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

Abstract

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.

Abandoned pastures cannot spontaneously recover the attributes of old‐growth savannas

“…In the last 10 years, practically all countries in the world have made ambitious global commitments involving the restoration of degraded ecosystems (Aronson & Alexander, ; Suding et al., ), including Neotropical savannas (Strassburg et al., ), which are biodiversity hotspots (Myers, Mittermeier, Mittermeier, Da Fonseca, & Kent, ). Therefore, restoration scientists and practitioners have developed and tested several methods to actively restore these ecosystems (Ferreira, Walter, & Vieira, ; Pereira, Laura, & Souza, ; Pilon, Buisson, & Durigan, ; Silva, Oliveira, Rocha, & Vieira, ; Silva & Vieira, ). However, active savanna restoration is challenging due to the high cost of controlling exotic grasses (Breed, Lowe, & Mortimer, ) and the unavailability of commercial propagules (vegetative material or seeds) of native plants, especially grasses, forbs and shrubs, to replace exotics (Pilon et al., ).…”

Effects of initial functional‐group composition on assembly trajectory in savanna restoration

“…Some examples are cerrado savannas in Brazil (Pellizzaro et al., ;Pilon et al., ; Silva, Oliveira, da Rocha, & Vieira, ), semi‐natural grasslands in Europe (Baasch, Engst, Schmiede, May, & Tischew, ; Hedberg & Kotowski, ), grasslands in USA (Holl et al., ; Martin, Moloney, & Wilsey, ), African savannas (Kinyua, McGeoch, Georgiadis, & Young, ) and Australian savannas (O'Dwyer & Attiwill, ). There is evidence that it is possible to reintroduce many native species of trees and some shrubs and herbs in the Brazilian savanna through direct seeding (Pellizzaro et al., ; Silva & Vieira, ). However, the present study shows that there are major challenges to establishing an initial community resistant to re‐establishment of invasive grasses.…”

“…Tachigali vulgaris is a fast‐growing tree, and this ability allowed this species to overcome the grass cover. All other 21 seeded trees had good establishment, but a very slow growth rate (Pellizzaro et al., ; Silva & Vieira, ). Not only did Schizachyrium sanguineum occupy the spaces left by the short life‐cycle species, but it was also able to invade plots dominated by invasive grasses.…”

“…Direct seeding, hay transfer and topsoil transfer are considered effective methods for grassland restoration (Ferreira et al., ; Hedberg & Kotowski, ; Pilon, Buisson, & Durigan, ). There are few studies on savanna restoration, but direct seeding is the most commonly used technique (Palma & Laurance, ) and has been successfully used to establish native species in Brazilian savannas (Pellizzaro et al., ; Silva & Vieira, ). The advantages of this method include low cost and easy implementation (Grossnickle & Ivetić, ; Palma & Laurance, ).…”

Tailoring restoration interventions to the grassland‐savanna‐forest complex in central Brazil

“…Fertilizers and agricultural limestone are commonly added to enrich soil and neutralize acidity, frequently favoring invasions by exotic grasses (Bustamante et al ). Pastures are typically seeded with highly competitive exotic grass species, which rapidly spread into agricultural fields and degraded areas, increasing fire frequency (Pivello et al ), outcompeting native species, and decreasing the resilience of the herbaceous layer (Cava et al ; Silva & Vieira ; Coutinho et al ).…”