HR: 09:45h
AN: NB41B-06    [Abstracts]
TI: Annual Variation in Climatic Conditions and Leaf Litter Inputs Into Two Tropical Dry Forest Streams -- a Response to the El Nino Southern Oscillation (ENSO)
AU: * Jackson, J K
EM: jkjackson@stroudcenter.org
AF: Stroud Water Research Center, 970 Spencer Road, Avondale, PA 19311 United States
AU: Sweeney, B W
EM: sweeney@stroudcenter.org
AF: Stroud Water Research Center, 970 Spencer Road, Avondale, PA 19311 United States
AU: Newbold, J D
EM: newbold@stroudcenter.org
AF: Stroud Water Research Center, 970 Spencer Road, Avondale, PA 19311 United States
AB: Tropical dry forests are defined by a severe seasonal drought that results from warm air temperature and extremely seasonal rainfall. We measured daily air temperature, rainfall, and leaf litterfall from 1991-2004 at a dry forest site in northwestern Costa Rica. Rainfall ranged from 1-121 mm in the driest month (April) to 185-1051 mm in the wettest month (October). Annual rainfall ranged from 2229-3676 mm. Air temperature varied little (6.7°C diel, 1.5°C interannual). Annual climatic differences appear related to ENSO conditions - El Nino years are 1-2°C warmer and receive 1400 mm less rainfall than La Nina years. Monthly litterfall collected with wire baskets suspended over two nearby streams ranged from 30-136 g AFDM/m² while annual litterfall ranged from 714-968 g/m². Leaves comprised 78% of litterfall. Annual litterfall during El Nino years was 30% greater (250 g/m²) than during La Nina years, presumably because greater moisture stress increased leaf shedding from streamside forests. This increase was only apparent during the driest months (February-May). These results suggest that annual variation in allochthonous organic matter input into these streams reflects, in part, a response to the ENSO - a large-scale climatic phenomenon with a multi-year return interval.
DE: 9810 New fields (not classifiable under other headings)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly