Forest structure and biomass recovery from windthrows in the Northwestern Amazon

Abstract:

Observations of forest recovery from natural disturbances in the Amazon are limited. Windthrows (uprooted and broken trees) are recurrent mode of tree mortality in the Amazon. The complex recovery process following windthrows has not been assessed in the Northwestern Amazon (NWA) which limits our understanding of natural forest dynamics in the basin. The NWA is characterized by high rate of windthrows, high soil nutrients, high rainfall, high productivity and no dry season. Using inventory data in three 3ha plots, we compared biomass in areas affected 2, 12 and 22 years following a large windthrow event in the region of Iquitos, Peru in the northwest Amazon. Old-growth forest in this region is characterized by tree density of 594 + 154 trees ha^-1 (trees >10 cm diameter at breast height) basal area of 25.79 +1.58 m² ha^-1 with biomass of 353 + 29.9 Mg ha^-1. Two years after windthrow disturbance, the biomass in the most disturbed area was reduced to 151.03 + 44.52 Mg ha^-1, however stem density, diameter, basal area and biomass recovered to old-growth values after 20 years (range 17 to 22 years). This rate of recovery is ∼50% faster than was derived from a similar study in the Central Amazon, The fast recovery of biomass in the Iquitos region may be associated with higher productivity in this region or to species composition differences between the areas. This study highlights the regional variability of forest dynamics in the Amazon.