Breakdown Rates of Tulip-poplar Leaves in Streams Draining Suburban Watersheds
Meyer, Judy L.
Shuman, Larry M.
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Leaf litter inputs are an integral part of stream food webs. Changes to this basic food resource from natural or anthropogenic causes can have repercussions at higher trophic levels. Stormwater runoff from residential lawns transports pesticides and fertilizers to stream ecosystems. This study measures leaf breakdown rates in two suburban streams in Peachtree City, Georgia, and considers if fungicide or nutrient concentrations have impacted those rates. Leaf breakdown rates in these suburban streams were compared with breakdown rates in two reference streams. We analyzed stream temperature and concentrations of ammonium, nitrate, soluble reactive phosphorus, and selected pesticides. Relationships between these parameters and breakdown rates of tulip-poplar leaves (Liriodendron tulipifera L.) were examined. Surprisingly, nitrate, ammonium and hydroxychlorothalonil (a fungicide degradation product) concentrations were somewhat higher in the reference streams. Leaf breakdown rates for the first seven weeks were similar in three streams and lower in one of the reference streams. Differences in nutrient and pesticide concentrations were not consistent and could not explain observed differences in leaf breakdown rates.