Habitat complexity, spatial scale and grazing interactions in a temperate river

摘要: Complex habitat architecture is associated with high species richness and thought to weaken trophic interactions between species. This thesis examines the effect of different levels architectural complexity on strength interaction that exists algae invertebrate grazers in Mountain River, Tasmania. river contains two major riffle types, contrasting architecture: bedrock platforms, which have a very simple architecture, boulder-cobble riffles, are complex. Two spatial scales were studied: microhabitats riffles. The research strategy began one year stratified sampling types their for invertebrates. manipulative experiments then carried out determine scale epilithic grazers. Grazers removed from some experimental plots not others response was measured. followed by large experiment simultaneously compared microhabitat using artificial substrata. half substrates algal growth To observe role invertebrates spates, densities censused regularly before after small spate. The differences quantified fractal geometry. Invertebrate body size spectra constructed seasonal samples related changes dimension order whether had controlled animal sizes. dominant same habitats; however, higher more complex type, greater simpler type. More reduced grazer population population. Manipulation at indicated influence density than also determined outcome competition grazing Rock tops type flow refuge low magnitude flood events. riffles average showed absent platforms. These shape could be directly habitats. Habitat both therefore significant all aspects community structure function studied.