PARENT SESSION
Oral Session #46: Disturbance Ecology.
Presiding: M. Slocum
Tuesday, August 6. 1:00 PM to 4:45 PM. Grand Ballroom East, Radisson.
How flooding, via indirect effects, impacts the performance of a common riparian plant species, Mimulus guttatus.
Elderd, Bret*,1, 1 Department of Environmental Studies, Santa Cruz, CA
ABSTRACT- The impacts of disturbance on riparian plant communities can have many varied consequences with unforeseen effects. Lack of disturbance can also dramatically alter riparian plant communities. These potential impacts include the establishment of woody species along previously uninhabitable reaches of a stream and increased build up in leaf litter or thatch that, in the past, was washed away by high flow events. To study the impacts that the establishment of woody species via shading and the build up of leaf litter have on riparian areas, I examined the effects of increasing shade levels and leaf litter on the germination and growth of ,Mimulus guttatus, a common riparian plant, using both greenhouse and field experiments. Using a latin squares design for a series of greenhouse studies where I manipulated both shading and litter level, I found that there was a significant interaction between shading and litter (p<0.05) for both germination and growth measurements. In these experiments, plants in shaded pots with increased litter did worse as compared to other treatments. In the field, M. guttatus germination was also negatively affected by litter (p<0.005) and by an interaction between shading and the year the experiment was conducted (p<0.005), a corollary for differences in yearly rainfall. However, growth was positively affected by shading (p<0.05) and litter augmentation did not impact growth. In riparian areas where disturbance regimes have been altered, the impacts of these changes through differential reestablishment of woody species and build up of a litter layer can both directly and indirectly affect individual riparian plant species and may eventually alter community composition.
KEY WORDS: Shading, Leaf litter, Mimulus guttatus, Lack of Disturbance