Restoration of riparian ecosystems posterior to tin mining in the Central Amazon: Restoration indicators and selection of suitable species for planting

Abstract

Riparian forests are fundamental for water and soil protection and favor the creation of gene flow corridors between forest remnants. The restoration of riparian forests by seedling planting can usually accelerate the succession process, but these ecosystems are seldom evaluated in post-mined areas in the Amazon. In this context, the objective of this study was to evaluate the restoration trajectory of riparian forests after tin mining, using composition and structure indicators along with the selectin of the most suitable species for planting according to height and DBH increments. A total of eight riparian forests of different planting ages (2014, 2015, 2016, 2017, and 2021/2022) were evaluated, being currently 8.5 (RF_8.5), 7.5 (RF_7.5), 6.5 (RF_6.5), 5.5 (RF_5.5) and ≤ 1.5 (RF_1.5) years old. Permanent plots of 30 m × 30 m were allocated in each forest, with the number of units varying according to the total area size, with a minimum of 3 plots allocated. Our results show a gradual increase in the density of individuals and species over the three evaluations performed, emphasizing RF_6.5 and RF_1.5 areas. Using the NMDS analysis, the RF_8.5 and RF_1.5 did not present any floristic-structural similarities. The 10 species with the highest IVI represented more than 60% of the total in all the restored ecosystems. V. guianenses presented the highest relative density for all ecosystems under restoration, except for RF_1.5, which S. alata was highlighted. P. pendula was the most suitable for planting in all assessed riparian forests when mortality and height and diameter increments were taken into consideration. Species with bioeconomic potential, such as C. guianensis, H. courbaril, E. precatoria and M. flexuosa, were also classified as efficient and considered structuring species.