The abiotic environment of Heliamphora nutans (Sarraceniaceae): pedological and microclimatic observations on Roraima Tepui

ABSTRACT

The aim of this study was the study of the abiotic environment of the carnivorous pitcher plant Heliamphora nutans (Sarraceniaceae), including the microclimate and the geochemistry of the soil of the growing sites on Roraima Tepui and discuss their relevance within the recent model of carnivorous plant ecology. The soil was peaty and low in nutrients. The microclimate on the site was very balanced, with moderately cool temperatures, a constant high humidity and very low wind speed. Heliamphora was not exposed to any recognizable climatic stress. Previous macroclimatic measurements reflected the growth conditions of Heliamphora only incorrectly, since humidity decreased drastically with height. The apparent conflict with the common model of carnivorous plant ecology was caused by the dense surrounding vegetation. However, the leaf coverage of these non carnivorous plants was too low to cause significant insolation decrease for Heliamphora. Furthermore, the temperature regime of the pitcher fluid was more balanced than the temperature of the leaf. This may improve conditions for the growth of microorganisms in the pitcher fluid that contribute to the degredation of the plant's prey.