197
unprecedented event affected the native S. humboldtiana populations in advanced
rather than early successional stages, due to the massive invasion of P. nigra cv.
italica, occupying the sand banks that are necessary for the native willow’s sexual
regeneration. Energy dams in some of the Patagonian rivers avoid the consolidation
of sand and lime banks that are essential for the establishment of S. humboldtiana
seedlings. Similarly, in the river basins of Futaleufú River and Chubut River, a high
density of interspecific exotic hybrids was found (Orellana et al. 2016), and mechanical and chemical methods to control the exotic willows’ invasion were proposed
(Amico and Orellana 2014).
Salix x fragilis f. fragilis (previously called S. x rubens) is the natural hybrid
between Salix alba L. and Salix euxina I. (ex S. fragilis) (Belyaeva 2009) and has an
extraordinary vegetative propagation capacity. A study with molecular markers
determined that in the Patagonian rivers, most of the willow trees (93%) belong to
the same and only female clone of Salix x fragilis f. fragilis (Budde et al. 2011). In
a greenhouse experiment, an inferior vegetative propagation capacity of S. humboldtiana was observed when compared with exotic introduced clones (S. x fragilis
f. fragilis, S. babylonica hybrid) and Populus spp., under different humidity conditions (Thomas et al. 2012; Fig. 7.10).
In Patagonia, hydro-geomorphological processes regulate the plant succession
on floodplains, establishing a zoning associated with river geoforms. They are frequently flooded and normally covered by plant communities that change through
time. Pioneer vegetation is highly adapted to extremely variable river flows and
morphology (Gray et al. 2006) and can trap and stabilize sediments that influence
their own distribution patterns in the river channel. A closer and more complex
interplay between riparian trees, woody debris, flood pulses, sedimentation, and
island development results in new plant systems that grow by sexual and vegetative
reproduction (Datri et al. 2016a, 2017).
Fig. 7.10 Comparative
vegetative propagation
capacity of
S. humboldtiana cuttings
vs. exotic willows and
poplars along a humidity
gradient in a greenhouse
experiment. (From Thomas
et al. 2012). (S. x rubens is
at present named S. x
fragilis f. fragilis)
7 Araucaria araucana and Salix humboldtiana…
unprecedented event affected the native S. humboldtiana populations in advanced
rather than early successional stages, due to the massive invasion of P. nigra cv.
italica, occupying the sand banks that are necessary for the native willow’s sexual
regeneration. Energy dams in some of the Patagonian rivers avoid the consolidation
of sand and lime banks that are essential for the establishment of S. humboldtiana
seedlings. Similarly, in the river basins of Futaleufú River and Chubut River, a high
density of interspecific exotic hybrids was found (Orellana et al. 2016), and mechanical and chemical methods to control the exotic willows’ invasion were proposed
(Amico and Orellana 2014).
Salix x fragilis f. fragilis (previously called S. x rubens) is the natural hybrid
between Salix alba L. and Salix euxina I. (ex S. fragilis) (Belyaeva 2009) and has an
extraordinary vegetative propagation capacity. A study with molecular markers
determined that in the Patagonian rivers, most of the willow trees (93%) belong to
the same and only female clone of Salix x fragilis f. fragilis (Budde et al. 2011). In
a greenhouse experiment, an inferior vegetative propagation capacity of S. humboldtiana was observed when compared with exotic introduced clones (S. x fragilis
f. fragilis, S. babylonica hybrid) and Populus spp., under different humidity conditions (Thomas et al. 2012; Fig. 7.10).
In Patagonia, hydro-geomorphological processes regulate the plant succession
on floodplains, establishing a zoning associated with river geoforms. They are frequently flooded and normally covered by plant communities that change through
time. Pioneer vegetation is highly adapted to extremely variable river flows and
morphology (Gray et al. 2006) and can trap and stabilize sediments that influence
their own distribution patterns in the river channel. A closer and more complex
interplay between riparian trees, woody debris, flood pulses, sedimentation, and
island development results in new plant systems that grow by sexual and vegetative
reproduction (Datri et al. 2016a, 2017).
Fig. 7.10 Comparative
vegetative propagation
capacity of
S. humboldtiana cuttings
vs. exotic willows and
poplars along a humidity
gradient in a greenhouse
experiment. (From Thomas
et al. 2012). (S. x rubens is
at present named S. x
fragilis f. fragilis)
7 Araucaria araucana and Salix humboldtiana…