Accelerating Forest Succession in a Fragmented Landscape: The Role of Birds and Perches

Previous research suggests that in highly fragmented forest landscapes ecological succession can be arrested by lack of seeds, but that seed deposition abundance and diversity of bird-dispersed plants can be enhanced by bird-attracting structures such as snags. Consequently, bird perches remain a potential tool for accelerating ecological succession and reforesting disturbed land. Consequently, in order to determine the effectiveness of bird perches in reclaiming forested landscapes, seed dispersal, seedbank storage, and recruitment of bird-dispersed plants was studied on a central Florida mined site with clay-rich soil undergoing primary succession over a seven-year period. Data collection included 20 continuous months of seed dispersal data, an analysis of the total and germinable seedbanks, and plant recruitment at one and two years after a fire destroyed perches and burnt vegetation. Seed dispersal to perches reached a peak seedfall by weight in August, which was attributable to nonmigratory birds. Myrica cerifera, the most abundant species dispersed to the sites, was the only species dispersed during the winter and spring months, and it may be a keystone species for the frugivorous bird guild in central Florida. Seedfall beneath perches had a higher diversity of seed genera, and seed numbers (340 seeds m⁻² yr⁻¹) were 150 times greater than in sites without perches. Seeds of bird-dispersed plants in the seedbank under perches numbered 77 ± 33 (m⁻²) in total and 17 ± 5 for the viable seedbank. The population density of bird-dispersed plants was 1.4 and 2.0 plants m⁻² at one and two years afler the fire. Less than 0.06% of the dispersed seeds survived to become seedlings. Species composition shifted from seedfall to seedlings, with small-seeded, early-successional (r-selected) shrubs and herbs becoming relatively more common than the desired large-seeded, late-successional (K-selected) tree species. Perches attracted birds and associated seeds, but the physically harsh conditions created by primary succession and/or high predation on seeds appeared to reduce the success of the desired late-successional plant species. Nonetheless, there was a higher abundance and diversity of bird-dispersed plants under perches, suggesting that perch structures have a limited ability to enhance plant diversity under conditions of primary succession.