401
Anselmini and Zanette (2012) in this species showed that the maximum capacity to
produce cones is given by the availability of pollen.
A. angustifolia is a dioecious and anemophilous species; the male gamete in the
pollen grain produced by a male tree is windblown to the female cones of another
tree. The reproductive cycle starts with strobilus formation in November and finishes when the main pollination occurs in October of the following year. Twenty
months thereafter, the seeds are mature, so a total of about 30 months are needed to
complete the entire process. During this long period, climatic conditions vary offering at each stage a new chance of failure of the reproductive process.
15.4.1 Limitations for the Pollination and Seed Formation
Important limitations in the pollen amounts for the pollination of A. angustifolia can
be observed in two dimensions: (1) the decrease in pollen productivity that may be
associated with previous temperature (Caccavari et al. 2000; Bittencourt and
Sebbenn 2007) and (2) the scarce dispersion of pollen grains due to (2a) their substantial size and weight (Caccavari 2003), (2b) the low number of trees and the
distance between them, and (2c) unfavorable weather conditions affecting the displacement of pollen grains (Latorre et al. 2013).
For anemophilous species with nonspecific pollination, one of the strategies that
guarantees effective fertilization is the large amount of pollen (Faegri and van der
Pijl 1979). Latorre et al. (2020) observed for A. angustifolia in Manuel Belgrano
Forest Station using a 7-day Burkard aerobiologic trap, an alternation between
1 year of high pollen values (1685 pollen grains.day
−1
.m
−3
air, on average), followed
by 2 years of a progressive reduction in intensity (456 pollen grains.day
−1
.m
−3
air, on
average), a decline exceeding 50%. The relevance of detecting the years of increased
production lies in the possibility of implementing management decisions, such as
cleaning the understory during the year after the highest pollen values and collect
the seeds for seedling production in the nursery or allow seedlings to germinate
naturally and develop free of competition after the second year following the high
pollen productivity.
Latorre et al. (2016) postulate the negative effect that high temperatures prior to
pollination have on the number of pollen grains. The correlation between pollen
production and the average minimum temperature of August is negative (r = −0.75,
p = 0.05), supporting the key role that the environment plays on the species phenology (Fig. 15.4). The lower minimum temperature of August prior to pollination
match with the higher pollen production recorded for that year, adjusting to a predictive equation in 80% of the cases, p = 0.004 (Latorre et al. 2020). Since seed
production results from a successful fertilization that occurs 2 years before
(Anselmini 2005), this statistical model could help estimate seed productivity
20 months ahead.
To evaluate the effect of climate on the pollen productivity of A. angustifolia,
Simón et al. (2018) compared two old plantations growing under different climate
15 Paraná Pine (Araucaria angustifolia): The Most Planted Native Forest Tree…
Anselmini and Zanette (2012) in this species showed that the maximum capacity to
produce cones is given by the availability of pollen.
A. angustifolia is a dioecious and anemophilous species; the male gamete in the
pollen grain produced by a male tree is windblown to the female cones of another
tree. The reproductive cycle starts with strobilus formation in November and finishes when the main pollination occurs in October of the following year. Twenty
months thereafter, the seeds are mature, so a total of about 30 months are needed to
complete the entire process. During this long period, climatic conditions vary offering at each stage a new chance of failure of the reproductive process.
15.4.1 Limitations for the Pollination and Seed Formation
Important limitations in the pollen amounts for the pollination of A. angustifolia can
be observed in two dimensions: (1) the decrease in pollen productivity that may be
associated with previous temperature (Caccavari et al. 2000; Bittencourt and
Sebbenn 2007) and (2) the scarce dispersion of pollen grains due to (2a) their substantial size and weight (Caccavari 2003), (2b) the low number of trees and the
distance between them, and (2c) unfavorable weather conditions affecting the displacement of pollen grains (Latorre et al. 2013).
For anemophilous species with nonspecific pollination, one of the strategies that
guarantees effective fertilization is the large amount of pollen (Faegri and van der
Pijl 1979). Latorre et al. (2020) observed for A. angustifolia in Manuel Belgrano
Forest Station using a 7-day Burkard aerobiologic trap, an alternation between
1 year of high pollen values (1685 pollen grains.day
−1
.m
−3
air, on average), followed
by 2 years of a progressive reduction in intensity (456 pollen grains.day
−1
.m
−3
air, on
average), a decline exceeding 50%. The relevance of detecting the years of increased
production lies in the possibility of implementing management decisions, such as
cleaning the understory during the year after the highest pollen values and collect
the seeds for seedling production in the nursery or allow seedlings to germinate
naturally and develop free of competition after the second year following the high
pollen productivity.
Latorre et al. (2016) postulate the negative effect that high temperatures prior to
pollination have on the number of pollen grains. The correlation between pollen
production and the average minimum temperature of August is negative (r = −0.75,
p = 0.05), supporting the key role that the environment plays on the species phenology (Fig. 15.4). The lower minimum temperature of August prior to pollination
match with the higher pollen production recorded for that year, adjusting to a predictive equation in 80% of the cases, p = 0.004 (Latorre et al. 2020). Since seed
production results from a successful fertilization that occurs 2 years before
(Anselmini 2005), this statistical model could help estimate seed productivity
20 months ahead.
To evaluate the effect of climate on the pollen productivity of A. angustifolia,
Simón et al. (2018) compared two old plantations growing under different climate
15 Paraná Pine (Araucaria angustifolia): The Most Planted Native Forest Tree…