matured seeds under predator-exclusion conditions also persisted until the following summer. PY release in both banks peaked in spring, synchronizing germination with seasonal rains. The temporal asynchrony in PY release and serotiny partitions seed depletion, minimizing predation risk, and synchronizing germination with seasonal rains, thereby promoting establishment and sustaining the invasion species L. leucocephala.