PARENT SESSION
Contributed Oral Session 72: Trophic Systems: Communities; Predator Behavior
Tuesday, August 9, 1:30 PM - 5:00 PM, Meeting Room 524 C, Level 5, Palais des congrès de Montréal

The effects of introduced predators on island plant communities: a comparison at multiple spatial and temporal scales.

Danner, Eric¹, ¹ University of California Santa Cruz, Santa Cruz, CA, USA

ABSTRACT- Recent work by Croll et al. (Science, in press) has demonstrated that introduced foxes in the Aleutian archipelago initiated an ecosystem-wide trophic cascade that reduced the transport of nutrients from ocean to land, created nutrient-impoverished soils, and transformed terrestrial grasslands to dwarf shrub/forb-dominated ecosystems. Their results were based on a standard point method of vegetation sampling during a single time of year (August). I have examined this system at larger spatial scales (across entire islands and the entire archipelago) and at multiple temporal scales (every 16 days from 2000 through 2004) using remotely sensed data. Vegetation indices (MODIS 250m NDVI and EVI) were used to estimate plant biomass and phenological patterns such as start of growing season (SOS), end of growing season (EOS), and growing season length (GSL). Results indicate complex relationships between VI values and bird densities, each islands physical parameters, and the presence/absence of foxes. In general, grass dominated communities on fox-free islands have seasonally distinct VI characteristics (such as earlier SOS, higher maximum values) in contrast to dwarf shrub/forb dominated communities on fox-infested islands. The remote sensing approach allows for the examination of patterns in space and time that would not be possible using conventional ground-based methods.

Key words: trophic cascades, remote sensing, spatial scale