Title

Influence of stream channel form on leaf decomposition rates

Presenter Information

Mika Mulliken
Daniel Caris

Document Type

Oral Presentation

Location

SURC Ballroom C/D

Start Date

16-5-2013

End Date

16-5-2013

Abstract

Forested stream headwaters receive little light due to heavy shading, so leaves falling into the stream provide organic matter to fuel the food web. Leaf decomposition is an integrative ecosystem-level process that links abiotic and biotic characteristics. For example, most nutrients leach from the leaves within a few days of falling into the stream, leaving only cellulose and lignin. Animals cannot digest these compounds so fungi and bacteria breakdown this material, softening the leaves for aquatic insects called shredders. These organisms convert leaves to smaller material which becomes a food source for other organisms. The rate at which leaves decompose in streams and how efficiently the nutrients are cycled will contribute to the health of the stream. In cobble-bed streams, channel morphology can affect decomposition. Along a single stream segment, surface water enters a down-welling zone and moves into the sediment. This water flows beneath the stream and eventually upwells at a downstream point, bringing warmer and more nitrogen-rich water to the surface. Warmer temperatures and higher nitrogen concentrations can increase leaf decomposition rates. My objective is to compare decomposition rates of leaves in Taneum Creek. I selected six sites that each have a connected upwelling and down-welling zone. Each site has 18 leaf packs which will be sampled six times to calculate the decomposition rate as mass lost versus time. Water chemistry and temperature for each site will also be recorded. I hypothesize that upwelling sites will have faster decomposition rates because of higher nitrogen concentrations and warmer temperatures.

Poster Number

17

Faculty Mentor(s)

Clay Arango

Additional Mentoring Department

Environmental Studies

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May 16th, 2:15 PM May 16th, 4:44 PM

Influence of stream channel form on leaf decomposition rates

SURC Ballroom C/D

Forested stream headwaters receive little light due to heavy shading, so leaves falling into the stream provide organic matter to fuel the food web. Leaf decomposition is an integrative ecosystem-level process that links abiotic and biotic characteristics. For example, most nutrients leach from the leaves within a few days of falling into the stream, leaving only cellulose and lignin. Animals cannot digest these compounds so fungi and bacteria breakdown this material, softening the leaves for aquatic insects called shredders. These organisms convert leaves to smaller material which becomes a food source for other organisms. The rate at which leaves decompose in streams and how efficiently the nutrients are cycled will contribute to the health of the stream. In cobble-bed streams, channel morphology can affect decomposition. Along a single stream segment, surface water enters a down-welling zone and moves into the sediment. This water flows beneath the stream and eventually upwells at a downstream point, bringing warmer and more nitrogen-rich water to the surface. Warmer temperatures and higher nitrogen concentrations can increase leaf decomposition rates. My objective is to compare decomposition rates of leaves in Taneum Creek. I selected six sites that each have a connected upwelling and down-welling zone. Each site has 18 leaf packs which will be sampled six times to calculate the decomposition rate as mass lost versus time. Water chemistry and temperature for each site will also be recorded. I hypothesize that upwelling sites will have faster decomposition rates because of higher nitrogen concentrations and warmer temperatures.