Lianas represent a unique growth form that epitomizes tropical forest ecosystems. Here I test the hypothesis that liana seedlings will vary in canopy architecture, physiology, and responses to nutrient addition compared to tree seedlings. Lianas do not rely on their own stems for the majority of their support nor to gain entrance into the upper canopy, but rather they climb other vegetation. Due to biomass allocation patterns that result in reduced allocation to stem biomass and increased allocation to leaf and root tissue, lianas are expected to have fundamentally different physiological constraints compared to trees. It has also been suggested that differences in canopy architecture that maximizes shading of competing vegetation while minimizing self-shading may account for success of lianas compared to trees. Alteration of nutrient regime is an increasingly recognized component of global change, and lianas have already been shown to have relatively greater responses to other aspects of global change including CO₂ concentration, decreased precipitation and disturbance. Additionally, it has been predicted that as liana abundance increases, the carbon storage capacity of tropical forests will decline. In this study, I compared canopy architecture between 6 tree and 7 liana seedlings and in response to a full factorial N, P, K addition experiment in a lowland tropical forest within the Barro Colorado Nature Monument in Panama. Electron transport rate (ETR) was also measured as a measure of efficiency of photosystem II.

Results/Conclusions

Preliminary results show that lianas have greater leaf petiole length, leaf angle, leaf thickness, canopy depth and ETRmax than trees. In this study there was no affect of N alone, but addition of P increased ETRmax, and K increased plant height. These results suggest that variation in canopy architecture and ETR may help to explain the success of lianas in tropical forests. Effects of P and K shown in this study may have important implications for carbon gain and growth of tropical seedlings.