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production of solid wood to supply the market for sleepers, rural constructions,
posts, and firewood; (2) enrichment and restoration of the remaining native forest;
and (3) tannin production. Studies on the genetic variation patterns of the species,
its genetic relationship with S. lorentzii in the contact area, methodologies for the
identification of hybrids and an ecophysiological background are needed to advance
toward the identification and creation of base materials. The identification of natural
seed- producing areas should be the first action for a conventional low-intensity
breeding program.
The approach toward tannin production changes the paradigm of forest production for timber purposes. The dimensions of the material to be produced are no
longer important; diameter and height disappear from the decision-making process.
The production of woody biomass in a rotation as short as possible and the tannin
content per unit of biomass become the main yield components in such an eventual
system. These particularities require the development of a specific forest genetic
improvement program. In this sense, planting at high densities selected material
with the following characteristics appears as a possible alternative production system:
• High density of heartwood
• Earliness of wood duraminization
• High tannin content in heartwood at early ages
• High initial growth
• High biomass production at equal basal area
• Low capacity of intraspecific competition (to enhance the duraminization process and increase the heartwood/sapwood ratio)
This intensive productive system (i.e., fertilization, soil tillage, weeding, diseases, and pest control) leads genetic improvement and silviculture to very particular approaches, including vegetative propagation and clonal forestry. According to
Giménez et al. (2000), from the moment heartwood begins to form, for each new
active growth ring, the heartwood also increases by one ring. Thus, the planting
density must be such that the plants compete at the moment of starting the
duraminization, in such a way that their growth decreases from that point, which
implies an increase in the heartwood/sapwood ratio.
Based on data from field trials of the tannin production company Unitán, located
in the provinces of Formosa and Chaco, Verga built growth curves in diameter, volume, and basal area and developed a high-density production model (4465 trees/ha,
no thinning) for S. balansae (not published). According to this model and to the
average content of tannin per ton of heartwood (38%) and of heartwood per ton of
logs, an annual harvest of 2315 ha would be sufficient to supply the mean annual
consumption of the two existing tannin industries. The rotation that maximizes
tannin production per ha under this model would be 20 years, therefore, a total of
46,302 ha of crop would be necessary, which is approximately a third of the surface
exploited today.
8 Subtropical Dry Forests: The Main Forest Ecoregion of Argentina
production of solid wood to supply the market for sleepers, rural constructions,
posts, and firewood; (2) enrichment and restoration of the remaining native forest;
and (3) tannin production. Studies on the genetic variation patterns of the species,
its genetic relationship with S. lorentzii in the contact area, methodologies for the
identification of hybrids and an ecophysiological background are needed to advance
toward the identification and creation of base materials. The identification of natural
seed- producing areas should be the first action for a conventional low-intensity
breeding program.
The approach toward tannin production changes the paradigm of forest production for timber purposes. The dimensions of the material to be produced are no
longer important; diameter and height disappear from the decision-making process.
The production of woody biomass in a rotation as short as possible and the tannin
content per unit of biomass become the main yield components in such an eventual
system. These particularities require the development of a specific forest genetic
improvement program. In this sense, planting at high densities selected material
with the following characteristics appears as a possible alternative production system:
• High density of heartwood
• Earliness of wood duraminization
• High tannin content in heartwood at early ages
• High initial growth
• High biomass production at equal basal area
• Low capacity of intraspecific competition (to enhance the duraminization process and increase the heartwood/sapwood ratio)
This intensive productive system (i.e., fertilization, soil tillage, weeding, diseases, and pest control) leads genetic improvement and silviculture to very particular approaches, including vegetative propagation and clonal forestry. According to
Giménez et al. (2000), from the moment heartwood begins to form, for each new
active growth ring, the heartwood also increases by one ring. Thus, the planting
density must be such that the plants compete at the moment of starting the
duraminization, in such a way that their growth decreases from that point, which
implies an increase in the heartwood/sapwood ratio.
Based on data from field trials of the tannin production company Unitán, located
in the provinces of Formosa and Chaco, Verga built growth curves in diameter, volume, and basal area and developed a high-density production model (4465 trees/ha,
no thinning) for S. balansae (not published). According to this model and to the
average content of tannin per ton of heartwood (38%) and of heartwood per ton of
logs, an annual harvest of 2315 ha would be sufficient to supply the mean annual
consumption of the two existing tannin industries. The rotation that maximizes
tannin production per ha under this model would be 20 years, therefore, a total of
46,302 ha of crop would be necessary, which is approximately a third of the surface
exploited today.
8 Subtropical Dry Forests: The Main Forest Ecoregion of Argentina