PARENT SESSION
Oral Session #67: Metapopulations, fragmented landscapes, and patch dynamics. Presiding: C. Kraft.
Thursday, August 9, 2001. 1:00 PM to 4:30 PM. Hall of Ideas F.
Effect of subdivision of resource patches on mobile fauna in dynamic streambed landscapes.
SILVER, PAMELA1, PALMER, MARGARET 2, WOOSTER, DAVID2, 1 2
ABSTRACT- Habitat fragmentation frequently is accompanied by habitat loss, confounding the effects of fragmentation and loss on the abundance or diversity of organisms in a landscape. To isolate the effects of habitat fragmentation on the abundances of stream meiofauna in leafy debris, we held the amount of habitat constant and manipulated the arrangement and species of leaves in 2 x 5 m uncaged landscapes in a sandy-bottom stream. On sandy streambeds, leafy debris forms natural landscapes that range from highly aggregated to strongly subdivided. Meiofauna are assumed to be unresponsive to the arrangement but highly responsive to the decomposition rate of the leaves. We removed ambient CPOM from each landscape and replaced it with 189 pairs of leaves tethered to buried dowels. Refractory, labile, or mixed leaves were arranged into 7 large or 63 small patches. Chironomids were significantly more abundant on leaves in "subdivided" than in "aggregated" landscapes and significantly less abundant on leaves in landscapes with mixed rather than refractory or labile leaves. The results of this field-based experiment are counter to commonly-held paradigms in stream and landscape ecology. However, they agree with our descriptive field work, laboratory experiments, and modeling, which show that meiofauna prefer landscapes in which resources are subdivided among many small patches. We speculate that subdivision of resources may increase the likelihood of dispersing animals encountering resource patches in dynamic landscapes such as streambeds.
KEY WORDS: chironomid, habitat fragmentation, streambed landscape, leafy debris patch