322
of adaptation of forest genetic resources to changing environmental conditions and
social requirements (Young et al. 1996, Bawa and Dayanandan 1998).
12.1 The Yungas Rainforest: Geographical Location,
Logging Background, Conservation Status, and Trade
The Yungas, a subtropical montane rainforest from Northwest of Argentina (NWA),
is a hotspot of biodiversity in this country, especially on the Upper Bermejo River
Basin (UBRB). It is known that the Yungas plays an important role in providing
vital environmental services such as watershed protection. This ecosystem is
between 400 and 2300 m asl, and it is located on the southernmost limit of the neotropical cloud forests, a major system in Latin America (Brown et al. 2001). It
occurs along a narrow and discontinuous belt throughout the Argentinean provinces
of Salta, Jujuy, and Tucumán, from 22° to 28° 15′ S. The Yungas has been ecologically subdivided into Northern, Central, and Southern sectors according to the
north–south orographic pattern of mountain ranges of Sierras Subandinas and
Sierras Pampeanas that precede, from east to west, the Andean Cordillera in
Argentina (Brown et al. 2001). The Northern sector covers the mountainous formations of Sierras de Santa Victoria and Zenta; the center sector covers the Sierras de
Lumbrera, Santa Barbara, Centinela, and Maíz Gordo, and the Southern sector covers the Sierras de Metán, Aconquija, and Medina (De la Sota 1972; Brown et al.
2001). These latitudinal sectors are separated by Chaco Serrano and show a clear
decrease in taxonomic diversity with an increasing latitude that has been principally
associated with less benign weather conditions toward Southern Yungas (De la Sota
1972; Cabrera 1994; Morales et al. 1995; Brown et al. 2001; Juárez et al. 2007).
In general, the climate is defined as humid subtropical, with a marked dry season
(May–October) (Hurtado et al. 2013). The altitudinal extension hosts a great heterogeneity of environmental characteristics, which is reflected in the composition and
specific richness of the vegetation decreasing from the basal point toward the summits. As for trees, their distribution in the altitudinal gradient responds first to
changes in precipitation and temperature, and second to local factors related to
topography and disturbances (Brown et al. 2001; Blundo et al. 2012). This vegetation type expands across a large altitudinal gradient, where tree species turnover
promotes the occurrence of three altitudinal belts with differentiable physionomic
and floristic characteristics. The basal zone is occupied by the “Selva Pedemontana,”
approximately between 400 and 900 m asl in the piedmont and low altitude mountains, occupying 1217 km
2
, with annual average rainfall of 820 mm (550–1400 mm)
and annual average temperature of 21.5 °C (maximum mean = 27.6 °C, minimum
mean = 15.4 °C). The tree species of highest commercial value such as Cedrela
balansae, Pterogyne nitens, and Amburana cearensis have practically disappeared;
on the contrary a notorious increase in the abundance of species like Anadenanthera
colubrina var. cebil, which is not palatable for livestock, is detected. Of the total
L. F. Fornes
of adaptation of forest genetic resources to changing environmental conditions and
social requirements (Young et al. 1996, Bawa and Dayanandan 1998).
12.1 The Yungas Rainforest: Geographical Location,
Logging Background, Conservation Status, and Trade
The Yungas, a subtropical montane rainforest from Northwest of Argentina (NWA),
is a hotspot of biodiversity in this country, especially on the Upper Bermejo River
Basin (UBRB). It is known that the Yungas plays an important role in providing
vital environmental services such as watershed protection. This ecosystem is
between 400 and 2300 m asl, and it is located on the southernmost limit of the neotropical cloud forests, a major system in Latin America (Brown et al. 2001). It
occurs along a narrow and discontinuous belt throughout the Argentinean provinces
of Salta, Jujuy, and Tucumán, from 22° to 28° 15′ S. The Yungas has been ecologically subdivided into Northern, Central, and Southern sectors according to the
north–south orographic pattern of mountain ranges of Sierras Subandinas and
Sierras Pampeanas that precede, from east to west, the Andean Cordillera in
Argentina (Brown et al. 2001). The Northern sector covers the mountainous formations of Sierras de Santa Victoria and Zenta; the center sector covers the Sierras de
Lumbrera, Santa Barbara, Centinela, and Maíz Gordo, and the Southern sector covers the Sierras de Metán, Aconquija, and Medina (De la Sota 1972; Brown et al.
2001). These latitudinal sectors are separated by Chaco Serrano and show a clear
decrease in taxonomic diversity with an increasing latitude that has been principally
associated with less benign weather conditions toward Southern Yungas (De la Sota
1972; Cabrera 1994; Morales et al. 1995; Brown et al. 2001; Juárez et al. 2007).
In general, the climate is defined as humid subtropical, with a marked dry season
(May–October) (Hurtado et al. 2013). The altitudinal extension hosts a great heterogeneity of environmental characteristics, which is reflected in the composition and
specific richness of the vegetation decreasing from the basal point toward the summits. As for trees, their distribution in the altitudinal gradient responds first to
changes in precipitation and temperature, and second to local factors related to
topography and disturbances (Brown et al. 2001; Blundo et al. 2012). This vegetation type expands across a large altitudinal gradient, where tree species turnover
promotes the occurrence of three altitudinal belts with differentiable physionomic
and floristic characteristics. The basal zone is occupied by the “Selva Pedemontana,”
approximately between 400 and 900 m asl in the piedmont and low altitude mountains, occupying 1217 km
2
, with annual average rainfall of 820 mm (550–1400 mm)
and annual average temperature of 21.5 °C (maximum mean = 27.6 °C, minimum
mean = 15.4 °C). The tree species of highest commercial value such as Cedrela
balansae, Pterogyne nitens, and Amburana cearensis have practically disappeared;
on the contrary a notorious increase in the abundance of species like Anadenanthera
colubrina var. cebil, which is not palatable for livestock, is detected. Of the total
L. F. Fornes