274
timber moldings, and furniture. On the other hand, planting density plays an essential role in branching degree, since denser plantations generate fewer branches and
straighter stems. Zárate et al. (2019) tested different pruning treatments under a
range of densities extending from 450 to 4500 plants/ha in a Nelder plot design,
showing that growth up to 7 years in plantations at low densities (450, 560, and
750 pl/ha) have potential to achieve the highest bole volumes per plant and with few
knots in the wood.
Another silvicultural treatment that should be used in any Prosopis plantation is
thinning. The aim is to redistribute the growth of the stand in the best possible way,
regulating the use of resources (water, light, and nutrients) in their growth space.
The remaining individuals increase their growth in response to thinning, concentrating the stand growth on a smaller number of trees, but of higher quality, thus increasing the value of the produced wood. One of the limitations for decision-making is
the opportune moment of thinning, which is carried out by evaluating the curves of
current annual increment (CAI) and mean annual increment (MAI). For plantations
in the Chaco region, the appropriate time for thinning ranges from 9 to 13 years.
This variation is mainly due to the initial planting density (Gómez et al. 2019).
Other factors that influence growth curves (CAI, MAI) are the seed provenance
(genetics) and site quality (environment). Applying this silvicultural management, a
rotation age of 25 years can be estimated, with diameters greater than 30 cm in the
best quality sites (Kees et al. 2018).
10.2 Low-Intensity Breeding
Afforestation plans with Prosopis requires a large volume of seeds every year, and
to supply this demand, fruits from the natural forest are collected. However, when
collecting seeds, interspecific crosses that occur naturally within the genus must be
avoided because can generate unevenness plantations, both in diameter and height
growth, as well as great variation in morphological characters (e.g., multibranches
or thorns). Like in all wild species, diversity is very large, which might constitute an
advantage for breeding, but, at the same time, it forces to reduce variability in order
to achieve discrete, more stable, and uniform genetic units. Therefore, the main
objective of the low-intensity breeding of Prosopis is to assure the proper amount of
seeds for seedling production, guaranteeing a high specific purity and uniformity of
the seedlings. The genetic and ecophysiological knowledge available on Prosopis
chilensis, P. flexuosa, and, more recently, P. alba, constitute the conceptual basis for
advancing toward the implementation of seed stands for these purposes.
Given the alarming loss of forests that has occurred in Argentina during the last
35 years (estimated in 12 million ha in the Chaco region, e.g., Spensley et al. 2013,
see Chap. 8), and the risk of losing biodiversity due to climate change, specific studies are required to identify and delimit seed production areas (SPA) for each species,
and its subsequent transformation into seed stands. These actions aim to preserve
existing variability and obtain base material with greater genetic uniformity and
D. López Lauenstein et al.
timber moldings, and furniture. On the other hand, planting density plays an essential role in branching degree, since denser plantations generate fewer branches and
straighter stems. Zárate et al. (2019) tested different pruning treatments under a
range of densities extending from 450 to 4500 plants/ha in a Nelder plot design,
showing that growth up to 7 years in plantations at low densities (450, 560, and
750 pl/ha) have potential to achieve the highest bole volumes per plant and with few
knots in the wood.
Another silvicultural treatment that should be used in any Prosopis plantation is
thinning. The aim is to redistribute the growth of the stand in the best possible way,
regulating the use of resources (water, light, and nutrients) in their growth space.
The remaining individuals increase their growth in response to thinning, concentrating the stand growth on a smaller number of trees, but of higher quality, thus increasing the value of the produced wood. One of the limitations for decision-making is
the opportune moment of thinning, which is carried out by evaluating the curves of
current annual increment (CAI) and mean annual increment (MAI). For plantations
in the Chaco region, the appropriate time for thinning ranges from 9 to 13 years.
This variation is mainly due to the initial planting density (Gómez et al. 2019).
Other factors that influence growth curves (CAI, MAI) are the seed provenance
(genetics) and site quality (environment). Applying this silvicultural management, a
rotation age of 25 years can be estimated, with diameters greater than 30 cm in the
best quality sites (Kees et al. 2018).
10.2 Low-Intensity Breeding
Afforestation plans with Prosopis requires a large volume of seeds every year, and
to supply this demand, fruits from the natural forest are collected. However, when
collecting seeds, interspecific crosses that occur naturally within the genus must be
avoided because can generate unevenness plantations, both in diameter and height
growth, as well as great variation in morphological characters (e.g., multibranches
or thorns). Like in all wild species, diversity is very large, which might constitute an
advantage for breeding, but, at the same time, it forces to reduce variability in order
to achieve discrete, more stable, and uniform genetic units. Therefore, the main
objective of the low-intensity breeding of Prosopis is to assure the proper amount of
seeds for seedling production, guaranteeing a high specific purity and uniformity of
the seedlings. The genetic and ecophysiological knowledge available on Prosopis
chilensis, P. flexuosa, and, more recently, P. alba, constitute the conceptual basis for
advancing toward the implementation of seed stands for these purposes.
Given the alarming loss of forests that has occurred in Argentina during the last
35 years (estimated in 12 million ha in the Chaco region, e.g., Spensley et al. 2013,
see Chap. 8), and the risk of losing biodiversity due to climate change, specific studies are required to identify and delimit seed production areas (SPA) for each species,
and its subsequent transformation into seed stands. These actions aim to preserve
existing variability and obtain base material with greater genetic uniformity and
D. López Lauenstein et al.