PARENT SESSION
Friday, August 11, 8:00-11:30 am
COS 110 - Tropical ecology
Sultana, Mezzanine Level, Cook Convention Center
Presiders: G Selaya
Phosphorus fertilization stimulates bloom in nitrogen-fixing epiphytes in a Hawaiian montane rainforest.
Benner, Jon*,1, Vitousek, Peter1, 1 Stanford University, Stanford, CA
ABSTRACT- Nitrogen-fixing epiphytes (especially lichens with a cyanobacterial symbiont−cyanolichens) have the potential to contribute nitrogen to low-N montane tropical forests. However, the factors controlling the abundance and distribution of epiphytic cyanolichens are poorly understood. A long-term fertilization experiment in a P-limited montane forest on the island of Kauai yielded large increases in both abundance and diversity of cyanolichens in response to fertilization with P; there was no response to fertilization with N or other essential elements. A mean of 3.2% of the bark of the dominant host tree Metrosideros polymorpha is covered by cyanolichens in control and N plots, compared to 62.7% in P-fertilized plots (P effect, p<0.001). The average number of cyanolichen species per tree increased from 2.9 to 18.8 with P-fertilization (p<0.001). In addition, epiphytic lichens with green algal symbionts increased in percent cover (p<0.001) and species richness (p<0.001) with P-fertilization, and epiphytic mosses increased in species richness (p<0.001). The common cyanolichen Pseudocyphellaria crocata collected from fertilized plots had higher rates of nitrogenase activity following long-term P-fertilization, increasing from an average of 28.7 to 462.7 nanomoles ethylene produced per gram of lichen per hour. Phosphorus supply may be an important factor controlling both epiphyte diversity and N inputs to montane tropical forests by epiphytic cyanolichens.
Key words: tropical montane forest, nitrogen fixation, epiphytes