Forest dynamics in flood plain forests in the Peruvian Amazon: effects of disturbance and implications for management

Forest dynamics were studied from 1993 to 1997 for individuals > 10 cm DBH in nine 1 ha permanent sample plots. They were established in natural flood plain forests located on the lower Ucayali river in the Peruvian Amazon. After inventories of three plots in each of three forest types, a light and a heavy felling treatment were applied to each of the two plots, while a third plot was kept untreated. Average annual stem mortality and recruitment rates in the untreated plots were among the highest observed in neotropical rain forests: mortality 2.2-3.2% per year, recruitment 3.0-4.6% per year. Dead individuals deviated significantly from random dispersion towards clumping. The average annual basal area growth was around 1 m/ha per year, corresponding to average annual basal area growth rates of 3.5-3.8% per year in the untreated plots. No decrease in basal area growth was observed even in the treated plots where annual basal area mortality rates up to 41 % during the first year were observed. The average diameter growth increased from 4.0-4.5 mm per year in the untreated plots to 5.3-6.8 mm per year in the treated plots. The stocking of commercial timber species was high with basal areas of 2.6-10.0 m/ha and volumes of 59-240 m/ha. The corresponding growth of basal area and volume of commercial timber species were also considerable, reaching values of 0.1-0.3 m/ha per year and 2-9 m/ha per year, respectively. These attributes suggested that forest management for timber production in these forests can be flexible and provide relatively high yields on a sustained basis. It appeared that management interventions can be carried out within the range of naturally occurring perturbations, although it should be noticed that only limited proportions of each habitat are disturbed at a time by nature. The patchy occurrence of habitats may provide logistic problems to management.