Jerônimo B. B. Sansevero

Ecological restoration success is higher for natural regeneration than for active restoration in tropical forests

Natural forest recovery is an effective ecological alternative to tree planting in tropical forests under certain conditions. Is active restoration the best approach to achieve ecological restoration success (the return to a reference condition, that is, old-growth forest) when compared to natural regeneration in tropical forests? Our meta-analysis of 133 studies demonstrated that natural regeneration surpasses active restoration in achieving tropical forest restoration success for all three biodiversity groups (plants, birds, and invertebrates) and five measures of vegetation structure (cover, density, litter, biomass, and height) tested. Restoration success for biodiversity and vegetation structure was 34 to 56% and 19 to 56% higher in natural regeneration than in active restoration systems, respectively, after controlling for key biotic and abiotic factors (forest cover, precipitation, time elapsed since restoration started, and past disturbance). Biodiversity responses were based primarily on ecological metrics of abundance and species richness (74%), both of which take far less time to achieve restoration success than similarity and composition. This finding challenges the widely held notion that natural forest regeneration has limited conservation value and that active restoration should be the default ecological restoration strategy. The proposition that active restoration achieves greater restoration success than natural regeneration may have arisen because previous comparisons lacked controls for biotic and abiotic factors; we also did not find any difference between active restoration and natural regeneration outcomes for vegetation structure when we did not control for these factors. Future policy priorities should align the identified patterns of biophysical and ecological conditions where each or both restoration approaches are more successful, cost-effective, and compatible with socioeconomic incentives for tropical forest restoration.

Twenty-Five Years of Restoration of an Igapó Forest in Central Amazonia, Brazil

This chapter describes a 25-year experience of restoration of a vast area impacted by a bauxite tailings spill over Lake Batata and its marginal igapo vegetation in Central Amazonia. It reviews papers and theses produced during this period and aims to provide a view of the restoration process from the past into the future. The main conclusions of this long-term restoration effort are: (1) Despite the sterility and difficult penetrability of the consolidated tailings substrate, igapo plants have been capable to establish and grow spontaneously in these areas, reaching reproductive stage and completing full life cycles; (2) Wherever natural regeneration was not possible, either due to topographic reasons or to water movements, human intervention by planting seedlings was also viable; (3) In areas subjected to longer term flooding (>8–9 months a year), planting is either physically not possible or, whenever possible, saplings die; (4) Natural regeneration and planting, altogether, were responsible for returning species richness and diversity to impacted areas, but floristic similarity with native, nonimpacted sites was moderate to low; this established vegetation produces shade, litter, organic matter and thus create new habitats and organic substrate for other species to establish naturally; (5) Recuperation is variable depending on site characteristics (annual length of flooding, species introduced, etc.) but often slow and in worse case scenarios new forests may take more than 75 years to converge to similarity with native nonimpacted igapo; thus, additional interventions are necessary to further forest growth, structure and diversity; (6) Despite the challenges posed by the scale of this enterprise, relevant actions to speed up successional trajectory are feasible, necessary and include continuous monitoring and evaluation, litter and seed addition, and selection of framework species for replacements.

Long-term regeneration of a tropical plant community after sand mining

Abstract Sandy coastal plant communities in tropical regions have been historically under strong anthropic pressure. In Brazil, these systems shelter communities with highly plastic plant species. However, the potential of these systems to regenerate without human assistance after disturbances has hardly been examined. We determined the natural regeneration of a coastal sandy plain vegetation (restinga) in Brazil, 16 years after the end of sand removal. We inventoried 38 plots: 20 within a sand‐mined site and 18 in an adjacent undisturbed site. We expected lower diversity values in the sand‐mined site compared to the undisturbed site, but similar species composition between the two sites due to the spatial proximity of the two sites and the high plasticity of restinga species. Species were ranked using abundance and importance value index in both sites, and comparisons were performed using Rényi entropy profiles, rarefaction curves, principal component analysis, and redundancy analysis. Species composition and dominant species differed markedly between the two sites. Bromeliads and Clusia hilariana, well‐known nurse plants, dominated the undisturbed site but were almost absent in the regenerating site. Species richness did not differ between both sites, but diversity was higher in the undisturbed site. Within‐site composition differences in the mined area were associated with field characteristics. Interestingly, species classified as subordinate or rare in the undisturbed site became dominants in the regenerating site. These newer dominants in the sand‐mined site are not those known as nurse plants in other restingas, thus yielding strong implications for restoration.

Secondary succession and fire disturbance promote dominance of a late-diverging tree lineage in a lowland Neotropical forest

Background: Variation in the distribution and abundance of woody plants as consequence of disturbances such as fire may be explained by lineage age. Aims: We tested whether lowland tropical tree lineages that colonise secondary forests are more late-diverging than clades from old-growth forests, and whether tree phylogenetic beta diversity from old-growth to secondary forests is higher in burned than non-burned secondary forests. Methods: We sampled tree communities in old-growth forests and in secondary forests with distinct disturbance histories (burned and unburned). We calculated mean family age in each plot, and tested for differences among forest types using ANOVA. A phylogenetic fuzzy-weighting procedure was employed to generate a matrix describing the abundance of tree clades per plot, which was then analysed using a principal coordinate analysis. Results: Most clades found in old-growth forests were underrepresented in secondary forests, which have been heavily colonised by a single species from a young lineage that is not found in old-growth forests. Phylogenetic beta diversity was higher between unburned secondary forests and old-growth forests than between burned secondary forests and old-growth forests. Conclusions: The capacity of Neotropical trees to colonise secondary forests and persist after fire disturbance may be related to the age of distinct lineages.