Influence of environmental conditions and initial sapling size in Nothofagus survival and growth: Implications for restoration of burnt sub‐Antarctic forests

Abstract

The sub-Antarctic forests in Tierra del Fuego mountains are considered one of the few remaining wilderness areas on the planet; however, human disturbances like wildfires, exotic species, and so forth exacerbate their degradation. In 2012, a human-caused wildfire started in a remote forest-mountain area, and 2 years after that, a reforestation project began to restore the natural canopy layer. Saplings of the native Nothofagus trees were obtained through the bare root method from undisturbed areas. In this study, we evaluated the influence of (1) macro- (considering natural topography and vegetation physiognomy) and micro-environments (topography, canopy cover, substrate, and understory cover) affected by fire; and (2) the extraction size of the saplings (initial size), on survival and growth of planted saplings, over 5 years. Total sapling survival was 41.4% with a mean growth rate of 8.46 cm year−1. Survival and growth were influenced by the studied variables. At a macro-environment level, tree saplings showed higher success in well-drained zones, meanwhile at the micro-environment level saplings performed better in those that contribute to retain soil moisture and avoiding evapotranspiration. We conclude that environmental features influence differentially depending on the scale of analysis. To restore burnt temperate forests applying the bare root method, we recommended using Nothofagus saplings <40 cm tall for better results. In this sense, we demonstrated the effectiveness of the method since comparable results were obtained in other restoration experiences. This method can also be applied in areas without nursery material, when the biology of tagged plants was appropriated, for example shallow growth of root systems, formation of natural tree seedling banks. This work represents one of the few medium-term restoration experiences reported for the southernmost forests of the planet: our findings could be applied in other reforestation experiences, making noticeable improvements in the recovery process.