This doctoral dissertation improvement project will use high-resolution remotely sensed data from aircraft to map plant species distributions and vegetation structure in the mediterranean-type ecosystem of Santa Cruz Island, California. The project will test the hypothesis that heterogeneity in plant occurrences is explained by both environmental variables and the dispersal abilities of the plants and that the relative importance of environment vs. dispersal will be related to the spatial scale at which the plant communities are examined.
This work will contribute to the further development of techniques to assess fine-scale detail of plant communities from remotely-sensed data. It will also contribute to our understanding of processes determining plant species distributions, which is important for developing effective restoration and conservation projects.
In this Doctoral Dissertation Improvement Grant we proposed to use high resolution airborne remote sensing data from the Carnegie Airborne Observatory (CAO) to consider the importance of scale to vegetation patterns on Santa Cruz Island, California. Using the CAO measures of greenness (from the hyperspectral data), vegetation height (from LiDAR), and a geostatistical approach called simultaneous autoregressive modeling (SAR) we found that environmental gradients explained a small amount of the vegetation patterns, but that there was a consistent scale of spatial autocorrelation at 600-700 m. Interestingly, this scale corresponds closely to the home range sizes of the two key seed dispersers on the island – the Santa Cruz Island fox (Urocyon littoralis santacruzae) and the island scrub-jay (Aphelocoma insularis). Both of these species have been the focus of recent conservation efforts, and so this result is of particular interest to the islandâ€™s managing organizations (The Nature Conservancy and the National Park Service). In addition this work involved the participation of one undergraduate student, who learned geographic information science, GPS navigation, and basic ecological field methods. This award allowed Co-PI Dahlin and the undergraduate student to spend three weeks on Santa Cruz Island collecting data about plant distributions and generating hypotheses for future work. The primary products of this award were a chapter of Co-PI Dahlinâ€™s dissertation (completed in August 2012) and a manuscript that is currently in review.