Applicability of monitoring protocols developed for active restoration projects in the evaluation of passive restoration of a subtropical riparian forest in Brazil

Abstract

Current restoration monitoring protocols have been developed for active restoration projects (based on planting seedlings) and little is known about their applicability in assessing vegetation resulting from passive restoration, an important knowledge gap for the restoration of tropical and subtropical forests. The present study was developed in a 12-year-old subtropical riparian forest undergoing passive restoration (based on spontaneous natural regeneration), and aimed to evaluate the regenerating vegetation using two monitoring protocols developed for active ecological restoration. The following indicators of restoration success were evaluated: canopy cover; basal area; above-ground biomass; total richness; richness and density of regenerating trees. Passive restoration strategy has been found to be successful in the study area as the observed values for the indicators (except basal area and biomass) were above reference values specified for a 12-year-old active restoration. Our results also show that for most of the indicators of restoration success, the reference values established for the evaluation of active restoration projects may be surpassed through unassisted natural regeneration, suggesting the feasibility of the application of these monitoring protocols for the evaluation of passive restoration projects.