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.
Litter production, decomposition, and carbon and nitrogen dynamics along a wet tropical elevation gradient.
SILVER, WHENDEE1, THOMPSON, ANDREW1, 1
ABSTRACT- We measured litterfall productivity, litter quality, and decomposition at 12 sites along a tropical elevation (300 m) and temperature (2 oC ) gradient in the Luquillo Experimental Forest, Puerto Rico to examine the sensitivity of these processes to small, but systematic changes in temperature. Mean annual leaf litter production over a 5 yr period decreased linearly from 6 (± 0.06) Mg/ha/yr at the lower elevation to 0.6 (± 0.007) Mg/ha/yr at the upper elevation. Temperature explained up to 75 % of the variability in litter production, although there was significant interannual variability in this relationship. There were no elevational trends in litter decomposition rates (0.5 to 1.0 k yr-1), although there were significant differences among plant communities. Litter quality explained the greatest amount of variability in decomposition rates, particularly tissue CN ratios. We used a common substrate (craft sticks) to examine the effects of site quality on decomposition rates. From a decomposition perspective, the 12 sites could be grouped into two site qualities, those with palm and wet tropical forest vegetation, and those with short and tall rain forest vegetation. Decay of all tissues at two common sites highlighted the differential sensitivity of litter types to changes in environmental conditions. Our results indicate that litter production and decomposition are decoupled over relatively short time periods (2-5 yr), and are likely to be responding differently to climate change.
KEY WORDS: climate, temperature, soil carbon, nitrogen cycling