Abstract
BackgroundVariable retention (aggregated and dispersed retention) harvesting proposed for Nothofagus pumilio was designed for timber purposes and biodiversity conservation. Harvesting by opening canopy generates different microenvironments and creates contrasting conditions for seedling establishment, growth, and eco-physiology performance due to synergies (positives or negatives) with biotic and abiotic factors. This study evaluated the regeneration in different microenvironment conditions within managed stands during 5 years after harvesting. Remnant forest structure after harvesting and different microenvironments were characterized in managed stands, where 105 regeneration plots were measured (3 stands × 7 microenvironments × 5 replicas). We characterized the seedling bank, as well as growth and ecophysiology performance of the regeneration. Univariate and multivariate analyses were conducted for the comparisons.ResultsMicroenvironments offered different environmental conditions for natural regeneration (soil moisture and light availability). Seedling under debris and dicot plants showed better eco-physiological performance, establishment, and growth than plants growing under monocots or located in the dispersed retention without the protection of other understory plants. The most unfavorable microenvironment conditions were high canopy cover of remnant trees (inside the aggregates or close to trees in the dispersed retention) and heavily impacted areas (skidder extraction roads).ConclusionsFavorable microenvironments in the harvested areas will improve the natural recruitment, growth, and eco-physiology performance of the natural regeneration after harvesting. It is necessary to develop new silvicultural practices that decrease the unfavorable microenvironments (e.g., road density or excessive woody accumulation), to assure the success of the proposed silvicultural method.
Highlights
In the dispersed retention areas, 18.7 ± 1.7% of the surface was covered by debris, and 3.3 ± 2.2% was affected by skidder roads when timber logs were extracted, while retained live trees influence reaches to 6.1 ± 2.4% of the area
Basal area and leaf area index (LAI) were significantly higher inside the aggregates (77.5 m2 ha−1 and 1.85, respectively) than in the treatments located in the dispersed retention (12.2–19.0 m2 ha−1 and 0.33–0.68, respectively)
Active radiation above and below understory plants and debris changed according to the treatments, where greater differences between above and below were found under RT (37.9%) > DICO (27.7%) > MONO (20.5%) > DR (16%) > D (15.8%) > R (10%) > AR (Table 1)
Summary
The rationale of the silvicultural practices is based on the natural forest gap dynamics, where seedling establishment, growth, and yield are enhanced (Messier et al 1999; Caldentey et al 2009; Promis et al 2010) In these forests, abundant seedling establishment occurs after harvesting mainly from pre-existing regeneration (Gea et al 2004). The canopy opening determines a significant increase of the effective rainfall that reaches to the soil, increasing the moisture levels that can limit the seedling performance (Promis et al 2010; Martínez Pastur et al 2011b; Dreiss and Volin 2013) Both factors (moisture and light availability) can explain most of the establishment, growth, and eco-physiological performance of the seedlings (Rey et al 2004; Lencinas et al 2007; Martínez Pastur et al 2007a, 2014; Peri et al 2009; Soler et al 2011; Henn et al 2014).
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