PS 7-63
Growth and physiological response of tropical lianas and trees to elevated CO2 and soil nutrient availability

Monday, August 5, 2013
Exhibit Hall B, Minneapolis Convention Center
David C. Marvin, Department of Global Ecology, Carnegie Institution for Science, Stanford, CA
Elise Morrison, Department of Soil and Water Science, University of Florida, Gainsville, FL
Andrew Quebbeman, Biology, Indiana University, Bloomington, IN
Benjamin L. Turner, Smithsonian Tropical Research Institute, Ancon, Panama
Klaus Winter, Smithsonian Tropical Research Institute, Panama

The recent increase in the abundance and size of native lianas (woody climbing vines) in tropical forests may lead to changes in species community composition and decreased carbon storage capacity. Lianas are associated with an increased risk of tree mortality and decreased tree growth due to intense above and belowground competition with trees for light, water, and soil nutrients. Increasing atmospheric CO2 and nitrogen deposition are potential drivers of the liana increase. Phosphorus availability, often assumed to be of key importance in constraining the productivity of lowland tropical forests, may decline as a consequence of increased nitrogen deposition. Our goal was to determine whether there is any difference in the growth and physiological response of tropical lianas and trees under elevated CO2, and whether any response differs as soil nitrogen and phosphorus availability change. We investigated locally abundant tropical liana and tree species grown in open-top chambers in Panama, half of which were maintained at twice-ambient levels of CO2. In two separate studies, seedlings were grown in pots with either reduced soil nitrogen or phosphorus. Half the pots in each experiment received weekly nutrient additions to return soil nutrients to current levels found in neotropical forests. 


The relative effect of CO2 on the response of lianas tended to be larger under low phosphorus conditions, although not always statistically significant. Nitrogen fertilization interacted with elevated CO2 to produce significant differences in liana vs. tree height and leaf area. Variation within species and across treatments was very high, and lianas gained relatively more stem height and leaf area than trees under elevated CO2 alone. These results suggest lianas will continue to increase as elevated CO2 rises and phosphorus limitation is strengthened by increasing nitrogen deposition.