title: Overcoming barriers to seedling regeneration during forest restoration on tropical pasture land and the potential value of woody weeds.
abstract: Combating the legacy of deforestation on tropical biodiversity requires the conversion to forest of large areas of established pasture, where barriers to native plant regeneration include competition with pasture grasses and poor propagule supply (seed availability). In addition, initial woody plants that colonise pasture are often invasive, non-native species whose ecological roles and management in the context of forest regeneration are contested. In a restoration experiment at two 0.64 ha sites we quantified the response of native woody vegetation recruitment to (1) release from competition with introduced pasture grasses, and (2) local facilitation of frugivore-assisted seed dispersal provided by scattered woody plants and artificial bird perches. Herbicide pasture grass suppression during 20 months caused a significant but modest increase in density of native woody seedlings, together with abundant co-recruitment of the prominent non-native pioneer wild tobacco (Solanum mauritianum). Recruitment of native species was further enhanced by local structure in herbicide-treated areas, being consistently greater under live trees and dead non-native shrubs (herbicide-treated) than in open areas, and intermediate under bird perches. Native seedling recruitment comprised 28 species across 0.25 ha sampled but was dominated by two rainforest pioneers (Homalanthus novoguineensis, Polyscias murrayi). These early results are consistent with the expected increase in woody vegetation recruitment in response to release from competitive and dispersive barriers to rainforest regeneration. The findings highlight the need for a pragmatic consideration of the ecological roles of woody weeds and the potential roles of "new forests" more broadly in accelerating succession of humid tropical forest across large areas of retired agricultural land.
authors.affiliation: School of Environment, Environmental Futures Research Institute, Griffith University Brisbane, QLD, Australia.
authors.forename: Amelia T
authors.initials: AT
authors.lastname: Elgar
authors.affiliation: School of Environment, Environmental Futures Research Institute, Griffith University Brisbane, QLD, Australia ; Tablelands Community Revegetation Unit Malanda, QLD, Australia.
authors.forename: Kylie
authors.initials: K
authors.lastname: Freebody
authors.affiliation: Centre for Rainforest Studies, The School for Field Studies Yungaburra, QLD, Australia.
authors.forename: Catherine L
authors.initials: CL
authors.lastname: Pohlman
authors.affiliation: School of Biological Sciences, The University of Queensland St Lucia, QLD, Australia.
authors.forename: Luke P
authors.initials: LP
authors.lastname: Shoo
authors.affiliation: School of Environment, Environmental Futures Research Institute, Griffith University Brisbane, QLD, Australia.
authors.forename: Carla P
authors.initials: CP
authors.lastname: Catterall
keywords: novel ecosystem; old field; plant invasion; rainforest; regrowth; seed dispersal