Floristics and physical structure of five Amazon plots in Ecuador and Peru

Resumen

The Amazon contains some of the most important forested ecosystems on earth and so we need to know the nature and degree of their similarities and differences.  Therefore, I compared the floristics and physical structure of five common Amazonian forest-types (terra firme, palm and white sand [all unflooded], várzea and igapó [both flooded]) with data from separate one ha plots in the Ecuadorean and Peruvian Amazon.  I found (1) the most abundant families were Arecaceae, Fabaceae, and Clusiaceae and those families along with Euphorbiaceae were the only families found in all five plots, (2) the highest stem density, the greatest number of large stems and the most closed canopy were in várzea and terra firme, (3) palm had the most median stems and the smallest average stem size, and (4) igapó had the smallest basal area and above-ground biomass.  Ordination on the five plots then suggested that Arecaceae and Clusiaceae best defined the floristic data, and total stems and smallest stem size class best defined the physical structure data.  Cluster analysis after ordination (1) based on floristics, showed that terra firme, várzea and igapó formed a cluster and both palm and white sand were in separate clusters by themselves, and (2) based on physical structure, showed that terra firme and palm formed a cluster, white sand and igapó formed a cluster and várzea was in a cluster by itself.  While results suggest that soil characteristics are important in determining the floristic composition of Amazon forests and flooding characteristics are important in determining their physical structure, they can only set-up hypotheses to test by future sampling of these forest-types elsewhere in the Amazon.