Floristic composition, structure, and dynamics of an upper montane rain forest in Southern Ecuador

Two 1 ha plots of undisturbed upper montane rain forest in southern Ecuador were sampled for all trees with a dbh ≥ 5 cm. An extraordinarily high α‐diversity for a forest near treeline is described. The “non‐ridge forest” plot at 2900 m elevation has 75 species and 28 families ha ‐1 and is believed to represent an advanced stage of succession whereas, the “ridge forest” plot at 2700 m elevation with 90 species and 38 families ha ‐1 has a more rapid turn‐over rate probably due to a more unstable environment. Downslope forces (soil creep) are discussed as a possible cause for 32–44% of all trees being inclined more than 30° in the moderately steep terrain (average slope 20° in both study plots). The plot of “non‐ridge forest” is characterized by a much greater biomass whether expressed as basal area (44 m 2 versus 15 m 2 ) or stem volume (214 m 3 versus 52 m 3 ), while the density is equally high (2310 versus 2090 trees ha ‐1 ) in both plots. Families with Family Importance Value >25 / ha ‐1 are Clusiaceae, Cunoniaceae, Melastomataceae, Myrsinaceae, and Ternstroemiaceae.