Forest restoration after alluvial gold mining can recover vegetation structure. A case study in Colombia

Technical reclamation and spontaneous succession (passive restoration) are the two main approaches for restoring post-mining sites worldwide. Despite substantial differences between both approaches, little is known regarding how they differ in terms of ecological outcomes. We assessed and compared the vegetation structure and composition in one spontaneous succession forest that is 29 years old, two technically reclaimed forests that are 2 and 10 years old after alluvial gold mining, and one old-growth reference forest in northeastern Antioquia, Colombia. We sampled trees and saplings establishing three Modified-Whittaker Plots in each site. We measured tree basal area, canopy cover, vegetation height, tree density, and species richness. Vegetation structure and composition differed considerably among restoration approaches. Species richness was significantly greater in the spontaneous succession forest than at the other sites. Similarly, technical reclamation significantly increased the vegetation attributes after 10 years, reaching values similar to the reference forest. We underscore the importance of fast-growth planted species (Acacia mangium, Samanea saman, and Schizolobium parahyba) to revegetate mining degraded lands.