Temporal monitoring of ecological restoration by applied nucleation: A case study in the Pampa, southern Brazil

Abstract

Temporal monitoring of ecological restoration projects in the Pampa biome is still inadequate, with a gap in the knowledge of the successional trajectory of riparian forests under active restoration. Thus, monitoring of these areas based on a set of ecological indicators is crucial to assess the effectiveness of the restoration, as well as to ascertain the current state of the restoration project and the need for adaptive management actions. In this study, the progression of the techniques of planting in nuclei and passive restoration was investigated using ecological indicators. The study was carried out in the Serra do Sudeste, in an area of riparian forest. The region belongs to the Pampa biome, southern Brazil. The evaluations took place in two different monitoring periods, the first in 2018 and the second in 2021, in two areas, one under restoration by applied nucleation and the other under passive restoration. Ecological indicators of composition, structure, and function were measured, sampled in 10 plots through monitoring per area. The results showed significant differences between the monitoring periods in each area by the Kruskal-Wallis test (p < 0.05). The areas presented differences in floristic composition between monitoring periods by non-metric scaling analysis (nMDS), and differences in species contribution by similarity percentage analysis (SIMPER). The dendrometric variables (height, diameter, breast height, nuclei area, and crown area) presented a significant difference by the Kruskal-Wallis test (p < 0.05) in the evaluation of the development of the nuclei. The ecological indicators of structure (canopy cover, soil cover by litter and trees) and functionality (biotic dispersal syndrome) were statistically higher in the second monitoring period in the area under restoration by applied nucleation. In the area under passive restoration, the indicators of structure (litter thickness and soil cover by litter and trees) and functionality (biotic dispersal syndrome) were also statistically higher in the second monitoring period. In both areas, Baccharis dracunculifolia DC. was the species that most contributed to the floristic dissimilarity between the monitoring moments. In the development of the nuclei, the dendrometric variables were statistically superior in the second monitoring period, pointing to progression in the development of the nuclei. It is concluded that the restoration technique by applied nucleation is effective in the studied area, as the nuclei progress over time. The area under passive restoration showed signs of changes in ecological succession. The study result provide support for the improvement in future restoration projects for riparian areas in the Pampa biome.