Dispersal mode mediates the seed functional traits of woody plants’ responses to urbanization in remnant forest patches

Abstract

Urban remnant forests are essential for biodiversity conservation within city landscapes, facing direct impacts from urbanization and indirect changes from surrounding land use alterations that affect seed dispersal and plant diversity. This study focuses on the impacts of urbanization on woody plants in Guiyang, China, emphasizing seed functional traits to understand plant adaptive strategies and support urban biodiversity conservation. We surveyed woody plants across 120 plots in 15 remnant forest patches, examining five seed traits and their modes of dispersal. Results reveal that shrubs in such forests possess smaller seeds and lower yields, with a preponderance of seeds dispersed by birds rather than by wind or over short distances, unlike tree communities. Urbanization notably diminishes important seed traits like mass and length in trees, particularly for species with limited dispersal reach, while bird-dispersed species see an increase in quantity of seed but a reduction in seed mass. Meanwhile, seed yield rate in tree communities increased, but decreased in shrub communities. Structural equation modeling indicated that urbanization influences on seed traits are mediated by dispersal mechanisms and edge effects in trees, but only dispersal mechanisms in shrubs. The study concludes that the dispersal mode significantly mediates how seed functional traits of woody plants respond to urbanization in these forest remnants. Urban planning should therefore prioritize enhancing green corridors to facilitate natural seed dispersal and boost animal diversity, which could improve dispersal outcomes and contribute to maintaining and restoring plant diversity in urban forests.