PARENT SESSION
Poster Session #19: Nutrient Cycling.
Tuesday, August 7, 2001. Presentation from 3:30 PM to 5:00 PM. Exhibition Hall
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ENSO effects on litter phosphorus dynamics across three edaphic types in wet tropical forests of northeastern Costa Rica.
Wood, Tana1, Lawrence, Deborah1, Clark, Deborah2, 1 2
ABSTRACT- The functioning of tropical ecosystems can be affected by changes in climatic conditions through processes related to nutrient assimilation. Our goal was to assess whether an El Niño Southern Oscillation event would elicit a feedback response on the productivity and Phosphorous cycling of a wet tropical forest. We analyzed leaf litter P for 2 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 edaphic types: Ultisol slope, Ultisol plateau, and Inseptisol. The P content ranged from 0.55-0.8 in Ultisol plateaus, 0.58-0.74 in Ultisol slopes and 0.69-1.04 in Inceptisols. Phosphorous was consistently higher in the Inceptisols than in the Ultisols. The P peak for all three edaphic types occurred in June 1999 and the low in November 1998. During the ENSO year, leaf litter production increased by 10-20%. During this period, P concentration remained constant from the wet to dry season; however, leaf litter P increased significantly during the wet season immediately following the ENSO year (p<0.002) and was still elevated the following dry season (p<0.09). We suggest that the increase in litter production in 1997-8 caused a significant increase in litter P content within 6 months, demonstrating rapid feedbacks between climate and vegetation and a positive effect on productivity that persisted for a year.
KEY WORDS: Tropical, Edaphic, Phosphorous, ENSO