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Reconstructing Long-Term Flood Regimes with Rainfall Data: Effects of Flood Timing on Caddisfly Populations

David A. Lytle
The Southwestern Naturalist
Vol. 48, No. 1 (Mar., 2003), pp. 36-42
Stable URL: http://www.jstor.org/stable/3672735
Page Count: 7
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Reconstructing Long-Term Flood Regimes with Rainfall Data: Effects of Flood Timing on Caddisfly Populations
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Abstract

Flash floods are a defining feature of desert streams, but flow records are not always available to characterize long-term flood dynamics. In this study, rainfall data spanning 100 years were used as a proxy to quantify long-term flood regimes for southeastern Arizona (USA) streams. The frequency and seasonal timing of severe floods (>50% substrate movement) were highly variable at short temporal scales (days to several years), but clear patterns emerged in the long-term (several years to a century). To explore the ecological effects of flood timing, populations of the caddisfly Phylloicus aeneus (Calamoceratidae) were monitored in 2 streams over 3 years. The timing of individual floods relative to the long-term average strongly affected P. aeneus populations: early and timely floods had little effect on population size in the next year, but late floods significantly reduced population size in the next year. Thus, flood timing might play a role in regulating populations of desert stream organisms. /// Inundaciones repentinas son una característica distintiva de los arroyos de desierto, pero los datos hidrológicos no están siempre disponibles para caracterizar la dinámica de las inundaciones a largo plazo. En este estudio, datos de precipitación desde cien años atrás fueron utilizados como aproximación para cuantificar regímenes de inundación a largo plazo para arroyos del sudeste de Arizona, USA. La frecuencia y ocurrencia estacional de inundaciones severas (>50% movimiento de sustrato) fueron altamente variables a corto plazo (de días a varios años), pero modelos claros emergieron a largo plazo (varios años a un siglo). Para explorar los efectos ecológicos del patrón temporal de las inundaciones, las poblaciones de la tricóptera Phylloicus aeneus (Calamoceratidae) fueron monitoreadas en 2 arroyos durante 3 años. La ocurrencia temporal de inundaciones individuales en relación al promedio a largo plazo afectó fuertemente las poblaciones de P. aeneus: las inundaciones tempranas y oportunas tuvieron poco efecto en el tamaño poblacional del año siguiente, pero las inundaciones tardías redujeron significativamente el tamaño poblacional del año siguiente. De este modo, el patrón temporal de las inundaciones puede regular las poblaciones de organismos de arroyos de desierto.

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