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Abstract:
Oenocarpus bataua var. bataua is a key species in the tropical rain forests of South America because it is
one of the 10 most abundant tree species and one of most used by Amerindians. However, there is an
acute lack of verifiable information about the duration of some of its ontogenic phases, the exact age
of the palms, and the effect of gap formation on its spatial distribution. We employed 36 permanent plots
(PP) of 0.1 ha randomly distributed in a forest of 700 ha in the Colombian Andes, in which we inventoried
the stemmed palms at the establishment of the PP and after 13.4 years to study some ontogenic and
demographic traits of this species. We dated underground and aboveground stems using the 14C
bomb-effect and estimated the stem’s age by the rate of leaf-scar formation. We aimed at answering
the following questions: (i) what are the main morphological characteristics of the underground stem
and how long does it takes for its formation?; (ii) what is the pattern of its spatial distribution at the landscape
level, and what factors help to explain it?; (iii) is the population structure and demography associated
with the previous history of the forest?; (iv) is the first flowering a function of the vigour of the
palms?. We found that the underground stem of adult palms is usually obconical and reaches
73 ± 13 cm in length (±standard deviation). The duration of the establishment phase in eleven palms
was almost constant: 37.5 ± 0.7 years. The palms with smaller and larger diameters tend to flourish when
the stems are 18 and 7 years old (44–55 years old from seedlings), respectively. We found that this species
has a clumped spatial pattern. Several palms dated gave ages between 91 and 92 years, while others
about 53 years. The bell shaped frequency distribution of the palm’s length and age suggest a lack of
younger palms in this area. We interpret that both, the clumped spatial pattern and their age distribution,
are a legacy from past selective loggings that induced even-aged cohorts of palms at the landscape level.
This species is not in equilibrium because the population tends to be reduced through time given that its doubling time is 37.4 years and its half-life 29.3 years
