Abstract
Abstract Background Natural forests are intrinsically resilient to natural disturbances but can be vulnerable to anthropogenic impacts (e.g. wildfires and harvesting). Changes in natural dynamic pathways can modify the ecosystem structure and function, where legacies left after disturbances can play a major role in recovery. The objective was to characterize the resilience of different natural forest types in Tierra del Fuego, Argentina (Nothofagus pumilio, N. antarctica, and mixed) based on disturbance legacies and natural recovery of the forest structure after 60 years of anthropogenic impacts. Methods Study was conducted across a 300-ha landscape located in Tierra del Fuego (Argentina) where 130 stands were sampled, with forest structure, woody legacies and regeneration cover quantified. Generalized Least Squares models, indexes and Principal Component Analyses were used to compare forest types and determine thresholds in the recovery patterns after 60 years of the impacts (wildlife and harvesting). Results Forest structure values significantly decreased in impacted stands compared to non-impacted treatments. Some woody legacies increased after impacts (e.g. snags) while others tend to decrease (e.g. coarse-woody-debris). Regeneration cover generally decreased but it was associated with the impact type (e.g. wildfire was more aggressive than harvesting). The impact severity also modified the recovery values (wildfire > harvesting), where negative synergies were found in multivariate analyses. Some variables presented greater changes across the impact gradients, where some recovery thresholds can be identified and can be used to determine points of no return in forest recovery, e.g. Nothofagus pumilio was less resilient to the combination of impacts (wildfire and harvesting) than stands with N. antarctica trees. Conclusions Natural landscapes presented gradients in their forest structure from closed Nothofagus pumilio to open N. antarctica forests and grasslands. Human related impacts (e.g. wildfires and harvesting) significantly modified forest structure and legacies of the stands, which varied according to the type and magnitude of these impacts. Wildfire and harvesting generated negative synergies, being more severe in N. pumilio forests than in stands with N. antarctica trees. Indexes based on forest structure, legacies and regeneration values allow us to identify potential recovery thresholds related to human impacts after 60 years of the impacts (wildlife and harvesting). These findings can be allowed to design more efficient long-term monitoring to implement better adaptive management.