335
However, several exotic invasive species began to appear in expansion the last
30 years (Malizia et al. 2017; Montti et al. 2017; Powell and Aráoz 2018), mainly of
the genus Ligustrum, Morus, and Leucaena.
Many of the remaining Yungas rainforests diminished their productive potential
due to unplanned forest use, but, in addition, extensive livestock farming has negatively affected the regeneration of some forest species, encouraging the advance of
invasive species (Lorenzatti 2014). To reverse the economic and ecological degradation of many of the Yungas’ stands, changes have been proposed in forestry techniques to ensure sustainable forest management based on the natural dynamics of
species (Balducci et al. 2012). These proposed changes in Yungas management are
based on a Reduced Impact Logging (RIL) scheme – an adaptive management
framework. Implementing low impact forest management, including seed tree
selection and future tree protection, is important because conventional forest harvesting produces, among other negative impacts, damage to approximately 30 trees
for each extracted tree (Uhl 1990). This last strategy is suggested especially for the
Northern sector of the basal Yungas rainforest.
The differentiation of geographic sectors in the latitudinal gradient of Yungas
(North–Central–South) related mainly to species diversity and climatic and topographic conditions (Brown and Kappelle 2001; Blundo et al. 2012) is consistent
with the genetic zones identified by Inza et al. (2012) for Cedrela angustifolia. This
differentiation suggests diverse approaches for the Northern and Central–Southern
sectors related to the forest management and restoration methods (Chap. 13). The
same trend is observed in Handroanthus impetiginosus (see Chap. 16). The most
noticeable change, considering specific biodiversity, forest structure, and genetic
diversity, occurs at a latitude of around 24° S. Between 24° and 28°15′ S, the
Argentinean Yungas shows in general an impoverishment in terms of the number of
commercially valuable species, but also in the magnitude of the population genetic
diversity of emblematic species.
Given the above conditions, enrichment with native species of high commercial
value is a valid and sustainable alternative in places where land use change is not
legally feasible (Yellow Zones, according to the National Law 26,331) either
through the opening of narrow trails leaving strips of secondary forest or in agroforestry systems, especially in the Central and South sectors.
Regarding the legal framework, National Law 26,331 of Minimum Requirements
for the Environmental Protection of Native Forests regulates the extraction of native
timber and the expansion of the agricultural frontier. This law represents a major
opportunity for the conservation of natural forests, as it restricts spaces in which
logging and land use changes are permitted. Additionally, it encourages the recovery and improvement of degraded forests, which helps to maintain the supply of
these types of hardwood to the market, based on sustainable production (Yellow
Zones), and, consequently, the ecosystem services offered by these forests.
According to forest management maps prepared by the provinces, at present, the
NWA region (Salta, Jujuy, and Tucumán) and Misiones represent approximately
1.5 million hectares suitable for enrichment through hardwood species in Yellow
Zones (Fornes 2012).
12 Subtropical Rainforests: The Yungas and the Alto Paraná Rainforest
However, several exotic invasive species began to appear in expansion the last
30 years (Malizia et al. 2017; Montti et al. 2017; Powell and Aráoz 2018), mainly of
the genus Ligustrum, Morus, and Leucaena.
Many of the remaining Yungas rainforests diminished their productive potential
due to unplanned forest use, but, in addition, extensive livestock farming has negatively affected the regeneration of some forest species, encouraging the advance of
invasive species (Lorenzatti 2014). To reverse the economic and ecological degradation of many of the Yungas’ stands, changes have been proposed in forestry techniques to ensure sustainable forest management based on the natural dynamics of
species (Balducci et al. 2012). These proposed changes in Yungas management are
based on a Reduced Impact Logging (RIL) scheme – an adaptive management
framework. Implementing low impact forest management, including seed tree
selection and future tree protection, is important because conventional forest harvesting produces, among other negative impacts, damage to approximately 30 trees
for each extracted tree (Uhl 1990). This last strategy is suggested especially for the
Northern sector of the basal Yungas rainforest.
The differentiation of geographic sectors in the latitudinal gradient of Yungas
(North–Central–South) related mainly to species diversity and climatic and topographic conditions (Brown and Kappelle 2001; Blundo et al. 2012) is consistent
with the genetic zones identified by Inza et al. (2012) for Cedrela angustifolia. This
differentiation suggests diverse approaches for the Northern and Central–Southern
sectors related to the forest management and restoration methods (Chap. 13). The
same trend is observed in Handroanthus impetiginosus (see Chap. 16). The most
noticeable change, considering specific biodiversity, forest structure, and genetic
diversity, occurs at a latitude of around 24° S. Between 24° and 28°15′ S, the
Argentinean Yungas shows in general an impoverishment in terms of the number of
commercially valuable species, but also in the magnitude of the population genetic
diversity of emblematic species.
Given the above conditions, enrichment with native species of high commercial
value is a valid and sustainable alternative in places where land use change is not
legally feasible (Yellow Zones, according to the National Law 26,331) either
through the opening of narrow trails leaving strips of secondary forest or in agroforestry systems, especially in the Central and South sectors.
Regarding the legal framework, National Law 26,331 of Minimum Requirements
for the Environmental Protection of Native Forests regulates the extraction of native
timber and the expansion of the agricultural frontier. This law represents a major
opportunity for the conservation of natural forests, as it restricts spaces in which
logging and land use changes are permitted. Additionally, it encourages the recovery and improvement of degraded forests, which helps to maintain the supply of
these types of hardwood to the market, based on sustainable production (Yellow
Zones), and, consequently, the ecosystem services offered by these forests.
According to forest management maps prepared by the provinces, at present, the
NWA region (Salta, Jujuy, and Tucumán) and Misiones represent approximately
1.5 million hectares suitable for enrichment through hardwood species in Yellow
Zones (Fornes 2012).
12 Subtropical Rainforests: The Yungas and the Alto Paraná Rainforest