Making the most of native seeds: Management techniques interact with seed and seedling traits for enhancing direct seeding success

Abstract

Direct seeding offers a cost-effective approach to large-scale restoration, but seedling establishment can vary greatly across species and regions. This study investigates how management techniques used for seed processing, site preparation, seeding, and post-seeding management interact with seed/seedling traits and influence direct seeding success. We conducted a systematic review of Brazilian direct seeding research, encompassing 26 % of global studies. We focused on paired experiments comparing management techniques against control treatments to analyze seedling establishment rates for trees, shrubs, and palms. The techniques included pre-soaking seeds, overcoming seed dormancy, seed burial, mulch application, soil fertilization, intercropping with green manure or agricultural crops, weed control, and sowing in the shade of secondary vegetation. Seed traits were fresh mass, water content, and shape, and seedling traits were functional morphology, successional guild, and vegetation guild, i.e., forest or savanna. Pre-germination treatments offered no significant benefit. Seed burial doubled establishment, and mulch application only aided unburied seeds. Organic fertilization reduced establishment for savanna species, while intercropping with green manure or crops enhanced establishment for forest species. Weed control effectiveness depended on functional traits. Mowing favored pioneers, while hoeing or herbicide application benefited large-seeded and epigeal-foliaceous-cotyledon seedlings. Pioneer species establishment was 15 % in full sun and 3 % in the shade, while shade-tolerant climax species established at 8 % in full sun and 28 % in the shade. By implementing management techniques, direct seeding success can be increased up to fourfold. This translates to a potential reduction in seed usage, the primary cost of direct seeding, by 25–75 %. These findings pave the way for cost-effective restoration efforts with improved seedling establishment rates.