179
the Andes, with fires occurring firstly in Argentina. However, the active disturbance
period stopped sooner in Argentina due to an earlier implementation of protected
areas (Mundo et al. 2013).
The growth of A. araucana is controlled by climatic signals where tree diameter
increased in years with cool and wet springs and summers (Villalba et al. 1989;
Mundo et al. 2012; Muñoz et al. 2014). However, the response on diameter growth
due to climate variability induced by “La Niña” events and SAM conditions varied
among sex and tree age (Hadad 2014; Hadad et al. 2015). On female trees, the positive conditions for growth are necessary during previous and current year (so control by “La Niña” event in the previous year). However, on male trees, only cool
temperatures in the previous year and humid conditions during the current year
promote diameter growth (so control by SAM conditions during growth). On the
other hand, young trees showed a stronger sensitivity growth response towards climate variability (Hadad et al. 2015).
Araucaria araucana is a wind-pollinated species that shows an environmentally
triggered, intermittent, moderately fluctuating and regionally synchronous seed production pattern (Sanguinetti and Kitzberger 2008). Drought conditions in December,
during bud differentiation, acts as an environmental cue triggering mast events
24 months later and with a 3–7-year frequency (Sanguinetti and Kitzberger 2008;
Sanguinetti 2014). This reproductive spatiotemporal pattern, enhanced by the synchrony among pollen and seed production, maximizes the wind pollination efficiency, alternatively produces the starvation and satiation on the granivory
assemblage species and ultimately determines a typical seedling establishment pulse
after mast years (Shepherd and Ditgen 2005, 2012; Shepherd et al. 2008; Sanguinetti
and Kitzberger 2009; Díaz et al. 2012). In this way, Pewen pollen and cone production provides pulses of resources that control the distribution, reproduction and
abundance of native species along the food web, including those species that disperse their seeds (Shepherd and Ditgen 2005, 2012; Sanguinetti and Kitzberger
2009; Tella et al. 2016). However, forest understory degradation and seed consumption by livestock and wild non-native animal species, together with over- collecting
of seeds by humans, modified the natural seed survivorship and seedling establishment pattern. Therefore, habitat conditions for native species and their role within
the ecological processes changed (Sanguinetti 2008; Sanguinetti and Kitzberger
2010; Zamorano-Elgueta et al. 2012; Shepherd and Ditgen 2013, 2016; Tella et al.
2016; Szymañski et al. 2017; Milesi et al. 2017; Speziale et al. 2018).
Araucaria araucana is adapted to stressful conditions imposed by chronically
low resource availability, water deficit, extreme temperatures or light limitations
(Veblen et al. 1995). Their thick bark, epicormics buds that sprout after disturbance,
terminal buds protected by modified leaves and long roots allow the species to resist
strong winds, mudflows or wildfires. It showed a long leaf life span and an extremely
slow foliage turnover that together with the self-thinning behaviour over lower
branches and the ability to produce successively stem reiterations allows seedling
and sapling survivorship in the shade condition for decades until a canopy gap is
created.
7 Araucaria araucana and Salix humboldtiana…
the Andes, with fires occurring firstly in Argentina. However, the active disturbance
period stopped sooner in Argentina due to an earlier implementation of protected
areas (Mundo et al. 2013).
The growth of A. araucana is controlled by climatic signals where tree diameter
increased in years with cool and wet springs and summers (Villalba et al. 1989;
Mundo et al. 2012; Muñoz et al. 2014). However, the response on diameter growth
due to climate variability induced by “La Niña” events and SAM conditions varied
among sex and tree age (Hadad 2014; Hadad et al. 2015). On female trees, the positive conditions for growth are necessary during previous and current year (so control by “La Niña” event in the previous year). However, on male trees, only cool
temperatures in the previous year and humid conditions during the current year
promote diameter growth (so control by SAM conditions during growth). On the
other hand, young trees showed a stronger sensitivity growth response towards climate variability (Hadad et al. 2015).
Araucaria araucana is a wind-pollinated species that shows an environmentally
triggered, intermittent, moderately fluctuating and regionally synchronous seed production pattern (Sanguinetti and Kitzberger 2008). Drought conditions in December,
during bud differentiation, acts as an environmental cue triggering mast events
24 months later and with a 3–7-year frequency (Sanguinetti and Kitzberger 2008;
Sanguinetti 2014). This reproductive spatiotemporal pattern, enhanced by the synchrony among pollen and seed production, maximizes the wind pollination efficiency, alternatively produces the starvation and satiation on the granivory
assemblage species and ultimately determines a typical seedling establishment pulse
after mast years (Shepherd and Ditgen 2005, 2012; Shepherd et al. 2008; Sanguinetti
and Kitzberger 2009; Díaz et al. 2012). In this way, Pewen pollen and cone production provides pulses of resources that control the distribution, reproduction and
abundance of native species along the food web, including those species that disperse their seeds (Shepherd and Ditgen 2005, 2012; Sanguinetti and Kitzberger
2009; Tella et al. 2016). However, forest understory degradation and seed consumption by livestock and wild non-native animal species, together with over- collecting
of seeds by humans, modified the natural seed survivorship and seedling establishment pattern. Therefore, habitat conditions for native species and their role within
the ecological processes changed (Sanguinetti 2008; Sanguinetti and Kitzberger
2010; Zamorano-Elgueta et al. 2012; Shepherd and Ditgen 2013, 2016; Tella et al.
2016; Szymañski et al. 2017; Milesi et al. 2017; Speziale et al. 2018).
Araucaria araucana is adapted to stressful conditions imposed by chronically
low resource availability, water deficit, extreme temperatures or light limitations
(Veblen et al. 1995). Their thick bark, epicormics buds that sprout after disturbance,
terminal buds protected by modified leaves and long roots allow the species to resist
strong winds, mudflows or wildfires. It showed a long leaf life span and an extremely
slow foliage turnover that together with the self-thinning behaviour over lower
branches and the ability to produce successively stem reiterations allows seedling
and sapling survivorship in the shade condition for decades until a canopy gap is
created.
7 Araucaria araucana and Salix humboldtiana…