4. Conclusions
Logging and the resulting changes in canopy
structure altered the composition of the stand,
reducing the number of shade tolerant species
and stimulating light demanding species. There
has been a nett increase in stem numbers and
stand basal area during the 11 year observation
period, and this trend has been echoed by most
of the individual species. The stand basal area 13
years after logging was about 75% of that in a
comparable unlogged primary forest. Logging
stimulated growth, but this effect was short-lived,
lasting only about 3 years, and current growth
rates are similar to those in unlogged primary
forest. Tree growth and timber production may
be enhanced by periodic silvicultural treatment
to release trees from competition and this should
be considered as a mechanism to reduce the cutting
cycles in the Brazilian Amazon.
The recognition of 29 additional species of
commercial importance raised the commercial
volume increment to 1.8 m3 ha-’ year-‘, but
further work will be necessary to confirm that this
production can be sustained on a 30-35 year cutting
cycle.
Results from the experiment reported here and
in related works, provide the first quantitative
information for management planning in the Ta
pajds Forest. These data will provide a useful
guide for choosing the cutting cycle and setting
the annual allowable cut. It has highlighted the
need to consider silvicultural treatment to stimulate
growth rates in forest areas zoned for timber
production. However, we caution that these
findings are drawn from observations over an 11
year period, and extrapolations to a 30-35 year
cutting cycle must be interpreted with caution.
Periodic remeasurement and analysis of these
plots over the next 30 years or more is necessary
to confirm these preliminary findings.
This case study has demonstrated just one
possible application of successive inventories.
Additional remeasurements on these and other
permanent sample plots in Amazonian terra
firme forest will provide a suitable database for
more detailed studies. Such studies may range
from the ecological to the commercial, from simple
analyses of changes between measures to dynamic
growth models linked to management
systems