233
it shares the dominant layer with the red quebrachos. In the arid Chaco, it is the only
dominant species. Here it has been verified that for its installation it requires the
facilitation of “nurse” plants, generally shrubs of the genus Larrea (Barchuk and
Díaz 2000).
Barchuk and Valiente-Banuet (2006) found significant differences in the specific
leaf area and in the leaf exposure angle among three populations of this species
located in humid, semi-arid, and arid Chaco. They demonstrated that populations in
more arid areas have a distribution of leaf angles closer to 90° (this increased the
frequency of individuals with pendulous branches) and a lower specific leaf area,
both factors that decrease water consumption. Likewise, Moglia and López (2001)
found that the xylem of this species in the semi-arid Chaco works “as an interconnected network,” where the vessels participate, guaranteeing a high efficiency in
driving, as well as the supporting elements form a subsidiary system that ensures
water conduction under conditions of high drought stress.
Regarding the genetic pattern of the species, Torres Basso (2014) evaluated the
distribution of its genetic diversity in the arid Chaco through the use of RAPDs
(Random Amplified Polymorphic DNA) molecular markers. He found an important
differentiation between relatively close populations (relative to its huge range), significant correlation between geographical and genetic distances, and a certain
grouping of populations with respect to their genetic composition based on the
hydric conditions of the studied sites. Recently, Messias et al. (2020) have developed 16 SSR markers for Aspidosperma pyrifolium, and transferred to 11 other
species of the genus, including A. quebracho-blanco, which is undoubtedly a significant contribution to the study of its genetic resources.
8.5.3 Enterolobium contortisiliquum (Fabaceae)
It is a 10–20 m high tree (it can reach 30 m), with an extended crown and deciduous
light green foliage, with bipinnate compound leaves (Slanis 2018). The trunk is
cylindrical, slightly tortuous, with a basal diameter of up to 1.5 m, with gray, smooth
bark. It has a wide range of distribution, across Brazil, Argentina, Uruguay, and
Paraguay. In Argentina it can be found in the piedmont of the Yungas, in the Alto
Paraná Rainforest, in the Chaco and in the Espinal (Fig. 8.9).
Its wood is light (specific weight: 0.39 kg/dm
3
) and resistant to water thanks to
its resin, which made the Wichí aborigines to used it to make canoes by hollowing
out their trunks. The heartwood is brown-pinkish in color, with yellowish sapwood
(Giménez and Moglia 2003a, b). It is used for openings, outdoor furniture and naval
carpentry. It is suitable for peeling and plywood manufacturing. As a tree it is
appreciated for its ornamental value and for the shade of its wide crown, which
makes it suitable for large green spaces. It is a fast growing species (up to 4 cm in
diameter and 2.5 m in height per year; Giménez and Moglia 2003a, b), and it has
been suggested for active restoration of degraded forests, especially in riparian areas
8 Subtropical Dry Forests: The Main Forest Ecoregion of Argentina
it shares the dominant layer with the red quebrachos. In the arid Chaco, it is the only
dominant species. Here it has been verified that for its installation it requires the
facilitation of “nurse” plants, generally shrubs of the genus Larrea (Barchuk and
Díaz 2000).
Barchuk and Valiente-Banuet (2006) found significant differences in the specific
leaf area and in the leaf exposure angle among three populations of this species
located in humid, semi-arid, and arid Chaco. They demonstrated that populations in
more arid areas have a distribution of leaf angles closer to 90° (this increased the
frequency of individuals with pendulous branches) and a lower specific leaf area,
both factors that decrease water consumption. Likewise, Moglia and López (2001)
found that the xylem of this species in the semi-arid Chaco works “as an interconnected network,” where the vessels participate, guaranteeing a high efficiency in
driving, as well as the supporting elements form a subsidiary system that ensures
water conduction under conditions of high drought stress.
Regarding the genetic pattern of the species, Torres Basso (2014) evaluated the
distribution of its genetic diversity in the arid Chaco through the use of RAPDs
(Random Amplified Polymorphic DNA) molecular markers. He found an important
differentiation between relatively close populations (relative to its huge range), significant correlation between geographical and genetic distances, and a certain
grouping of populations with respect to their genetic composition based on the
hydric conditions of the studied sites. Recently, Messias et al. (2020) have developed 16 SSR markers for Aspidosperma pyrifolium, and transferred to 11 other
species of the genus, including A. quebracho-blanco, which is undoubtedly a significant contribution to the study of its genetic resources.
8.5.3 Enterolobium contortisiliquum (Fabaceae)
It is a 10–20 m high tree (it can reach 30 m), with an extended crown and deciduous
light green foliage, with bipinnate compound leaves (Slanis 2018). The trunk is
cylindrical, slightly tortuous, with a basal diameter of up to 1.5 m, with gray, smooth
bark. It has a wide range of distribution, across Brazil, Argentina, Uruguay, and
Paraguay. In Argentina it can be found in the piedmont of the Yungas, in the Alto
Paraná Rainforest, in the Chaco and in the Espinal (Fig. 8.9).
Its wood is light (specific weight: 0.39 kg/dm
3
) and resistant to water thanks to
its resin, which made the Wichí aborigines to used it to make canoes by hollowing
out their trunks. The heartwood is brown-pinkish in color, with yellowish sapwood
(Giménez and Moglia 2003a, b). It is used for openings, outdoor furniture and naval
carpentry. It is suitable for peeling and plywood manufacturing. As a tree it is
appreciated for its ornamental value and for the shade of its wide crown, which
makes it suitable for large green spaces. It is a fast growing species (up to 4 cm in
diameter and 2.5 m in height per year; Giménez and Moglia 2003a, b), and it has
been suggested for active restoration of degraded forests, especially in riparian areas
8 Subtropical Dry Forests: The Main Forest Ecoregion of Argentina