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

Abstract

Aims:Indicators that can provide information during the early stages of restoration are very useful for predicting restoration outcomes. We posed the following questions: Can savanna restoration outcomes be affected by the initial functional-group composition? Are there functional groups that, when established early, can prevent colonization by invasive grasses, trigger a successful restoration trajectory, and be used as early indicators of restoration success? Methods:We established 110 plots spanning a naturally occurring range of species composition in savanna areas that had been restored through direct seeding. We looked for different initial compositions of the following functional groups: perennial grasses, annual grasses, short-lived shrubs, and invasive grasses. We measured vegetation cover over two years and evaluated the effects of the initial functional composition on the successional trajectory of the plots. Results:The initial dominant functional group determined the assembly trajectory.Short-lived and fast-growing species were replaced by perennial species, indicating a fast species turnover. Invasive grass cover remained stable over time, demonstrating that once they establish and dominate an area, an alternative stable state is achieved. Conclusions:Our results demonstrate the importance of introducing a mixture of functional groups when restoring savannas in severely disturbed areas. Fast-growing and short-lived species are important for quickly covering the ground, creating the conditions for the establishment of perennial grasses that naturally dominate the herbaceous layer of savannas. Trees are also characteristic of the savanna structure and must be introduced. Our results indicate that invasive grasses must be eliminated and/or constantly controlled before native species are introduced. K E Y W O R D Sassembly trajectory, cerrado, direct seeding, functional group, invasive grasses, priority effects, savanna restoration, species turnover, succession 62 |

Lessons on direct seeding to restore Neotropical savanna

“…Fertilizers and agricultural limestone are commonly added to enrich soil and neutralize acidity, frequently favoring invasions by exotic grasses (Bustamante et al 2012). 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 1999), outcompeting native species, and decreasing the resilience of the herbaceous layer (Cava et al 2017;Coutinho et al 2018).…”

“…1). Burning may also be useful when combined with mechanical and/or chemical control of invasive grasses (Martins et al 2011;Coutinho et al 2018). But most invasive grass species are from other fire-adapted systems so burning alone is unlikely to control these grasses (D'Antonio & Vitousek 1992).…”

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

“…Restoring the millions of hectares of degraded grasslands‐savanna‐forest mosaics in the Cerrado region and in other continents is a daunting task, particularly in open canopy ecosystems where invasive grasses pose a formidable obstacle to recovery (Coutinho et al ; Sampaio et al in review). This highlights the importance of slowing the rapid ongoing conversion rate of Cerrado (Klink & Machado ) and grassy biomes worldwide (Veldman et al ), as conserving old‐growth grassland and savanna ecosystems is the best option.…”

“…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 ).…”

“…1). Burning may also be useful when combined with mechanical and/or chemical control of invasive grasses (Martins et al 2011;Coutinho et al 2018). But most invasive grass species are from other fire-adapted systems so burning alone is unlikely to control these grasses (D'Antonio & Vitousek 1992).…”