118
The two species conform an altitudinal ecological gradient along their natural
distribution, with N. pumilio dominating at higher elevations and N. antarctica at
lower sites. Nothofagus pumilio usually forms large masses of pure stands associated with climax forests (late-successional species) but also in co-dominance with
Nothofagus betuloides (in the south) or Araucaria araucana (in the north). Individual
trees can be taller than 35 m (Tortorelli 1956) (Fig. 5.1a) and grow in environments
with deep, well-drained soils; while reaching the timberline, they tolerate low temperatures and frosts as a shrub. On the other hand, N. antarctica is the species with
the widest ecological plasticity and phenotypic variation (Ramírez et al. 1997)
among their South American congeners. It occurs in cold humid valleys with heavy
clay soils, in peat bogs, and in rocky and xeric sites like the Patagonian steppe,
forming monospecific masses of shrubs or small trees (Fig. 5.1b).
Nothofagus antarctica is considered a pioneer and resprouting species and has a
great capacity for clonal reproduction (Premoli and Steinke 2008), while N. pumilio
can only reproduce generatively. Clonal reproduction in ñire is suggested as an
adaptation to recurrent disturbances, among which fires are the most common in
the region.
Both are related species included in the subgenus Nothofagus, one of the four
defined within the Nothofagaceae family (Hill and Jordan 1993). Phylogenetic analyses, including morphology, conserved DNA sequences, and fossils, agreed in a
common ancestor among Nothofagus betuloides and N. pumilio/N. antarctica sister
species (Manos 1997; Sauquet et al. 2012). Recently, it has been suggested that
N. pumilio would be the ancestral species within the subgenus (Acosta and Premoli
2010). Extant species included in the clade shared the pollen type, nominated equivalently as “N. fusca Type b” (Manos 1997) or “dombeyi” (Villagrán et al. 1995;
Heusser et al. 1999) all of them are cold-tolerant species.
As deciduous species, their dormant buds during winter determine a growing
season restricted to spring and summer, whose length varies depending on available
resources; particularly drought stress during summer is among the most critical factors. Pollen and seed dispersion is mediated by wind. Most commonly, seeds reach
short distances from the mother tree (Rusch 1993). Seed production is not regular
over consecutive seasons, being years of greater production associated with greater
germination power and viability (masting) (Donoso 1993). Variability in seed production and seed quality was suggested to be linked to stand conditions, e.g., secondary N. antarctica forests have been observed at 51° S to have better seed quality
(Soler Esteban et al. 2010), and also differences have been reported between pure
and mixed N. pumilio forests (Toro Manríquez et al. 2016). Moreover, in these species, seeds have a stage of reduced viability and do not form persistent seed banks
(Cuevas and Arroyo 1999). Seedling recruitment and survival are crucial stages for
regeneration, varying in number of established individuals year after year, being
tightly linked to the microclimate conditions within natural forests (e.g., Soler et al.
2013; Bahamonde et al. 2018). Regeneration dynamics is the result of large-scale
disturbances, which cause the replacement of complete stands (e.g. mass removal
on steep slopes), or small-scale disturbances, mainly the gap dynamics, which
C. Soliani et al.
The two species conform an altitudinal ecological gradient along their natural
distribution, with N. pumilio dominating at higher elevations and N. antarctica at
lower sites. Nothofagus pumilio usually forms large masses of pure stands associated with climax forests (late-successional species) but also in co-dominance with
Nothofagus betuloides (in the south) or Araucaria araucana (in the north). Individual
trees can be taller than 35 m (Tortorelli 1956) (Fig. 5.1a) and grow in environments
with deep, well-drained soils; while reaching the timberline, they tolerate low temperatures and frosts as a shrub. On the other hand, N. antarctica is the species with
the widest ecological plasticity and phenotypic variation (Ramírez et al. 1997)
among their South American congeners. It occurs in cold humid valleys with heavy
clay soils, in peat bogs, and in rocky and xeric sites like the Patagonian steppe,
forming monospecific masses of shrubs or small trees (Fig. 5.1b).
Nothofagus antarctica is considered a pioneer and resprouting species and has a
great capacity for clonal reproduction (Premoli and Steinke 2008), while N. pumilio
can only reproduce generatively. Clonal reproduction in ñire is suggested as an
adaptation to recurrent disturbances, among which fires are the most common in
the region.
Both are related species included in the subgenus Nothofagus, one of the four
defined within the Nothofagaceae family (Hill and Jordan 1993). Phylogenetic analyses, including morphology, conserved DNA sequences, and fossils, agreed in a
common ancestor among Nothofagus betuloides and N. pumilio/N. antarctica sister
species (Manos 1997; Sauquet et al. 2012). Recently, it has been suggested that
N. pumilio would be the ancestral species within the subgenus (Acosta and Premoli
2010). Extant species included in the clade shared the pollen type, nominated equivalently as “N. fusca Type b” (Manos 1997) or “dombeyi” (Villagrán et al. 1995;
Heusser et al. 1999) all of them are cold-tolerant species.
As deciduous species, their dormant buds during winter determine a growing
season restricted to spring and summer, whose length varies depending on available
resources; particularly drought stress during summer is among the most critical factors. Pollen and seed dispersion is mediated by wind. Most commonly, seeds reach
short distances from the mother tree (Rusch 1993). Seed production is not regular
over consecutive seasons, being years of greater production associated with greater
germination power and viability (masting) (Donoso 1993). Variability in seed production and seed quality was suggested to be linked to stand conditions, e.g., secondary N. antarctica forests have been observed at 51° S to have better seed quality
(Soler Esteban et al. 2010), and also differences have been reported between pure
and mixed N. pumilio forests (Toro Manríquez et al. 2016). Moreover, in these species, seeds have a stage of reduced viability and do not form persistent seed banks
(Cuevas and Arroyo 1999). Seedling recruitment and survival are crucial stages for
regeneration, varying in number of established individuals year after year, being
tightly linked to the microclimate conditions within natural forests (e.g., Soler et al.
2013; Bahamonde et al. 2018). Regeneration dynamics is the result of large-scale
disturbances, which cause the replacement of complete stands (e.g. mass removal
on steep slopes), or small-scale disturbances, mainly the gap dynamics, which
C. Soliani et al.