PARENT SESSION
Oral Session #5: Ecosystem processes: Decomposition and litter. Presiding: K. Lajtha.
Monday, August 6, 2001. 8:00 AM to 12:15 PM. Hall of Ideas E.
Polyphenols in tropical rainforest litter.
HATTENSCHWILER, STEPHAN1, VITOUSEK, PETER2, 1 2
ABSTRACT- It has been proposed that plant-derived polyphenols may increase plant available soil nutrients in infertile ecosystems. We addressed the question whether litter polyphenol concentrations correlate with site-specific soil nutrient availability in Hawaiian rainforests. Above-ground plant litter and fine root litter was sampled across a substrate age gradient of a wide range in nitrogen and phosphorus availability using litter traps and soil cores. Total phenolic concentrations in leaf litter of the dominant tree species Metrosideros polymorpha was 65% higher at the P-limited site compared to the N-limited site. Leaf litter from two relatively fertile sites co-limited by N and P showed intermediate polyphenol concentrations. In contrast, fine root litter had the highest concentrations of total phenolics at the N-limited site and the lowest concentrations at the comparatively fertile sites. The differences in condensed tannin concentration among sites were less pronounced for leaf litter, but greater for fine root litter. Long-term fertilization did not significantly alter polyphenol concentrations in Metrosideros litter at either site. Polyphenol concentrations in green leaves and leaf litter of Metrosideros showed the same relative differences among sites when compared between natural populations and plants from the same populations but grown in a common garden. Our data suggest that differences in polyphenol concentration in Metrosideros among sites are inherent population characteristics that may reflect long-term adaptations to site-specific differences in nutrient availability.
KEY WORDS: polyphenols, soil nutrient availability, leaf and fine root litter, soil chronosequence