Environmental variables influencing regeneration of Nothofagus pumilio in a system with combined aggregated and dispersed retention

Alternative silvicultural practices with variable retention to improve understory plant diversity conservation in southern Patagonian forests

“…During the last 10 years, the variable retention approach has been proposed as a new and more conservative harvesting alternative for these forests (Martí-nez Pastur and Lencinas et al, 2007;Martínez Pastur et al, 2009). It has been found to mostly conserve microclimatic and heterogeneity characteristics of the original forest structure (Martínez Pastur et al, 2010), while aggregated retention benefits birds ) and moss conservation (Lencinas et al, 2008a). The variable retention silvicultural system is best suited for Appendix Table C Mean occurrence frequency of understory plant species at the baseline and during the first 4 years after harvesting in Nothofagus pumilio forests (DR = dispersed retention; AR = aggregated retention; ARI = aggregated retention inside aggregates; ARO = aggregated retention outside aggregates).…”

“…However, understory plant species have heterogeneous abundance and distribution patterns, which depends on the overstory species and structure (e.g., site quality of the stands or gap presence) (e.g., Warner and Harper, 1972;Veblen et al, 1977Veblen et al, , 1979Goldblum, 1997;Hutchinson et al, 1999;Damascos and Rapoport, 2002;Small and McCarthy, 2005;Fahey and Puettmann, 2008), as well as of micro-environmental and stand conditions (e.g., Huebner et al, 1995;Thomas et al, 1999;Palmer et al, 2000;Fraterrigo et al, 2009). Natural and anthropogenic disturbances in forest ecosystems affect these conditioning factors and modify understory diversity and distribution (Chen et al, 1993;Ohlson et al, 1997;Jenkins and Parker, 1999;Økland, 2000;Martínez Pastur et al, 2010). Therefore, herbaceous vegetation could act as a useful indicator of forest sustainability, ecosystem health and conservation status Lindenmayer et al, 2000;Dale et al, 2002).…”

“…However, there is a lack of information about the effectiveness of variable retention practices to improve understory vascular plant diversity conservation in southern Patagonian forests (Lencinas et al, 2008a). Also, few studies include medium-and long-term research to assess variable retention effects (Arnott and Beese, 1997;Hickey et al, 2001;Spence et al, 2002;Aubry et al, 2004;Martínez Pastur et al, 2010) or compare diversity structure before and after harvesting (Before-After-Control-Impact or BACI approach) as a way to determine the extent of variation in biodiversity prior to the implementation of silvicultural treatments (Vanha-Majamaa and Jalonen, 2001;Nelson and Halpern, 2005;Smith et al, 2008). Consequently, the objectives of this work were: (i) to define a baseline of understory plant diversity (cover, biomass and richness) in oldgrowth southern Patagonian Nothofagus pumilio forests (Argentina) comparing the influence of site quality and canopy gaps; (ii) to evaluate understory plant diversity conservation in variable retention harvested stands, compared to old-growth forests; and (iii) to assess temporal changes over a four-year time period after harvesting in harvested and old-growth stands.…”

Suitable conditions for natural regeneration in variable retention harvesting of southern Patagonian Nothofagus pumilio forests

“…Harvesting creates new microenvironments by generating large amounts of woody debris, which can potentially improve the eco-physiological response and the growth of seedlings compared with less shelter conditions (Martínez Pastur et al 2012. 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 2007aPeri et al 2009;Soler et al 2011;Henn et al 2014).…”

“…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 2007aPeri et al 2009;Soler et al 2011;Henn et al 2014). However, negative synergies have been observed in some microenvironments, where large canopy openings can produce drying effects, acting as a limiting factor for regeneration (McIntire et al 2016;Toro Manríquez et al 2018), as well as higher radiation levels that can increase the evaporation rates (Martínez Pastur et al 2011a, 2011b.…”