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.

Early Bird Assemblages under Different Subtropical Forest Restoration Strategies in Brazil: Passive, Nucleation and High Diversity Plantation

“…It is important to emphasize that in the dynamics of colonization, in some situations the bird assemblage converges rapidly to a structure similar to that of nearby forest fragments [65]. On other occasions the structure of the avian fauna may take different directions, with species adapted to the structure of the vegetation [12,66], generally influenced by the distance between forest fragments or by the change in the structure of the vegetation [23,67].…”

International principles and standards for the practice of ecological restoration. Second edition

“…by mimicking natural disturbances or by providing key resources). Examples of abiotic interventions include: actively remediating substrate chemical or physical conditions; building habitat features such as shellfish reefs (O'Beirn et al ); reshaping watercourses (Jordan & Arrington ) and landforms (Prach & Hobbs ); reinstating environmental flows and fish passage in estuaries and rivers (Kareiva et al ); applying artificial disturbances to break seed dormancy (Mitchell et al ); and, installing habitat features such as hollow logs, rocks, woody debris piles, soil microniches, and perch trees (Elgar et al ; Castillo‐Escrivà et al ). Examples of biotic interventions include: controlling invasive species (Saunders & Norton ; Chazdon et al ); supplementary reintroduction of species that cannot migrate into the restoration area without assistance (e.g.…”

Efeito de Herbicidas sobre a Biota de Invertebrados do Solo em Área de Restauração Florestal

“…Entre esses, a competição das gramíneas com as mudas florestais por recursos-chave como água, luz e nutrientes (Victoria Filho, 1987;Machado et al, 2013) requer intervenções que eliminem a presença delas, facilitando ou mesmo propiciando o reestabelecimento da vegetação florestal (Elgar et al, 2014).…”