494
The trends indicated by the models imply that the current mixed forests may
gradually be replaced by pure N. obliqua stands. The fact that recruitment at some
localities is already now largely dominated by saplings of N. obliqua (Sola et al.
2015; Sola et al. 2016) would be supporting the modeling results. However, this
might also be the legacy of past logging, which was more intense toward N. alpina
thus likely promoting this differential recruitment. Another important issue is natural interspecific hybridization. Hybrids close their growing season later, and under
the current climate they are more susceptible to early frosts (Crego 1999). In this
sense, they might be favored by a warming climate, if it implies a less frequent
occurrence of early frosts. A successional change toward a hybrid swarm might
already be occurring in the mixed forest and could as such increase the adaptive
potential of these populations (Rieseberg et al. 2003; Lexer et al. 2004; Becker
et al. 2013).
Example 2: Altitudinal Shifting of Neighboring Nothofagus Species
The elucidation of the physiological and molecular responses of trees to changes in
the environment becomes a priority in the context of the aforementioned global
climate change. Many works report physiological responses of woody species to
different environmental factors such as water and temperature. However, most of
these studies were performed under controlled conditions, and little is known about
the responses of trees to changes in the environment in the wild.
Environmental gradients can work as “natural laboratories” for the study of
growth and development of tree species in relation to the conditions they endure.
Particularly, altitudinal gradients constitute a useful tool to study the influence of
natural climatic conditions on the distribution of species (Körner 2000). Although
numerous environmental factors vary with altitude (Körner 2007), temperature is
the cue that is usually more correlated with elevation (Loarie et al. 2009), with a
drop of air temperature of 5 to 6.5 °C per 1000 m (Jump et al. 2009). The use of
these natural laboratories constitutes a promising approach to predict fitness of
woody plant species in contrasting sites and the adjustment of their ranges to a
changing environment. In this regard, we present here a case study in Northern
Patagonia with three Nothofagus species that grow separately along an altitudinal
gradient: N. obliqua at 650–850 m asl, N. alpina between 850 and 1000 m asl, and
N. pumilio above 1000 m asl. In these ecosystems, temperature is the environmental
factor that shows the strongest association with altitude.
The sharp separation of altitudinal habitats of these species suggests a clear preference for particular thermal environments. This can be tested combining laboratory
experiments, in which the particular effect of temperature can be evaluated under
controlled conditions, with experiments across different altitudes aiming to test species’ fitness inside and outside their natural distribution range. For this purpose, it is
necessary to identify the particular processes across the whole plant life cycle that
are susceptible to changes in the natural habitat and study their environmental regulation. It is known that germination and seedling establishment usually show a
strong environmental vulnerability (Grubb 1977; Bykova et al. 2012; Green et al.
2014); therefore they can be included among the potential candidate traits. In this
M. J. Pastorino et al.
The trends indicated by the models imply that the current mixed forests may
gradually be replaced by pure N. obliqua stands. The fact that recruitment at some
localities is already now largely dominated by saplings of N. obliqua (Sola et al.
2015; Sola et al. 2016) would be supporting the modeling results. However, this
might also be the legacy of past logging, which was more intense toward N. alpina
thus likely promoting this differential recruitment. Another important issue is natural interspecific hybridization. Hybrids close their growing season later, and under
the current climate they are more susceptible to early frosts (Crego 1999). In this
sense, they might be favored by a warming climate, if it implies a less frequent
occurrence of early frosts. A successional change toward a hybrid swarm might
already be occurring in the mixed forest and could as such increase the adaptive
potential of these populations (Rieseberg et al. 2003; Lexer et al. 2004; Becker
et al. 2013).
Example 2: Altitudinal Shifting of Neighboring Nothofagus Species
The elucidation of the physiological and molecular responses of trees to changes in
the environment becomes a priority in the context of the aforementioned global
climate change. Many works report physiological responses of woody species to
different environmental factors such as water and temperature. However, most of
these studies were performed under controlled conditions, and little is known about
the responses of trees to changes in the environment in the wild.
Environmental gradients can work as “natural laboratories” for the study of
growth and development of tree species in relation to the conditions they endure.
Particularly, altitudinal gradients constitute a useful tool to study the influence of
natural climatic conditions on the distribution of species (Körner 2000). Although
numerous environmental factors vary with altitude (Körner 2007), temperature is
the cue that is usually more correlated with elevation (Loarie et al. 2009), with a
drop of air temperature of 5 to 6.5 °C per 1000 m (Jump et al. 2009). The use of
these natural laboratories constitutes a promising approach to predict fitness of
woody plant species in contrasting sites and the adjustment of their ranges to a
changing environment. In this regard, we present here a case study in Northern
Patagonia with three Nothofagus species that grow separately along an altitudinal
gradient: N. obliqua at 650–850 m asl, N. alpina between 850 and 1000 m asl, and
N. pumilio above 1000 m asl. In these ecosystems, temperature is the environmental
factor that shows the strongest association with altitude.
The sharp separation of altitudinal habitats of these species suggests a clear preference for particular thermal environments. This can be tested combining laboratory
experiments, in which the particular effect of temperature can be evaluated under
controlled conditions, with experiments across different altitudes aiming to test species’ fitness inside and outside their natural distribution range. For this purpose, it is
necessary to identify the particular processes across the whole plant life cycle that
are susceptible to changes in the natural habitat and study their environmental regulation. It is known that germination and seedling establishment usually show a
strong environmental vulnerability (Grubb 1977; Bykova et al. 2012; Green et al.
2014); therefore they can be included among the potential candidate traits. In this
M. J. Pastorino et al.