Comparative study reveals management of a dominant invasive plant facilitates subtropical forest regeneration

Invasive plant species can drive ecosystem change, particularly on oceanic islands that are vulnerable to plant invasions and subsequent biodiversity loss. While invasive species management is vital for habitat restoration, efficacy of management efforts and the ability of native plants to regenerate varies among studies. The aim of this study was to examine the consequences of managing a thicket-forming woody plant species— Psidium cattleyanum Sabine (strawberry guava)—on subtropical forest regeneration, comparing spatial scales and management periods. We surveyed 15 locations on Norfolk Island, an isolated Pacific Island with a high proportion of endemic and threatened species, by establishing paired managed and unmanaged plots to assess changes in species-area relationships, abundance, richness, and composition of the plant community. Total plant richness was higher in managed plots at the largest scale examined (125 m 2 ). However, there was no significant difference between managed and unmanaged plots in the slopes of species-area relationships when canopy, understory, and seedling strata were combined. Stratum-specific analyses revealed that management-driven changes were most evident in the subcanopy strata, which had significantly higher woody plant abundance and richness in managed plots. Compositional dissimilarity between managed and unmanaged plots was greater in locations with higher moisture levels, suggesting that post-management regeneration is related to environmental conditions. This study suggests that P. cattleyanum suppresses plant recruitment and its removal allows for forest regeneration, indicating that management of dominant invasive woody species facilitates plant recruitment on Norfolk Island if nearby native propagule sources are present.