PARENT SESSION
Oral Session #94: Nutrient Cycling.
Presiding: R. Yanai
Thursday, August 8. 1:00 PM to 3:45 PM. Grand Ballroom East, Radisson.

ENSO effects on leaf litter nutrient cycling in an old growth wet tropical forest in Costa Rica.

Wood, Tana^*,1, Lawrence, Deborah¹, Clark, Deborah², ¹ University of Virginia, Charlottesville² University of Missouri, St. Louis

ABSTRACT- The study of leaf litter nutrient cycling could provide important information on the potential response of wet tropical forests to environmental and climatic variability. Our goal was to assess whether an El Niño Southern Oscillation (ENSO) event would elicit a feedback response on the productivity and cycling of nutrients in a wet tropical forest. We analyzed both leaf litter P and N for 4 years, spanning the 1997 ENSO, in old growth forests at La Selva Biological Research Station in Costa Rica. We sampled 18 plots across the three main soil types: Ultisol slope, Ultisol plateau, and Inseptisol. Both P and N concentrations were consistently higher in the Inceptisols than in the Ultisols, with no significant difference between Ultisol slope and Ultisol plateau. We performed time-lag correlations between leaf litter nutrient concentrations and the amount of leaf litterfall as well as the total rainfall from 0-16 weeks previous, using 2-week time-lag intervals. Rainfall did not significantly correlate with leaf litter nutrient concentrations at any of the selected time lags. The correlations between nutrient concentrations and litterfall were not significant for the first 8 weeks. However, Ultisol P concentrations and litterfall amount were significantly correlated from 10 to 16 weeks (3-4 months) (p<0.05, r_10wk=0.21, r,_12wk= 0.27, r_14wk= 0.38, r_16wk= 0.26), while the Inceptisol nutrient concentrations were not significantly correlated with litterfall at any of the selected time lags. We would suggest that both the quality and quantity of leaf litterfall affect subsequent leaf litter nutrient concentrations within a 3-4 months.

KEY WORDS: ENSO, leaf litter, nutrient cycling, tropical