A demographic study was carried out on Bertholletia excelsa, the Brazil nut tree, in two primary forest
sites in Northern Bolivia where Brazil nuts have been harvested for several decades. In spite of the large proportion
(93%) of seeds that are harvested, reasonable densities of recently emerged seedlings were found. Seeds of Bertholletia
are contained in woody fruits that are primarily opened by agoutis. Most fruits are left untouched on the forest floor
for 1–2 y before they are opened, possibly due to high energetic costs of fruit opening just after fruit fall. However,
the proportion of viable seeds is strongly reduced in older fruits.Growth in diameter at breast height (dbh) was low for pole-sized trees (< 15 cm dbh) and adult trees (> 100 cm
dbh) and peaked for intermediate-sized trees (30–60 cm). These trees often attained a growth rate of > 1.5 cm y−1,
which is high compared with other non-pioneer tropical trees. This, and the strong growth response to increased light
availability found for seedlings and saplings, suggest that Bertholletia excelsa can be classified as a gap-dependent
species. Matrix population models were constructed for both study populations. Population growth rates (λ) were close
to one, and were most sensitive to persistence in one size category. Age estimates revealed that age at first reproduction
(at dbh > 60 cm) amounts to over 120 y, and age in the last category (dbh > 160 cm) to almost 300 y. Given the
continuous rejuvenation of the population, the stable population size, the high age at maturity and the long reproductive
period, it is concluded that current levels of Brazil nut extraction may be sustained at least for several decades and
perhaps for even longer periods.
Litter production in a natural stand of Brazil nut trees (Bertholletia excelsa Bonpl.)
