Successive inventories of a silvicultural experiment in terra firme rain forest within the
Tapajós National Forest in the Brazilian Amazon are examined to provide guidelines for
operational forest management on a sustainable basis. The experiment was logged in
1979 without additional silvicultural treatment, but included protection from further
logging and encroachment (`log and leave’). Thirty-six permanent plots established in
1981 were remeasured in 1987 and 1992.
Logging changed the canopy structure and altered the composition of the stand,
reducing the number of shade tolerant species and stimulating light demanding
species. There was a net increase in stem number and stand basal area during the 11
year observation period, and this trend also holds for most of the individual species.
The stand basal area 13 years after logging was about 75% of that in a comparable
unlogged forest. Logging stimulated growth, but this effect was short-lived, lasting only
about 3 years, and current growth rates are similar to those in the unlogged forest.
Between the first and second remeasures, average diameter increment decreased from
0.4 to 0.2 cm year-1, mortality remained relatively constant at 2.5% year-1, while
recruitment (at 5 cm diameter at breast height) decreased from 5 to 2%. Total volume
production declined from approximately 6 to 4 m3 ha-1 year-1, while commercial
production remained about 0.8 m3 ha-1 year-1. New commercial species increased the
commercial volume in 1992 from 18 to 54 m3 ha-1, and the increment to 1.8 m3 ha-1
Results from this experiment provide the first quantitative information for management
planning in the Tapajós Forest, and may guide the choice of cutting cycle and annual
allowable cut. Silvicultural treatment to stimulate growth rates in forest areas zoned for
timber production should be considered as a viable management option. Extrapolations
of these results to an anticipated 30-35 year cutting cycle must be interpreted with
caution. Ongoing remeasurement and analysis of these and other plots over the next
30 years or more are necessary to provide a stronger basis for management inferences.
Topic: yields,growth,succession,forest inventories
Publication Year: 1995
Source: Forest Ecology and Management 71(3): 171-276