Direct seeding of 16 Brazilian savanna trees: responses to seed burial, mulching and an invasive grass

Aims: To address whether seed and seedling functional traits have a significant effect on germination rates and seedling survival in direct-seeding restoration efforts. We tested the hypotheses that: (1) seed burial only favours the emergence of round seeds; and (2) straw mulching improves soil moisture and prevents the emergence of the invasive grass Urochloa decumbens, promoting the establishment of native tree seedlings. Location: Experimental field, Central Brazil. Savanna, recently dominated by exotic pasture. Methods: We evaluated the effects of seed burial (surface and buried) and mulching (no-mulch, 5-cm straw mulch and 10-cm straw mulch) on the emergence, survival and growth of 16 species of native Cerrado tree species with variable seed sizes and shapes and seedling types. Thirty seeds of each species were sown per treatment combination in three blocks. Results: Seed burial did not affect the emergence of species with round seeds, but negatively affected species with flat seeds and phanerocotylar–epigeal–foliaceous seedlings. Straw mulching reduced the emergence of flat seeds and phanerocotylar seedlings, but increased soil moisture and strongly reduced U. decumbens emergence, resulting in a higher growth rate of tree seedlings up to 1 yr for five species. Conclusion: Direct seeding is an effective technique to plant a mixture of Cerrado tree species for restoration, provided the soil is well prepared and there are mechanisms to control invasive species.