Abstract
Nothofagus pumilio forests in Tierra del Fuego are the southernmost forests in the world, where extreme climate conditions represent a challenge to attain sustainable forest management. Retention forestry was proposed as an alternative to increase the species conservation in managed stands. Here, we synthetized results related to the implementation of a variable retention harvesting based on a combination of aggregate patches and dispersed retention during the last 18 years comparing with other silviculture proposals (e.g., shelterwood cuts) and control treatments (primary unmanaged forests). We summarized the results for (i) sawmill operations, (ii) timber yield, (iii) overstory stability, (iv) forest structure, (v) microclimate and natural cycles, (vi) natural regeneration dynamics (flowering, seeding, foraging, recruitment, growth, and mortality), and (vii) biodiversity (mammals, understory plants, mistletoes, birds, arthropods, mosses, lichens, and fungi). In general, aggregate patches maintained forest structure and micro-environmental variables, and slightly increased biodiversity and forest reproduction variables compared to unmanaged primary forests. On the contrary, dispersed retention decreased forest structure variables and greatly increased biodiversity (richness and abundance) when it was compared to unmanaged primary forests. Ecological conditions are influenced by variable retention harvesting, but direction and magnitude of the effect depend and differ according to retention types. Besides this, biodiversity taxa greatly differed among groups depending on retention types. In general, the species assemblages in aggregate patches were similar to those found in primary unmanaged forests, while they were significantly modified in the dispersed retention. This occurred due to (i) local extinction of some original species, (ii) the introduction of native species from the surrounding environments, or (iii) the invasion of exotic species. This silvicultural method has been a useful tool to conserve biodiversity and ecosystem functions, approaching to the balance between economy, ecology, and social requirements in the managed areas.
Highlights
The preservation of native forests should be one of the most important goals in forest management to preserve biodiversity and the multiple goods and ecosystem services that they provide (Kozlowski 2002; Perera et al 2018)
The impact was greater in the dispersed retention than in aggregate patches, which presented more similarities with primary unmanaged forests (81–95% of plant richness at baseline conditions was conserved in the harvested areas with variable retention)
Harvesting based on variable retention maintained enough vegetation structure in the managed stand to permit the establishment of early successional birds, and to maintain the bird species of primary unmanaged forests which could persist in the aggregate patches (Vergara and Schlatter 2006; Lencinas et al 2009, 2018)
Summary
The preservation of native forests should be one of the most important goals in forest management to preserve biodiversity and the multiple goods and ecosystem services that they provide (Kozlowski 2002; Perera et al 2018). The impact was greater in the dispersed retention than in aggregate patches, which presented more similarities with primary unmanaged forests (81–95% of plant richness at baseline conditions was conserved in the harvested areas with variable retention).
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