Early response of Nothofagus antarctica forests to thinning intensity in northern Patagonia

Abstract

Nothofagus antarctica (G. Forst.) Oerst. stands of northern Patagonia (Argentina) have great potential to provide multiple ecosystem services. Nonetheless, the lack of basic information limits the application of silvicultural treatments to this forest type. This study reports the early response to three systematic strip thinning treatments (30, 50, and 70%) carried out during 2013 in a 30-year N. antarctica stand, where control plots (i.e. no thinning) were also established. Subplots were located within each plot. Basal diameters (BD) of all retained stems were measured in the non-vegetative season (winter) of 2016, 2017 and 2018, to calculate basal diameter annual increment (BDI), and stand volume growth. BDI ranged from 1.9 mm year-1 in the control plots to 2.7 mm year-1 at 70% thinning. Relative BDI also responded positively to thinning intensity. Stand volume growth decreased non-linearly with thinning intensity, from 3.36 m3 ha-1 year-1 in the control plots, and 0.71 m3 ha-1 year-1 when thinning was 70%. Smaller differences were observed between control plots, 30% thinning and 50% thinning. Our results show that Nothofagus antarctica forests, in the stem exclusion stage, respond to strip thinning. Thus, silviculture based on this management system could favor the development of retained trees without losing productivity if it remains under 50% intensity. This outcome represents an important incremental contribution to the design of silvicultural interventions in northern Patagonia.

Forest stand dynamics of a short‐stature tree species: Ecological knowledge for sustainable forest management

“…high elevation, high latitudes, or edaphic suboptimal sites) or at more favourable sites with periodic disturbances that vary in magnitude (Veblen, Donoso, et al., 1996). The synthesized knowledge from this theory has helped develop some silvicultural strategies in several Nothofagus ‐dominated forests in south central Chile and southern Argentina (Donoso et al., 2019; Gea‐Izquierdo et al., 2004; Goldenberg et al., 2021; Martínez Pastur et al., 2000, 2009; Reque et al., 2007; Soto et al., 2017, 2019). The major management implications of putting into practice the regeneration dynamics model of Nothofagus are the elaboration of thinning charts for vigorous second‐growth forests, mainly in N. dombeyi , N. obliqua and N. alpina (Chauchard et al., 2001; Gezan et al., 2007); the application of regeneration treatments like seed tree (Rosenfeld et al., 2006) and shelterwood (Donoso et al., 2022; Martínez Pastur et al., 2000); and selection harvesting in N. pumilio (Donoso et al., 2022; Gea‐Izquierdo et al., 2004; Soto et al., 2022).…”

Microclimatic Conditions Restrict the Radial Growth of Nothofagus antarctica Regeneration Based on the Type of Forest Environment in Tierra del Fuego

“…Nothofagus antarctica forests concentrate the cattle breeding of Tierra del Fuego, which is the main income source of ranching activities [2]. This management proposal simplifies the forest structure by opening the canopy through thinning, maintaining homogeneous tree and age distributions [4], and promoting an increase in understory biomass [5,6] for livestock production [7,8]. Forest structure values (e.g., volume, growth, and forest regeneration) have been previously studied [3,9], and several constraints during the management cycle may affect the natural regeneration of stands [8,10].…”

“…The main variables that influence regeneration performance are the microclimate (e.g., light and water availability) regulated by the forest overstory cover [12] and other biotic factors such as animal browsing (e.g., natural populations of Lama guanicoe or domestic livestock) [8,13]. Furthermore, harvesting modifies the forest structure by altering ecosystem functions, microclimates, and natural cycles depending on cut intensity [3]; e.g., thinning stimulates seedling growth by modifying light availability and soil moisture, and the remaining canopy overstory acts as a seed source and mitigates microclimatic conditions inside the harvested stands [4,14].…”