Shade drives plant community changes of ground-layer savanna vegetation: Short-term changes under an experimental approach

Aim Woody-plant encroachment is a reality in many savannas worldwide, leading savannas to become replaced by forest ecosystems. As tree density and cover increase, increased shade and litter deposition may suppress the savanna's community of low-lying plants. By using field manipulation, we tested shading and litter effects, alone and in combination, on the savanna's ground-layer plant community. We investigated how changes in these environmental factors may affect the composition, structure, and above-ground biomass in the plant community of a species-rich Neotropical savanna. Location Savanna patches in the Cerrado, southeastern Brazil. Methods Annual surveys of the herbaceous-shrub layer in a three-year field manipulation experiment examining shading and litter deposition. Results Shade negatively affected all evaluated parameters, while litter addition had only minor effects. The largest losses of richness, density, and cover occurred in forbs and grasses. Increased shade resulted in a sharp decrease in the above-ground biomass of monocots. Conclusions Our results show that light is a strong environmental filter for the ground-layer community. The reductions in grass cover and biomass under shade treatments likely altered ecosystem functioning. Woody encroachment can thus be considered to represent a process that can alter the structure and functioning of savannas. Management interventions should therefore be taken to prevent woody encroachment or mitigate its harmful effects on savanna biodiversity and ecosystem functioning.

Automated summary

This study investigated the effects of shading and litter deposition on the ground-layer plant community in a Neotropical savanna. The results showed that shading had negative effects on all evaluated parameters, while litter addition had only minor effects. Increased shade resulted in a sharp decrease in the above-ground biomass of monocots. The study highlights the importance of light as an environmental filter and the potential impact of woody encroachment on savanna structure and functioning.