Nitrogen supply frequently limits the forest productivity. Nitrogen-fixing lichens with a cyanobacterial photosynthetic partner (cyanolichens) growing as epiphytes in forest canopies have the potential to contribute significant amounts of nitrogen to forests, but the factors controlling their abundance are poorly understood. Long-term fertilization experiments in low-diversity Hawaiian montane rainforests indicate that epiphytic cyanolichens are most abundant and diverse when phosphorus supply to host trees is high, suggesting that soil phosphorus may indirectly determine epiphyte community composition and nitrogen inputs via canopy nitrogen fixation. The investigator will expand this research to investigate whether soil phosphorus also controls canopy epiphyte communities in highly diverse tropical forests on Mt. Kinabalu in Malaysian Borneo. This research will contribute towards understanding both the links between terrestrial soil and canopy processes and the role of canopy nitrogen fixation in whole-forest nutrient cycles.
