Growth and mortality of trees in Amazonian tropical rain forest in Ecuador

Abstract. Structural changes are analysed in four samples representing 4 ha, two line transects and two hectare plots, of Amazonian tropical lowland rain forest in northern Ecuador. Only trees with a DBH ≥ 10 cm were included. A sample of floodplain forest in Añangu represents the largest turnover found in tropical forests (stand half-life = 23 yr). The line transect and hectare plot both of tierra firme forest in Añangu have the same turnover (37 yr) and were balanced for death and in-growth of both individuals and wood (basal area). The 1-ha tierra firme sample in Cuyabeno had a turnover of 67 yr and was in a growing phase. The floodplain line transect in Añangu was in a phase of structural breakdown. However, the floodplain line transect had the largest growth of basal area per tree (23.4 cm²/yr). The tierra firme samples had a growth of 9.6, 10.1, and 13.6 cm²/yr. Most of the dead trees fell with some uprooting in three of the four samples. However, no significant difference in the distribution of mode of death was found between the four samples. Death was independent of topography and the dead trees were randomly distributed. As the trees grow up they occupy more space and larger trees (DBH ≥ 15 cm) become more uniformly distributed, whereas smaller trees (DBH ≤ 15 cm) were randomly distributed. Our study confirms that plots of 1 ha are not sufficient to include representative samples of different stages of forest structure.