Ecological traits of the tropical treeline species Polylepis quadrijuga (Rosaceae) in the Andes of Colombia

Abstract

Information is presented on the phenology, herbivory, phytochemistry and production of the tree species Polylepis quadrijuga. Leaf production was lower during the dry season than during the wet season, when minimum temperatures also occurred. Flower and fruit phenology were also seasonal. Herbivory was significantly higher for leaves expanded during the wet season (20%) than during the dry season (1%), and was also higher for younger leaves. Flavonoids, compounds known as UV-B protectors, were found in high concentration in leaves of P. quadrijuga. There was a significant positive relationship between monthly rainfall, monthly minimum temperatures and flavonoid concentration, but no relationship was found with leaf age. The annual fine litterfall for the Polylepis forest was estimated to be 3.9 t ha⁻¹ y⁻¹, a high value when compared to other paramo and upper montane rain forests in tropical mountains. High production was associated with high leaf nitrogen concentration (3.0–3.5%), high rates of nitrogen retranslocation (80% dry weight), and relatively low leaf longevity (8.4 mo). High production in P. quadrijuga is probably a key factor in explaining the existence of this large woody species in a paramo environment otherwise dominated by bunch grasses, cushion plants and giant rosettes of the genus Espeletia.