Litter fall, biomass and net primary production in flood plain forests in the Peruvian Amazon

During a 4-year period the biomass density and increment were studied in 1 ha permanent sample plots located in three flood plain forests and fine litter fall was collected weekly during 1 year. The low restinga, high restinga and tahuampa forests were situated on nutrient rich alluvial soils, and they were on the average inundated for 1, 2 and 4 months per year, respectively. The fine litter fall was around 700 g/m 2 per year in all three forests with a peak which was probably caused by the flooding. Leaves falling at the end of and just after the inundation had the lowest specific leaf areas (approximately 60 cm 2/g versus 110 cm 2/g). The average annual specific leaf area increased with decreasing average flooding period of the forests. Assuming a 12-month leaf duration the leaf area index was estimated to be 4.2–4.4. For trees larger than 10 cm diameter at breast height the standing wood volume was 662–750 m 3/ha with an increment of 23–28 m 3/ha per year. The average aboveground living biomass of the three forests was 34,493–48,691 g/m 2, and a NPP of 2082–2558 g/m 2 per year was registered, excluding losses to herbivory. A high level of wood biomass production was registered in comparison to other tropical rain forests (1709 g/m 2 per year versus 734 g/m 2 per year), which was noteworthy in consideration of the fact that growth processes of trees were inhibited several months each year during the flooding, and that this event coincided with the months of highest precipitation.