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

Abstract

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 m2 versus 15 m2) or stem volume (214 m3 versus 52 m3), 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.